From 31ca32539612d39165cd8551df6c6357984b3fef Mon Sep 17 00:00:00 2001
From: Fendor <power.walross@gmail.com>
Date: Fri, 2 Feb 2024 17:25:01 +0100
Subject: [PATCH] Revert "Drop sub-component targets (#8966)"

This reverts commit 3f4c81fd7936fa6dcdcac833ae42cc4158b1823a.
---
 Cabal/src/Distribution/Simple/BuildTarget.hs  | 400 ++++++++++--
 cabal-install/cabal-install.cabal             |   1 +
 .../src/Distribution/Client/CmdBench.hs       |  37 +-
 .../src/Distribution/Client/CmdBuild.hs       |   3 +-
 .../Distribution/Client/CmdErrorMessages.hs   |  31 +-
 .../src/Distribution/Client/CmdHaddock.hs     |   3 +-
 .../src/Distribution/Client/CmdInstall.hs     |  11 +-
 .../CmdInstall/ClientInstallTargetSelector.hs |   2 +-
 .../src/Distribution/Client/CmdListBin.hs     |  36 +-
 .../src/Distribution/Client/CmdRepl.hs        |   3 +-
 .../src/Distribution/Client/CmdRun.hs         |  36 +-
 .../src/Distribution/Client/CmdSdist.hs       |   4 +-
 .../src/Distribution/Client/CmdTest.hs        |  37 +-
 .../ProjectBuilding/PackageFileMonitor.hs     |  11 +-
 .../Client/ProjectBuilding/UnpackedPackage.hs |   2 +-
 .../Client/ProjectOrchestration.hs            |  50 +-
 .../Distribution/Client/ProjectPlanning.hs    |  32 +-
 .../Client/ProjectPlanning/Types.hs           |  34 +-
 .../src/Distribution/Client/TargetProblem.hs  |   6 +-
 .../src/Distribution/Client/TargetSelector.hs | 584 +++++++++++++++++-
 cabal-install/tests/IntegrationTests2.hs      | 136 +++-
 cabal-install/tests/UnitTests.hs              |   4 +
 .../Distribution/Client/ProjectPlanning.hs    |  90 +++
 .../NewBuild/CmdRun/RunMainBad/Main.hs        |   1 +
 .../CmdRun/RunMainBad/RunMainBad.cabal        |   9 +
 .../NewBuild/CmdRun/RunMainBad/cabal.out      |   4 +
 .../NewBuild/CmdRun/RunMainBad/cabal.project  |   1 +
 .../NewBuild/CmdRun/RunMainBad/cabal.test.hs  |   4 +
 changelog.d/pr-8966                           |  20 -
 29 files changed, 1409 insertions(+), 183 deletions(-)
 create mode 100644 cabal-install/tests/UnitTests/Distribution/Client/ProjectPlanning.hs
 create mode 100644 cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/Main.hs
 create mode 100644 cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/RunMainBad.cabal
 create mode 100644 cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.out
 create mode 100644 cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.project
 create mode 100644 cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.test.hs
 delete mode 100644 changelog.d/pr-8966

diff --git a/Cabal/src/Distribution/Simple/BuildTarget.hs b/Cabal/src/Distribution/Simple/BuildTarget.hs
index caaeb42eefe..06b387c04ae 100644
--- a/Cabal/src/Distribution/Simple/BuildTarget.hs
+++ b/Cabal/src/Distribution/Simple/BuildTarget.hs
@@ -25,6 +25,7 @@ module Distribution.Simple.BuildTarget
   , BuildTarget (..)
   , showBuildTarget
   , QualLevel (..)
+  , buildTargetComponentName
 
     -- * Parsing user build targets
   , UserBuildTarget
@@ -61,9 +62,19 @@ import Distribution.Utils.Path
 import Distribution.Verbosity
 
 import Control.Arrow ((&&&))
-import Data.List (groupBy)
+import Control.Monad (msum)
+import Data.List (groupBy, stripPrefix)
 import qualified Data.List.NonEmpty as NE
 import qualified Data.Map as Map
+import System.Directory (doesDirectoryExist, doesFileExist)
+import System.FilePath as FilePath
+  ( dropExtension
+  , hasTrailingPathSeparator
+  , joinPath
+  , normalise
+  , splitDirectories
+  , splitPath
+  )
 
 -- | Take a list of 'String' build targets, and parse and validate them
 -- into actual 'TargetInfo's to be built/registered/whatever.
@@ -80,15 +91,27 @@ readTargetInfos verbosity pkg_descr lbi args = do
 
 -- | Various ways that a user may specify a build target.
 data UserBuildTarget
-  = -- | A target specified by a component name.
+  = -- | A target specified by a single name. This could be a component
+    -- module or file.
     --
     -- > cabal build foo
+    -- > cabal build Data.Foo
+    -- > cabal build Data/Foo.hs  Data/Foo.hsc
     UserBuildTargetSingle String
-  | -- | A target specified by a component kind and a component name.
+  | -- | A target specified by a qualifier and name. This could be a component
+    -- name qualified by the component namespace kind, or a module or file
+    -- qualified by the component name.
     --
-    -- > cabal build lib:foo
-    -- > cabal build test:foo-test
+    -- > cabal build lib:foo exe:foo
+    -- > cabal build foo:Data.Foo
+    -- > cabal build foo:Data/Foo.hs
     UserBuildTargetDouble String String
+  | -- | A fully qualified target, either a module or file qualified by a
+    -- component name with the component namespace kind.
+    --
+    -- > cabal build lib:foo:Data/Foo.hs exe:foo:Data/Foo.hs
+    -- > cabal build lib:foo:Data.Foo exe:foo:Data.Foo
+    UserBuildTargetTriple String String String
   deriving (Show, Eq, Ord)
 
 -- ------------------------------------------------------------
@@ -101,10 +124,19 @@ data UserBuildTarget
 data BuildTarget
   = -- | A specific component
     BuildTargetComponent ComponentName
+  | -- | A specific module within a specific component.
+    BuildTargetModule ComponentName ModuleName
+  | -- | A specific file within a specific component.
+    BuildTargetFile ComponentName FilePath
   deriving (Eq, Show, Generic)
 
 instance Binary BuildTarget
 
+buildTargetComponentName :: BuildTarget -> ComponentName
+buildTargetComponentName (BuildTargetComponent cn) = cn
+buildTargetComponentName (BuildTargetModule cn _) = cn
+buildTargetComponentName (BuildTargetFile cn _) = cn
+
 -- | Read a list of user-supplied build target strings and resolve them to
 -- 'BuildTarget's according to a 'PackageDescription'. If there are problems
 -- with any of the targets e.g. they don't exist or are misformatted, throw an
@@ -114,11 +146,29 @@ readBuildTargets verbosity pkg targetStrs = do
   let (uproblems, utargets) = readUserBuildTargets targetStrs
   reportUserBuildTargetProblems verbosity uproblems
 
-  let (bproblems, btargets) = resolveBuildTargets pkg utargets
+  utargets' <- traverse checkTargetExistsAsFile utargets
+
+  let (bproblems, btargets) = resolveBuildTargets pkg utargets'
   reportBuildTargetProblems verbosity bproblems
 
   return btargets
 
+checkTargetExistsAsFile :: UserBuildTarget -> IO (UserBuildTarget, Bool)
+checkTargetExistsAsFile t = do
+  fexists <- existsAsFile (fileComponentOfTarget t)
+  return (t, fexists)
+  where
+    existsAsFile f = do
+      exists <- doesFileExist f
+      case splitPath f of
+        (d : _) | hasTrailingPathSeparator d -> doesDirectoryExist d
+        (d : _ : _) | not exists -> doesDirectoryExist d
+        _ -> return exists
+
+    fileComponentOfTarget (UserBuildTargetSingle s1) = s1
+    fileComponentOfTarget (UserBuildTargetDouble _ s2) = s2
+    fileComponentOfTarget (UserBuildTargetTriple _ _ s3) = s3
+
 -- ------------------------------------------------------------
 
 -- * Parsing user targets
@@ -140,8 +190,8 @@ readUserBuildTargets = partitionEithers . map readUserBuildTarget
 -- >>> readUserBuildTarget "lib:comp"
 -- Right (UserBuildTargetDouble "lib" "comp")
 --
--- >>> readUserBuildTarget "else:comp"
--- Right (UserBuildTargetDouble "else" "comp")
+-- >>> readUserBuildTarget "pkg:lib:comp"
+-- Right (UserBuildTargetTriple "pkg" "lib" "comp")
 --
 -- >>> readUserBuildTarget "\"comp\""
 -- Right (UserBuildTargetSingle "comp")
@@ -149,8 +199,14 @@ readUserBuildTargets = partitionEithers . map readUserBuildTarget
 -- >>> readUserBuildTarget "lib:\"comp\""
 -- Right (UserBuildTargetDouble "lib" "comp")
 --
--- >>> readUserBuildTarget "one:two:three"
--- Left (UserBuildTargetUnrecognised "one:two:three")
+-- >>> readUserBuildTarget "pkg:lib:\"comp\""
+-- Right (UserBuildTargetTriple "pkg" "lib" "comp")
+--
+-- >>> readUserBuildTarget "pkg:lib:comp:more"
+-- Left (UserBuildTargetUnrecognised "pkg:lib:comp:more")
+--
+-- >>> readUserBuildTarget "pkg:\"lib\":comp"
+-- Left (UserBuildTargetUnrecognised "pkg:\"lib\":comp")
 readUserBuildTarget
   :: String
   -> Either
@@ -167,15 +223,18 @@ readUserBuildTarget targetstr =
       ts <- tokens
       return $ case ts of
         (a, Nothing) -> UserBuildTargetSingle a
-        (a, Just b) -> UserBuildTargetDouble a b
+        (a, Just (b, Nothing)) -> UserBuildTargetDouble a b
+        (a, Just (b, Just c)) -> UserBuildTargetTriple a b c
 
-    tokens :: CabalParsing m => m (String, Maybe String)
+    tokens :: CabalParsing m => m (String, Maybe (String, Maybe String))
     tokens =
-      (\s -> (s, Nothing))
-        <$> parsecHaskellString
-        <|> (,)
-          <$> token
-          <*> P.optional (P.char ':' *> (parsecHaskellString <|> token))
+      (\s -> (s, Nothing)) <$> parsecHaskellString
+        <|> (,) <$> token <*> P.optional (P.char ':' *> tokens2)
+
+    tokens2 :: CabalParsing m => m (String, Maybe String)
+    tokens2 =
+      (\s -> (s, Nothing)) <$> parsecHaskellString
+        <|> (,) <$> token <*> P.optional (P.char ':' *> (parsecHaskellString <|> token))
 
     token :: CabalParsing m => m String
     token = P.munch1 (\x -> not (isSpace x) && x /= ':')
@@ -197,12 +256,22 @@ showUserBuildTarget = intercalate ":" . getComponents
   where
     getComponents (UserBuildTargetSingle s1) = [s1]
     getComponents (UserBuildTargetDouble s1 s2) = [s1, s2]
+    getComponents (UserBuildTargetTriple s1 s2 s3) = [s1, s2, s3]
+
+-- | Unless you use 'QL1', this function is PARTIAL;
+-- use 'showBuildTarget' instead.
+showBuildTarget' :: QualLevel -> PackageId -> BuildTarget -> String
+showBuildTarget' ql pkgid bt =
+  showUserBuildTarget (renderBuildTarget ql bt pkgid)
 
 -- | Unambiguously render a 'BuildTarget', so that it can
 -- be parsed in all situations.
 showBuildTarget :: PackageId -> BuildTarget -> String
 showBuildTarget pkgid t =
-  showUserBuildTarget (renderBuildTarget QL2 t pkgid)
+  showBuildTarget' (qlBuildTarget t) pkgid t
+  where
+    qlBuildTarget BuildTargetComponent{} = QL2
+    qlBuildTarget _ = QL3
 
 -- ------------------------------------------------------------
 
@@ -228,18 +297,19 @@ Just ex_pkgid = simpleParse "thelib"
 -- refer to.
 resolveBuildTargets
   :: PackageDescription
-  -> [UserBuildTarget]
+  -> [(UserBuildTarget, Bool)]
   -> ([BuildTargetProblem], [BuildTarget])
 resolveBuildTargets pkg =
   partitionEithers
-    . map (resolveBuildTarget pkg)
+    . map (uncurry (resolveBuildTarget pkg))
 
 resolveBuildTarget
   :: PackageDescription
   -> UserBuildTarget
+  -> Bool
   -> Either BuildTargetProblem BuildTarget
-resolveBuildTarget pkg userTarget =
-  case findMatch (matchBuildTarget pkg userTarget) of
+resolveBuildTarget pkg userTarget fexists =
+  case findMatch (matchBuildTarget pkg userTarget fexists) of
     Unambiguous target -> Right target
     Ambiguous targets -> Left (BuildTargetAmbiguous userTarget targets')
       where
@@ -285,6 +355,7 @@ disambiguateBuildTargets pkgid original =
 
     userTargetQualLevel (UserBuildTargetSingle _) = QL1
     userTargetQualLevel (UserBuildTargetDouble _ _) = QL2
+    userTargetQualLevel (UserBuildTargetTriple _ _ _) = QL3
 
     step
       :: QualLevel
@@ -297,7 +368,7 @@ disambiguateBuildTargets pkgid original =
         . sortBy (comparing fst)
         . map (\t -> (renderBuildTarget ql t pkgid, t))
 
-data QualLevel = QL1 | QL2
+data QualLevel = QL1 | QL2 | QL3
   deriving (Enum, Show)
 
 renderBuildTarget :: QualLevel -> BuildTarget -> PackageId -> UserBuildTarget
@@ -305,10 +376,19 @@ renderBuildTarget ql target pkgid =
   case ql of
     QL1 -> UserBuildTargetSingle s1 where s1 = single target
     QL2 -> UserBuildTargetDouble s1 s2 where (s1, s2) = double target
+    QL3 -> UserBuildTargetTriple s1 s2 s3 where (s1, s2, s3) = triple target
   where
     single (BuildTargetComponent cn) = dispCName cn
+    single (BuildTargetModule _ m) = prettyShow m
+    single (BuildTargetFile _ f) = f
 
     double (BuildTargetComponent cn) = (dispKind cn, dispCName cn)
+    double (BuildTargetModule cn m) = (dispCName cn, prettyShow m)
+    double (BuildTargetFile cn f) = (dispCName cn, f)
+
+    triple (BuildTargetComponent _) = error "triple BuildTargetComponent"
+    triple (BuildTargetModule cn m) = (dispKind cn, dispCName cn, prettyShow m)
+    triple (BuildTargetFile cn f) = (dispKind cn, dispCName cn, f)
 
     dispCName = componentStringName pkgid
     dispKind = showComponentKindShort . componentKind
@@ -343,6 +423,8 @@ reportBuildTargetProblems verbosity problems = do
             targets
   where
     showBuildTargetKind (BuildTargetComponent _) = "component"
+    showBuildTargetKind (BuildTargetModule _ _) = "module"
+    showBuildTargetKind (BuildTargetFile _ _) = "file"
 
 ----------------------------------
 -- Top level BuildTarget matcher
@@ -351,16 +433,47 @@ reportBuildTargetProblems verbosity problems = do
 matchBuildTarget
   :: PackageDescription
   -> UserBuildTarget
+  -> Bool
   -> Match BuildTarget
-matchBuildTarget pkg utarget =
+matchBuildTarget pkg = \utarget fexists ->
   case utarget of
     UserBuildTargetSingle str1 ->
-      matchComponent1 cinfo str1
+      matchBuildTarget1 cinfo str1 fexists
     UserBuildTargetDouble str1 str2 ->
-      matchComponent2 cinfo str1 str2
+      matchBuildTarget2 cinfo str1 str2 fexists
+    UserBuildTargetTriple str1 str2 str3 ->
+      matchBuildTarget3 cinfo str1 str2 str3 fexists
   where
     cinfo = pkgComponentInfo pkg
 
+matchBuildTarget1 :: [ComponentInfo] -> String -> Bool -> Match BuildTarget
+matchBuildTarget1 cinfo str1 fexists =
+  matchComponent1 cinfo str1
+    `matchPlusShadowing` matchModule1 cinfo str1
+    `matchPlusShadowing` matchFile1 cinfo str1 fexists
+
+matchBuildTarget2
+  :: [ComponentInfo]
+  -> String
+  -> String
+  -> Bool
+  -> Match BuildTarget
+matchBuildTarget2 cinfo str1 str2 fexists =
+  matchComponent2 cinfo str1 str2
+    `matchPlusShadowing` matchModule2 cinfo str1 str2
+    `matchPlusShadowing` matchFile2 cinfo str1 str2 fexists
+
+matchBuildTarget3
+  :: [ComponentInfo]
+  -> String
+  -> String
+  -> String
+  -> Bool
+  -> Match BuildTarget
+matchBuildTarget3 cinfo str1 str2 str3 fexists =
+  matchModule3 cinfo str1 str2 str3
+    `matchPlusShadowing` matchFile3 cinfo str1 str2 str3 fexists
+
 data ComponentInfo = ComponentInfo
   { cinfoName :: ComponentName
   , cinfoStrName :: ComponentStringName
@@ -515,7 +628,11 @@ guardComponentName s
   | otherwise = matchErrorExpected "component name" s
   where
     validComponentChar c =
-      isAlphaNum c || c `elem` "._-'"
+      isAlphaNum c
+        || c == '.'
+        || c == '_'
+        || c == '-'
+        || c == '\''
 
 matchComponentName :: [ComponentInfo] -> String -> Match ComponentInfo
 matchComponentName cs str =
@@ -539,6 +656,180 @@ matchComponentKindAndName cs ckind str =
         [((cinfoKind c, cinfoStrName c), c) | c <- cs]
         (ckind, str)
 
+------------------------------
+-- Matching module targets
+--
+
+matchModule1 :: [ComponentInfo] -> String -> Match BuildTarget
+matchModule1 cs = \str1 -> do
+  guardModuleName str1
+  nubMatchErrors $ do
+    c <- tryEach cs
+    let ms = cinfoModules c
+    m <- matchModuleName ms str1
+    return (BuildTargetModule (cinfoName c) m)
+
+matchModule2 :: [ComponentInfo] -> String -> String -> Match BuildTarget
+matchModule2 cs = \str1 str2 -> do
+  guardComponentName str1
+  guardModuleName str2
+  c <- matchComponentName cs str1
+  let ms = cinfoModules c
+  m <- matchModuleName ms str2
+  return (BuildTargetModule (cinfoName c) m)
+
+matchModule3
+  :: [ComponentInfo]
+  -> String
+  -> String
+  -> String
+  -> Match BuildTarget
+matchModule3 cs str1 str2 str3 = do
+  ckind <- matchComponentKind str1
+  guardComponentName str2
+  c <- matchComponentKindAndName cs ckind str2
+  guardModuleName str3
+  let ms = cinfoModules c
+  m <- matchModuleName ms str3
+  return (BuildTargetModule (cinfoName c) m)
+
+-- utils:
+
+guardModuleName :: String -> Match ()
+guardModuleName s
+  | all validModuleChar s
+      && not (null s) =
+      increaseConfidence
+  | otherwise = matchErrorExpected "module name" s
+  where
+    validModuleChar c = isAlphaNum c || c == '.' || c == '_' || c == '\''
+
+matchModuleName :: [ModuleName] -> String -> Match ModuleName
+matchModuleName ms str =
+  orNoSuchThing "module" str $
+    increaseConfidenceFor $
+      matchInexactly
+        caseFold
+        [ (prettyShow m, m)
+        | m <- ms
+        ]
+        str
+
+------------------------------
+-- Matching file targets
+--
+
+matchFile1 :: [ComponentInfo] -> String -> Bool -> Match BuildTarget
+matchFile1 cs str1 exists =
+  nubMatchErrors $ do
+    c <- tryEach cs
+    filepath <- matchComponentFile c str1 exists
+    return (BuildTargetFile (cinfoName c) filepath)
+
+matchFile2 :: [ComponentInfo] -> String -> String -> Bool -> Match BuildTarget
+matchFile2 cs str1 str2 exists = do
+  guardComponentName str1
+  c <- matchComponentName cs str1
+  filepath <- matchComponentFile c str2 exists
+  return (BuildTargetFile (cinfoName c) filepath)
+
+matchFile3
+  :: [ComponentInfo]
+  -> String
+  -> String
+  -> String
+  -> Bool
+  -> Match BuildTarget
+matchFile3 cs str1 str2 str3 exists = do
+  ckind <- matchComponentKind str1
+  guardComponentName str2
+  c <- matchComponentKindAndName cs ckind str2
+  filepath <- matchComponentFile c str3 exists
+  return (BuildTargetFile (cinfoName c) filepath)
+
+matchComponentFile :: ComponentInfo -> String -> Bool -> Match FilePath
+matchComponentFile c str fexists =
+  expecting "file" str $
+    matchPlus
+      (matchFileExists str fexists)
+      ( matchPlusShadowing
+          ( msum
+              [ matchModuleFileRooted dirs ms str
+              , matchOtherFileRooted dirs hsFiles str
+              ]
+          )
+          ( msum
+              [ matchModuleFileUnrooted ms str
+              , matchOtherFileUnrooted hsFiles str
+              , matchOtherFileUnrooted cFiles str
+              , matchOtherFileUnrooted jsFiles str
+              ]
+          )
+      )
+  where
+    dirs = cinfoSrcDirs c
+    ms = cinfoModules c
+    hsFiles = cinfoHsFiles c
+    cFiles = cinfoCFiles c
+    jsFiles = cinfoJsFiles c
+
+-- utils
+
+matchFileExists :: FilePath -> Bool -> Match a
+matchFileExists _ False = mzero
+matchFileExists fname True = do
+  increaseConfidence
+  matchErrorNoSuch "file" fname
+
+matchModuleFileUnrooted :: [ModuleName] -> String -> Match FilePath
+matchModuleFileUnrooted ms str = do
+  let filepath = normalise str
+  _ <- matchModuleFileStem ms filepath
+  return filepath
+
+matchModuleFileRooted :: [FilePath] -> [ModuleName] -> String -> Match FilePath
+matchModuleFileRooted dirs ms str = nubMatches $ do
+  let filepath = normalise str
+  filepath' <- matchDirectoryPrefix dirs filepath
+  _ <- matchModuleFileStem ms filepath'
+  return filepath
+
+matchModuleFileStem :: [ModuleName] -> FilePath -> Match ModuleName
+matchModuleFileStem ms =
+  increaseConfidenceFor
+    . matchInexactly
+      caseFold
+      [(toFilePath m, m) | m <- ms]
+    . dropExtension
+
+matchOtherFileRooted :: [FilePath] -> [FilePath] -> FilePath -> Match FilePath
+matchOtherFileRooted dirs fs str = do
+  let filepath = normalise str
+  filepath' <- matchDirectoryPrefix dirs filepath
+  _ <- matchFile fs filepath'
+  return filepath
+
+matchOtherFileUnrooted :: [FilePath] -> FilePath -> Match FilePath
+matchOtherFileUnrooted fs str = do
+  let filepath = normalise str
+  _ <- matchFile fs filepath
+  return filepath
+
+matchFile :: [FilePath] -> FilePath -> Match FilePath
+matchFile fs =
+  increaseConfidenceFor
+    . matchInexactly caseFold [(f, f) | f <- fs]
+
+matchDirectoryPrefix :: [FilePath] -> FilePath -> Match FilePath
+matchDirectoryPrefix dirs filepath =
+  exactMatches $
+    catMaybes
+      [stripDirectory (normalise dir) filepath | dir <- dirs]
+  where
+    stripDirectory :: FilePath -> FilePath -> Maybe FilePath
+    stripDirectory dir fp =
+      joinPath `fmap` stripPrefix (splitDirectories dir) (splitDirectories fp)
+
 ------------------------------
 -- Matching monad
 --
@@ -592,6 +883,13 @@ matchPlus a@(NoMatch d1 ms) b@(NoMatch d2 ms')
   | d1 < d2 = b
   | otherwise = NoMatch d1 (ms ++ ms')
 
+-- | Combine two matchers. This is similar to 'ambiguousWith' with the
+-- difference that an exact match from the left matcher shadows any exact
+-- match on the right. Inexact matches are still collected however.
+matchPlusShadowing :: Match a -> Match a -> Match a
+matchPlusShadowing a@(ExactMatch _ _) (ExactMatch _ _) = a
+matchPlusShadowing a b = matchPlus a b
+
 instance Functor Match where
   fmap _ (NoMatch d ms) = NoMatch d ms
   fmap f (ExactMatch d xs) = ExactMatch d (fmap f xs)
@@ -609,9 +907,8 @@ instance Monad Match where
     addDepth d $
       foldr matchPlus matchZero (map f xs)
   InexactMatch d xs >>= f =
-    addDepth d
-      . forceInexact
-      $ foldr matchPlus matchZero (map f xs)
+    addDepth d . forceInexact $
+      foldr matchPlus matchZero (map f xs)
 
 addDepth :: Confidence -> Match a -> Match a
 addDepth d' (NoMatch d msgs) = NoMatch (d' + d) msgs
@@ -630,6 +927,10 @@ matchErrorExpected, matchErrorNoSuch :: String -> String -> Match a
 matchErrorExpected thing got = NoMatch 0 [MatchErrorExpected thing got]
 matchErrorNoSuch thing got = NoMatch 0 [MatchErrorNoSuch thing got]
 
+expecting :: String -> String -> Match a -> Match a
+expecting thing got (NoMatch 0 _) = matchErrorExpected thing got
+expecting _ _ m = m
+
 orNoSuchThing :: String -> String -> Match a -> Match a
 orNoSuchThing thing got (NoMatch 0 _) = matchErrorNoSuch thing got
 orNoSuchThing _ _ m = m
@@ -640,15 +941,26 @@ increaseConfidence = ExactMatch 1 [()]
 increaseConfidenceFor :: Match a -> Match a
 increaseConfidenceFor m = m >>= \r -> increaseConfidence >> return r
 
+nubMatches :: Eq a => Match a -> Match a
+nubMatches (NoMatch d msgs) = NoMatch d msgs
+nubMatches (ExactMatch d xs) = ExactMatch d (nub xs)
+nubMatches (InexactMatch d xs) = InexactMatch d (nub xs)
+
+nubMatchErrors :: Match a -> Match a
+nubMatchErrors (NoMatch d msgs) = NoMatch d (nub msgs)
+nubMatchErrors (ExactMatch d xs) = ExactMatch d xs
+nubMatchErrors (InexactMatch d xs) = InexactMatch d xs
+
 -- | Lift a list of matches to an exact match.
-exactMatches :: [a] -> Match a
+exactMatches, inexactMatches :: [a] -> Match a
 exactMatches [] = matchZero
 exactMatches xs = ExactMatch 0 xs
-
-inexactMatches :: [a] -> Match a
 inexactMatches [] = matchZero
 inexactMatches xs = InexactMatch 0 xs
 
+tryEach :: [a] -> Match a
+tryEach = exactMatches
+
 ------------------------------
 -- Top level match runner
 --
@@ -739,9 +1051,10 @@ checkBuildTargets
     let (enabled, disabled) =
           partitionEithers
             [ case componentDisabledReason enabledComps comp of
-              Nothing -> Left cname
+              Nothing -> Left target'
               Just reason -> Right (cname, reason)
-            | (BuildTargetComponent cname) <- targets
+            | target <- targets
+            , let target'@(cname, _) = swizzleTarget target
             , let comp = getComponent pkg_descr cname
             ]
 
@@ -749,13 +1062,28 @@ checkBuildTargets
       [] -> return ()
       ((cname, reason) : _) -> dieWithException verbosity $ CheckBuildTargets $ formatReason (showComponentName cname) reason
 
+    for_ [(c, t) | (c, Just t) <- enabled] $ \(c, t) ->
+      warn verbosity $
+        "Ignoring '"
+          ++ either prettyShow id t
+          ++ ". The whole "
+          ++ showComponentName c
+          ++ " will be processed. (Support for "
+          ++ "module and file targets has not been implemented yet.)"
+
     -- Pick out the actual CLBIs for each of these cnames
-    for enabled $ \cname -> do
+    enabled' <- for enabled $ \(cname, _) -> do
       case componentNameTargets' pkg_descr lbi cname of
         [] -> error "checkBuildTargets: nothing enabled"
         [target] -> return target
         _targets -> error "checkBuildTargets: multiple copies enabled"
+
+    return enabled'
     where
+      swizzleTarget (BuildTargetComponent c) = (c, Nothing)
+      swizzleTarget (BuildTargetModule c m) = (c, Just (Left m))
+      swizzleTarget (BuildTargetFile c f) = (c, Just (Right f))
+
       formatReason cn DisabledComponent =
         "Cannot process the "
           ++ cn
diff --git a/cabal-install/cabal-install.cabal b/cabal-install/cabal-install.cabal
index 9609262868f..6d22bf3a06a 100644
--- a/cabal-install/cabal-install.cabal
+++ b/cabal-install/cabal-install.cabal
@@ -310,6 +310,7 @@ test-suite unit-tests
       UnitTests.Distribution.Client.InstallPlan
       UnitTests.Distribution.Client.JobControl
       UnitTests.Distribution.Client.ProjectConfig
+      UnitTests.Distribution.Client.ProjectPlanning
       UnitTests.Distribution.Client.Store
       UnitTests.Distribution.Client.Tar
       UnitTests.Distribution.Client.Targets
diff --git a/cabal-install/src/Distribution/Client/CmdBench.hs b/cabal-install/src/Distribution/Client/CmdBench.hs
index db8b50f4b55..b39aa9d6755 100644
--- a/cabal-install/src/Distribution/Client/CmdBench.hs
+++ b/cabal-install/src/Distribution/Client/CmdBench.hs
@@ -8,6 +8,7 @@ module Distribution.Client.CmdBench
 
     -- * Internals exposed for testing
   , componentNotBenchmarkProblem
+  , isSubComponentProblem
   , noBenchmarksProblem
   , selectPackageTargets
   , selectComponentTarget
@@ -196,17 +197,25 @@ selectPackageTargets targetSelector targets
 -- For the @bench@ command we just need to check it is a benchmark, in addition
 -- to the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either BenchTargetProblem k
-selectComponentTarget t
+selectComponentTarget subtarget@WholeComponent t
   | CBenchName _ <- availableTargetComponentName t =
-      selectComponentTargetBasic t
+      selectComponentTargetBasic subtarget t
   | otherwise =
       Left
         ( componentNotBenchmarkProblem
             (availableTargetPackageId t)
             (availableTargetComponentName t)
         )
+selectComponentTarget subtarget t =
+  Left
+    ( isSubComponentProblem
+        (availableTargetPackageId t)
+        (availableTargetComponentName t)
+        subtarget
+    )
 
 -- | The various error conditions that can occur when matching a
 -- 'TargetSelector' against 'AvailableTarget's for the @bench@ command.
@@ -215,6 +224,8 @@ data BenchProblem
     TargetProblemNoBenchmarks TargetSelector
   | -- | The 'TargetSelector' refers to a component that is not a benchmark
     TargetProblemComponentNotBenchmark PackageId ComponentName
+  | -- | Asking to benchmark an individual file or module is not supported
+    TargetProblemIsSubComponent PackageId ComponentName SubComponentTarget
   deriving (Eq, Show)
 
 type BenchTargetProblem = TargetProblem BenchProblem
@@ -227,6 +238,15 @@ componentNotBenchmarkProblem pkgid name =
   CustomTargetProblem $
     TargetProblemComponentNotBenchmark pkgid name
 
+isSubComponentProblem
+  :: PackageId
+  -> ComponentName
+  -> SubComponentTarget
+  -> TargetProblem BenchProblem
+isSubComponentProblem pkgid name subcomponent =
+  CustomTargetProblem $
+    TargetProblemIsSubComponent pkgid name subcomponent
+
 reportTargetProblems :: Verbosity -> [BenchTargetProblem] -> IO a
 reportTargetProblems verbosity =
   dieWithException verbosity . RenderBenchTargetProblem . map renderBenchTargetProblem
@@ -263,4 +283,13 @@ renderBenchProblem (TargetProblemComponentNotBenchmark pkgid cname) =
     ++ prettyShow pkgid
     ++ "."
   where
-    targetSelector = TargetComponent pkgid cname
+    targetSelector = TargetComponent pkgid cname WholeComponent
+renderBenchProblem (TargetProblemIsSubComponent pkgid cname subtarget) =
+  "The bench command can only run benchmarks as a whole, "
+    ++ "not files or modules within them, but the target '"
+    ++ showTargetSelector targetSelector
+    ++ "' refers to "
+    ++ renderTargetSelector targetSelector
+    ++ "."
+  where
+    targetSelector = TargetComponent pkgid cname subtarget
diff --git a/cabal-install/src/Distribution/Client/CmdBuild.hs b/cabal-install/src/Distribution/Client/CmdBuild.hs
index 575e0d95d0b..be4b26b0038 100644
--- a/cabal-install/src/Distribution/Client/CmdBuild.hs
+++ b/cabal-install/src/Distribution/Client/CmdBuild.hs
@@ -226,7 +226,8 @@ selectPackageTargets targetSelector targets
 --
 -- For the @build@ command we just need the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either TargetProblem' k
 selectComponentTarget = selectComponentTargetBasic
 
diff --git a/cabal-install/src/Distribution/Client/CmdErrorMessages.hs b/cabal-install/src/Distribution/Client/CmdErrorMessages.hs
index 0a4b326c9f0..8345d9ed59a 100644
--- a/cabal-install/src/Distribution/Client/CmdErrorMessages.hs
+++ b/cabal-install/src/Distribution/Client/CmdErrorMessages.hs
@@ -24,6 +24,7 @@ import Distribution.Client.TargetProblem
 import Distribution.Client.TargetSelector
   ( ComponentKind (..)
   , ComponentKindFilter
+  , SubComponentTarget (..)
   , TargetSelector (..)
   , componentKind
   , showTargetSelector
@@ -141,18 +142,28 @@ renderTargetSelector (TargetAllPackages (Just kfilter)) =
   "all the "
     ++ renderComponentKind Plural kfilter
     ++ " in the project"
-renderTargetSelector (TargetComponent pkgid cname) =
-  "the "
+renderTargetSelector (TargetComponent pkgid cname subtarget) =
+  renderSubComponentTarget subtarget
+    ++ "the "
     ++ renderComponentName (packageName pkgid) cname
-renderTargetSelector (TargetComponentUnknown pkgname (Left ucname)) =
-  "the component "
+renderTargetSelector (TargetComponentUnknown pkgname (Left ucname) subtarget) =
+  renderSubComponentTarget subtarget
+    ++ "the component "
     ++ prettyShow ucname
     ++ " in the package "
     ++ prettyShow pkgname
-renderTargetSelector (TargetComponentUnknown pkgname (Right cname)) =
-  "the "
+renderTargetSelector (TargetComponentUnknown pkgname (Right cname) subtarget) =
+  renderSubComponentTarget subtarget
+    ++ "the "
     ++ renderComponentName pkgname cname
 
+renderSubComponentTarget :: SubComponentTarget -> String
+renderSubComponentTarget WholeComponent = ""
+renderSubComponentTarget (FileTarget filename) =
+  "the file " ++ filename ++ " in "
+renderSubComponentTarget (ModuleTarget modname) =
+  "the module " ++ prettyShow modname ++ " in "
+
 renderOptionalStanza :: Plural -> OptionalStanza -> String
 renderOptionalStanza Singular TestStanzas = "test suite"
 renderOptionalStanza Plural TestStanzas = "test suites"
@@ -249,7 +260,7 @@ renderTargetProblem verb _ (TargetAvailableInIndex pkgname) =
     ++ "in this project (either directly or indirectly), but it is in the current "
     ++ "package index. If you want to add it to the project then edit the "
     ++ "cabal.project file."
-renderTargetProblem verb _ (TargetComponentNotProjectLocal pkgid cname) =
+renderTargetProblem verb _ (TargetComponentNotProjectLocal pkgid cname _) =
   "Cannot "
     ++ verb
     ++ " the "
@@ -262,7 +273,7 @@ renderTargetProblem verb _ (TargetComponentNotProjectLocal pkgid cname) =
     ++ "non-local dependencies. To run test suites or benchmarks from "
     ++ "dependencies you can unpack the package locally and adjust the "
     ++ "cabal.project file to include that package directory."
-renderTargetProblem verb _ (TargetComponentNotBuildable pkgid cname) =
+renderTargetProblem verb _ (TargetComponentNotBuildable pkgid cname _) =
   "Cannot "
     ++ verb
     ++ " the "
@@ -275,7 +286,7 @@ renderTargetProblem verb _ (TargetComponentNotBuildable pkgid cname) =
     ++ "property is conditional on flags. Alternatively you may simply have to "
     ++ "edit the .cabal file to declare it as buildable and fix any resulting "
     ++ "build problems."
-renderTargetProblem verb _ (TargetOptionalStanzaDisabledByUser _ cname) =
+renderTargetProblem verb _ (TargetOptionalStanzaDisabledByUser _ cname _) =
   "Cannot "
     ++ verb
     ++ " the "
@@ -294,7 +305,7 @@ renderTargetProblem verb _ (TargetOptionalStanzaDisabledByUser _ cname) =
     ++ "explanation."
   where
     compkinds = renderComponentKind Plural (componentKind cname)
-renderTargetProblem verb _ (TargetOptionalStanzaDisabledBySolver pkgid cname) =
+renderTargetProblem verb _ (TargetOptionalStanzaDisabledBySolver pkgid cname _) =
   "Cannot "
     ++ verb
     ++ " the "
diff --git a/cabal-install/src/Distribution/Client/CmdHaddock.hs b/cabal-install/src/Distribution/Client/CmdHaddock.hs
index 0dabb2a745f..b67bda4bcec 100644
--- a/cabal-install/src/Distribution/Client/CmdHaddock.hs
+++ b/cabal-install/src/Distribution/Client/CmdHaddock.hs
@@ -268,7 +268,8 @@ selectPackageTargets haddockFlags targetSelector targets
 -- For the @haddock@ command we just need the basic checks on being buildable
 -- etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either TargetProblem' k
 selectComponentTarget = selectComponentTargetBasic
 
diff --git a/cabal-install/src/Distribution/Client/CmdInstall.hs b/cabal-install/src/Distribution/Client/CmdInstall.hs
index 0adeca99446..4e0a84bda51 100644
--- a/cabal-install/src/Distribution/Client/CmdInstall.hs
+++ b/cabal-install/src/Distribution/Client/CmdInstall.hs
@@ -774,7 +774,7 @@ partitionToKnownTargetsAndHackagePackages verbosity pkgDb elaboratedPlan targetS
 
       let
         targetSelectors' = flip filter targetSelectors $ \case
-          TargetComponentUnknown name _
+          TargetComponentUnknown name _ _
             | name `elem` hackageNames -> False
           TargetPackageNamed name _
             | name `elem` hackageNames -> False
@@ -954,7 +954,7 @@ warnIfNoExes verbosity buildCtx =
     selectors = concatMap (NE.toList . snd) targets
     noExes = null $ catMaybes $ exeMaybe <$> components
 
-    exeMaybe (ComponentTarget (CExeName exe)) = Just exe
+    exeMaybe (ComponentTarget (CExeName exe) _) = Just exe
     exeMaybe _ = Nothing
 
 -- | Return the package specifiers and non-global environment file entries.
@@ -1034,7 +1034,7 @@ installCheckUnitExes
           else traverse_ warnAbout (zip symlinkables exes)
     where
       exes = catMaybes $ (exeMaybe . fst) <$> components
-      exeMaybe (ComponentTarget (CExeName exe)) = Just exe
+      exeMaybe (ComponentTarget (CExeName exe) _) = Just exe
       exeMaybe _ = Nothing
 
       warnAbout (True, _) = return ()
@@ -1136,7 +1136,7 @@ entriesForLibraryComponents :: TargetsMap -> [GhcEnvironmentFileEntry]
 entriesForLibraryComponents = Map.foldrWithKey' (\k v -> mappend (go k v)) []
   where
     hasLib :: (ComponentTarget, NonEmpty TargetSelector) -> Bool
-    hasLib (ComponentTarget (CLibName _), _) = True
+    hasLib (ComponentTarget (CLibName _) _, _) = True
     hasLib _ = False
 
     go
@@ -1262,7 +1262,8 @@ selectPackageTargets targetSelector targets
 --
 -- For the @build@ command we just need the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either TargetProblem' k
 selectComponentTarget = selectComponentTargetBasic
 
diff --git a/cabal-install/src/Distribution/Client/CmdInstall/ClientInstallTargetSelector.hs b/cabal-install/src/Distribution/Client/CmdInstall/ClientInstallTargetSelector.hs
index 2573635f880..c6939729f61 100644
--- a/cabal-install/src/Distribution/Client/CmdInstall/ClientInstallTargetSelector.hs
+++ b/cabal-install/src/Distribution/Client/CmdInstall/ClientInstallTargetSelector.hs
@@ -52,7 +52,7 @@ woPackageTargets :: WithoutProjectTargetSelector -> TargetSelector
 woPackageTargets (WoPackageId pid) =
   TargetPackageNamed (pkgName pid) Nothing
 woPackageTargets (WoPackageComponent pid cn) =
-  TargetComponentUnknown (pkgName pid) (Right cn)
+  TargetComponentUnknown (pkgName pid) (Right cn) WholeComponent
 woPackageTargets (WoURI _) =
   TargetAllPackages (Just ExeKind)
 
diff --git a/cabal-install/src/Distribution/Client/CmdListBin.hs b/cabal-install/src/Distribution/Client/CmdListBin.hs
index 6c4c112c44d..1fefd3a7375 100644
--- a/cabal-install/src/Distribution/Client/CmdListBin.hs
+++ b/cabal-install/src/Distribution/Client/CmdListBin.hs
@@ -290,9 +290,10 @@ selectPackageTargets targetSelector targets
 -- (an executable, a test, or a benchmark), in addition
 -- to the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either ListBinTargetProblem k
-selectComponentTarget t =
+selectComponentTarget subtarget@WholeComponent t =
   case availableTargetComponentName t of
     CExeName _ -> component
     CTestName _ -> component
@@ -302,7 +303,14 @@ selectComponentTarget t =
   where
     pkgid = availableTargetPackageId t
     cname = availableTargetComponentName t
-    component = selectComponentTargetBasic t
+    component = selectComponentTargetBasic subtarget t
+selectComponentTarget subtarget t =
+  Left
+    ( isSubComponentProblem
+        (availableTargetPackageId t)
+        (availableTargetComponentName t)
+        subtarget
+    )
 
 -- | The various error conditions that can occur when matching a
 -- 'TargetSelector' against 'AvailableTarget's for the @run@ command.
@@ -315,6 +323,8 @@ data ListBinProblem
     TargetProblemMultipleTargets TargetsMap
   | -- | The 'TargetSelector' refers to a component that is not an executable
     TargetProblemComponentNotRightKind PackageId ComponentName
+  | -- | Asking to run an individual file or module is not supported
+    TargetProblemIsSubComponent PackageId ComponentName SubComponentTarget
   deriving (Eq, Show)
 
 type ListBinTargetProblem = TargetProblem ListBinProblem
@@ -335,6 +345,15 @@ componentNotRightKindProblem pkgid name =
   CustomTargetProblem $
     TargetProblemComponentNotRightKind pkgid name
 
+isSubComponentProblem
+  :: PackageId
+  -> ComponentName
+  -> SubComponentTarget
+  -> TargetProblem ListBinProblem
+isSubComponentProblem pkgid name subcomponent =
+  CustomTargetProblem $
+    TargetProblemIsSubComponent pkgid name subcomponent
+
 reportTargetProblems :: Verbosity -> [ListBinTargetProblem] -> IO a
 reportTargetProblems verbosity =
   dieWithException verbosity . ListBinTargetException . unlines . map renderListBinTargetProblem
@@ -385,7 +404,16 @@ renderListBinProblem (TargetProblemComponentNotRightKind pkgid cname) =
     ++ prettyShow pkgid
     ++ "."
   where
-    targetSelector = TargetComponent pkgid cname
+    targetSelector = TargetComponent pkgid cname WholeComponent
+renderListBinProblem (TargetProblemIsSubComponent pkgid cname subtarget) =
+  "The list-bin command can only find a binary as a whole, "
+    ++ "not files or modules within them, but the target '"
+    ++ showTargetSelector targetSelector
+    ++ "' refers to "
+    ++ renderTargetSelector targetSelector
+    ++ "."
+  where
+    targetSelector = TargetComponent pkgid cname subtarget
 renderListBinProblem (TargetProblemNoRightComps targetSelector) =
   "Cannot list-bin the target '"
     ++ showTargetSelector targetSelector
diff --git a/cabal-install/src/Distribution/Client/CmdRepl.hs b/cabal-install/src/Distribution/Client/CmdRepl.hs
index bed2cdc6ee8..e243eb82974 100644
--- a/cabal-install/src/Distribution/Client/CmdRepl.hs
+++ b/cabal-install/src/Distribution/Client/CmdRepl.hs
@@ -734,7 +734,8 @@ selectPackageTargetsSingle decision targetSelector targets
 --
 -- For the @repl@ command we just need the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either ReplTargetProblem k
 selectComponentTarget = selectComponentTargetBasic
 
diff --git a/cabal-install/src/Distribution/Client/CmdRun.hs b/cabal-install/src/Distribution/Client/CmdRun.hs
index a2a9cebd637..b390dacb22e 100644
--- a/cabal-install/src/Distribution/Client/CmdRun.hs
+++ b/cabal-install/src/Distribution/Client/CmdRun.hs
@@ -439,9 +439,10 @@ selectPackageTargets targetSelector targets
 -- (an executable, a test, or a benchmark), in addition
 -- to the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either RunTargetProblem k
-selectComponentTarget t =
+selectComponentTarget subtarget@WholeComponent t =
   case availableTargetComponentName t of
     CExeName _ -> component
     CTestName _ -> component
@@ -450,7 +451,14 @@ selectComponentTarget t =
   where
     pkgid = availableTargetPackageId t
     cname = availableTargetComponentName t
-    component = selectComponentTargetBasic t
+    component = selectComponentTargetBasic subtarget t
+selectComponentTarget subtarget t =
+  Left
+    ( isSubComponentProblem
+        (availableTargetPackageId t)
+        (availableTargetComponentName t)
+        subtarget
+    )
 
 -- | The various error conditions that can occur when matching a
 -- 'TargetSelector' against 'AvailableTarget's for the @run@ command.
@@ -463,6 +471,8 @@ data RunProblem
     TargetProblemMultipleTargets TargetsMap
   | -- | The 'TargetSelector' refers to a component that is not an executable
     TargetProblemComponentNotExe PackageId ComponentName
+  | -- | Asking to run an individual file or module is not supported
+    TargetProblemIsSubComponent PackageId ComponentName SubComponentTarget
   deriving (Eq, Show)
 
 type RunTargetProblem = TargetProblem RunProblem
@@ -483,6 +493,15 @@ componentNotExeProblem pkgid name =
   CustomTargetProblem $
     TargetProblemComponentNotExe pkgid name
 
+isSubComponentProblem
+  :: PackageId
+  -> ComponentName
+  -> SubComponentTarget
+  -> TargetProblem RunProblem
+isSubComponentProblem pkgid name subcomponent =
+  CustomTargetProblem $
+    TargetProblemIsSubComponent pkgid name subcomponent
+
 reportTargetProblems :: Verbosity -> [RunTargetProblem] -> IO a
 reportTargetProblems verbosity =
   dieWithException verbosity . CmdRunReportTargetProblems . unlines . map renderRunTargetProblem
@@ -536,7 +555,16 @@ renderRunProblem (TargetProblemComponentNotExe pkgid cname) =
     ++ prettyShow pkgid
     ++ "."
   where
-    targetSelector = TargetComponent pkgid cname
+    targetSelector = TargetComponent pkgid cname WholeComponent
+renderRunProblem (TargetProblemIsSubComponent pkgid cname subtarget) =
+  "The run command can only run an executable as a whole, "
+    ++ "not files or modules within them, but the target '"
+    ++ showTargetSelector targetSelector
+    ++ "' refers to "
+    ++ renderTargetSelector targetSelector
+    ++ "."
+  where
+    targetSelector = TargetComponent pkgid cname subtarget
 renderRunProblem (TargetProblemNoExes targetSelector) =
   "Cannot run the target '"
     ++ showTargetSelector targetSelector
diff --git a/cabal-install/src/Distribution/Client/CmdSdist.hs b/cabal-install/src/Distribution/Client/CmdSdist.hs
index 01ab558e655..c77c1eae910 100644
--- a/cabal-install/src/Distribution/Client/CmdSdist.hs
+++ b/cabal-install/src/Distribution/Client/CmdSdist.hs
@@ -377,8 +377,8 @@ reifyTargetSelectors pkgs sels =
     go (TargetPackage _ _ (Just kind)) = [Left (AllComponentsOnly kind)]
     go (TargetAllPackages (Just kind)) = [Left (AllComponentsOnly kind)]
     go (TargetPackageNamed pname _) = [Left (NonlocalPackageNotAllowed pname)]
-    go (TargetComponentUnknown pname _) = [Left (NonlocalPackageNotAllowed pname)]
-    go (TargetComponent _ cname) = [Left (ComponentsNotAllowed cname)]
+    go (TargetComponentUnknown pname _ _) = [Left (NonlocalPackageNotAllowed pname)]
+    go (TargetComponent _ cname _) = [Left (ComponentsNotAllowed cname)]
 
 data TargetProblem
   = AllComponentsOnly ComponentKind
diff --git a/cabal-install/src/Distribution/Client/CmdTest.hs b/cabal-install/src/Distribution/Client/CmdTest.hs
index bb5ed9d124f..74fcc3a78b2 100644
--- a/cabal-install/src/Distribution/Client/CmdTest.hs
+++ b/cabal-install/src/Distribution/Client/CmdTest.hs
@@ -7,6 +7,7 @@ module Distribution.Client.CmdTest
   , testAction
 
     -- * Internals exposed for testing
+  , isSubComponentProblem
   , notTestProblem
   , noTestsProblem
   , selectPackageTargets
@@ -205,18 +206,26 @@ selectPackageTargets targetSelector targets
 -- For the @test@ command we just need to check it is a test-suite, in addition
 -- to the basic checks on being buildable etc.
 selectComponentTarget
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either TestTargetProblem k
-selectComponentTarget t
+selectComponentTarget subtarget@WholeComponent t
   | CTestName _ <- availableTargetComponentName t =
       either Left return $
-        selectComponentTargetBasic t
+        selectComponentTargetBasic subtarget t
   | otherwise =
       Left
         ( notTestProblem
             (availableTargetPackageId t)
             (availableTargetComponentName t)
         )
+selectComponentTarget subtarget t =
+  Left
+    ( isSubComponentProblem
+        (availableTargetPackageId t)
+        (availableTargetComponentName t)
+        subtarget
+    )
 
 -- | The various error conditions that can occur when matching a
 -- 'TargetSelector' against 'AvailableTarget's for the @test@ command.
@@ -225,6 +234,8 @@ data TestProblem
     TargetProblemNoTests TargetSelector
   | -- | The 'TargetSelector' refers to a component that is not a test-suite
     TargetProblemComponentNotTest PackageId ComponentName
+  | -- | Asking to test an individual file or module is not supported
+    TargetProblemIsSubComponent PackageId ComponentName SubComponentTarget
   deriving (Eq, Show)
 
 type TestTargetProblem = TargetProblem TestProblem
@@ -235,6 +246,15 @@ noTestsProblem = CustomTargetProblem . TargetProblemNoTests
 notTestProblem :: PackageId -> ComponentName -> TargetProblem TestProblem
 notTestProblem pkgid name = CustomTargetProblem $ TargetProblemComponentNotTest pkgid name
 
+isSubComponentProblem
+  :: PackageId
+  -> ComponentName
+  -> SubComponentTarget
+  -> TargetProblem TestProblem
+isSubComponentProblem pkgid name subcomponent =
+  CustomTargetProblem $
+    TargetProblemIsSubComponent pkgid name subcomponent
+
 reportTargetProblems :: Verbosity -> Flag Bool -> [TestTargetProblem] -> IO a
 reportTargetProblems verbosity failWhenNoTestSuites problems =
   case (failWhenNoTestSuites, problems) of
@@ -289,4 +309,13 @@ renderTestProblem (TargetProblemComponentNotTest pkgid cname) =
     ++ prettyShow pkgid
     ++ "."
   where
-    targetSelector = TargetComponent pkgid cname
+    targetSelector = TargetComponent pkgid cname WholeComponent
+renderTestProblem (TargetProblemIsSubComponent pkgid cname subtarget) =
+  "The test command can only run test suites as a whole, "
+    ++ "not files or modules within them, but the target '"
+    ++ showTargetSelector targetSelector
+    ++ "' refers to "
+    ++ renderTargetSelector targetSelector
+    ++ "."
+  where
+    targetSelector = TargetComponent pkgid cname subtarget
diff --git a/cabal-install/src/Distribution/Client/ProjectBuilding/PackageFileMonitor.hs b/cabal-install/src/Distribution/Client/ProjectBuilding/PackageFileMonitor.hs
index eef99b280c3..b93064ea7be 100644
--- a/cabal-install/src/Distribution/Client/ProjectBuilding/PackageFileMonitor.hs
+++ b/cabal-install/src/Distribution/Client/ProjectBuilding/PackageFileMonitor.hs
@@ -92,20 +92,19 @@ packageFileMonitorKeyValues
 packageFileMonitorKeyValues elab =
   (elab_config, buildComponents)
   where
-    -- The first part, 'elab_config', is the value used to guard (re)configuring the package.
+    -- The first part is the value used to guard (re)configuring the package.
     -- That is, if this value changes then we will reconfigure.
     -- The ElaboratedConfiguredPackage consists mostly (but not entirely) of
     -- information that affects the (re)configure step. But those parts that
     -- do not affect the configure step need to be nulled out. Those parts are
     -- the specific targets that we're going to build.
     --
-    -- The second part is the value used to guard the build step. So this is
-    -- more or less the opposite of the first part, as it's just the info about
-    -- what targets we're going to build.
-    --
+
     -- Additionally we null out the parts that don't affect the configure step because they're simply
     -- about how tests or benchmarks are run
 
+    -- TODO there may be more things to null here too, in the future.
+
     elab_config :: ElaboratedConfiguredPackage
     elab_config =
       elab
@@ -128,7 +127,7 @@ packageFileMonitorKeyValues elab =
     -- what targets we're going to build.
     --
     buildComponents :: Set ComponentName
-    buildComponents = Set.fromList [cn | ComponentTarget cn <- elabBuildTargets elab]
+    buildComponents = elabBuildTargetWholeComponents elab
 
 -- | Do all the checks on whether a package has changed and thus needs either
 -- rebuilding or reconfiguring and rebuilding.
diff --git a/cabal-install/src/Distribution/Client/ProjectBuilding/UnpackedPackage.hs b/cabal-install/src/Distribution/Client/ProjectBuilding/UnpackedPackage.hs
index 0a95df746af..cbe5a67cea6 100644
--- a/cabal-install/src/Distribution/Client/ProjectBuilding/UnpackedPackage.hs
+++ b/cabal-install/src/Distribution/Client/ProjectBuilding/UnpackedPackage.hs
@@ -887,7 +887,7 @@ hasValidHaddockTargets ElaboratedConfiguredPackage{..}
         ++ elabHaddockTargets
 
     componentHasHaddocks :: ComponentTarget -> Bool
-    componentHasHaddocks (ComponentTarget name) =
+    componentHasHaddocks (ComponentTarget name _) =
       case name of
         CLibName LMainLibName -> hasHaddocks
         CLibName (LSubLibName _) -> elabHaddockInternal && hasHaddocks
diff --git a/cabal-install/src/Distribution/Client/ProjectOrchestration.hs b/cabal-install/src/Distribution/Client/ProjectOrchestration.hs
index 4f5c9faeed8..db99b2576b9 100644
--- a/cabal-install/src/Distribution/Client/ProjectOrchestration.hs
+++ b/cabal-install/src/Distribution/Client/ProjectOrchestration.hs
@@ -71,6 +71,7 @@ module Distribution.Client.ProjectOrchestration
   , ComponentName (..)
   , ComponentKind (..)
   , ComponentTarget (..)
+  , SubComponentTarget (..)
   , selectComponentTargetBasic
   , distinctTargetComponents
 
@@ -607,7 +608,8 @@ resolveTargets
        -> Either (TargetProblem err) [k]
      )
   -> ( forall k
-        . AvailableTarget k
+        . SubComponentTarget
+       -> AvailableTarget k
        -> Either (TargetProblem err) k
      )
   -> ElaboratedInstallPlan
@@ -645,7 +647,7 @@ resolveTargets
         | Just ats <-
             fmap (maybe id filterTargetsKind mkfilter) $
               Map.lookup pkgid availableTargetsByPackageId =
-            fmap componentTargets $
+            fmap (componentTargets WholeComponent) $
               selectPackageTargets bt ats
         | otherwise =
             Left (TargetProblemNoSuchPackage pkgid)
@@ -663,23 +665,23 @@ resolveTargets
       -- .cabal files for a single package?
 
       checkTarget bt@(TargetAllPackages mkfilter) =
-        fmap componentTargets
+        fmap (componentTargets WholeComponent)
           . selectPackageTargets bt
           . maybe id filterTargetsKind mkfilter
           . filter availableTargetLocalToProject
           $ concat (Map.elems availableTargetsByPackageId)
-      checkTarget (TargetComponent pkgid cname)
+      checkTarget (TargetComponent pkgid cname subtarget)
         | Just ats <-
             Map.lookup
               (pkgid, cname)
               availableTargetsByPackageIdAndComponentName =
-            fmap componentTargets $
-              selectComponentTargets ats
+            fmap (componentTargets subtarget) $
+              selectComponentTargets subtarget ats
         | Map.member pkgid availableTargetsByPackageId =
             Left (TargetProblemNoSuchComponent pkgid cname)
         | otherwise =
             Left (TargetProblemNoSuchPackage pkgid)
-      checkTarget (TargetComponentUnknown pkgname ecname)
+      checkTarget (TargetComponentUnknown pkgname ecname subtarget)
         | Just ats <- case ecname of
             Left ucname ->
               Map.lookup
@@ -689,8 +691,8 @@ resolveTargets
               Map.lookup
                 (pkgname, cname)
                 availableTargetsByPackageNameAndComponentName =
-            fmap componentTargets $
-              selectComponentTargets ats
+            fmap (componentTargets subtarget) $
+              selectComponentTargets subtarget ats
         | Map.member pkgname availableTargetsByPackageName =
             Left (TargetProblemUnknownComponent pkgname ecname)
         | otherwise =
@@ -699,7 +701,7 @@ resolveTargets
         | Just ats <-
             fmap (maybe id filterTargetsKind mkfilter) $
               Map.lookup pkgname availableTargetsByPackageName =
-            fmap componentTargets
+            fmap (componentTargets WholeComponent)
               . selectPackageTargets bt
               $ ats
         | Just SourcePackageDb{packageIndex} <- mPkgDb
@@ -710,18 +712,20 @@ resolveTargets
             Left (TargetNotInProject pkgname)
 
       componentTargets
-        :: [(b, ComponentName)]
+        :: SubComponentTarget
+        -> [(b, ComponentName)]
         -> [(b, ComponentTarget)]
-      componentTargets =
-        map (fmap (\cname -> ComponentTarget cname))
+      componentTargets subtarget =
+        map (fmap (\cname -> ComponentTarget cname subtarget))
 
       selectComponentTargets
-        :: [AvailableTarget k]
+        :: SubComponentTarget
+        -> [AvailableTarget k]
         -> Either (TargetProblem err) [k]
-      selectComponentTargets =
+      selectComponentTargets subtarget =
         either (Left . NE.head) Right
           . checkErrors
-          . map selectComponentTarget
+          . map (selectComponentTarget subtarget)
 
       checkErrors :: [Either e a] -> Either (NonEmpty e) [a]
       checkErrors =
@@ -877,9 +881,11 @@ forgetTargetsDetail = map forgetTargetDetail
 -- buildable and isn't a test suite or benchmark that is disabled. This
 -- can also be used to do these basic checks as part of a custom impl that
 selectComponentTargetBasic
-  :: AvailableTarget k
+  :: SubComponentTarget
+  -> AvailableTarget k
   -> Either (TargetProblem a) k
 selectComponentTargetBasic
+  subtarget
   AvailableTarget
     { availableTargetPackageId = pkgid
     , availableTargetComponentName = cname
@@ -887,13 +893,13 @@ selectComponentTargetBasic
     } =
     case availableTargetStatus of
       TargetDisabledByUser ->
-        Left (TargetOptionalStanzaDisabledByUser pkgid cname)
+        Left (TargetOptionalStanzaDisabledByUser pkgid cname subtarget)
       TargetDisabledBySolver ->
-        Left (TargetOptionalStanzaDisabledBySolver pkgid cname)
+        Left (TargetOptionalStanzaDisabledBySolver pkgid cname subtarget)
       TargetNotLocal ->
-        Left (TargetComponentNotProjectLocal pkgid cname)
+        Left (TargetComponentNotProjectLocal pkgid cname subtarget)
       TargetNotBuildable ->
-        Left (TargetComponentNotBuildable pkgid cname)
+        Left (TargetComponentNotBuildable pkgid cname subtarget)
       TargetBuildable targetKey _ ->
         Right targetKey
 
@@ -918,7 +924,7 @@ distinctTargetComponents targetsMap =
   Set.fromList
     [ (uid, cname)
     | (uid, cts) <- Map.toList targetsMap
-    , (ComponentTarget cname, _) <- cts
+    , (ComponentTarget cname _, _) <- cts
     ]
 
 ------------------------------------------------------------------------------
diff --git a/cabal-install/src/Distribution/Client/ProjectPlanning.hs b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
index deff1f38bf0..ad9e507ae5c 100644
--- a/cabal-install/src/Distribution/Client/ProjectPlanning.hs
+++ b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
@@ -57,6 +57,7 @@ module Distribution.Client.ProjectPlanning
   , AvailableTargetStatus (..)
   , TargetRequested (..)
   , ComponentTarget (..)
+  , SubComponentTarget (..)
   , showComponentTarget
   , nubComponentTargets
 
@@ -68,6 +69,7 @@ module Distribution.Client.ProjectPlanning
 
     -- * Utils required for building
   , pkgHasEphemeralBuildTargets
+  , elabBuildTargetWholeComponents
   , configureCompiler
 
     -- * Setup.hs CLI flags for building
@@ -3051,7 +3053,7 @@ nubComponentTargets =
   concatMap (wholeComponentOverrides . map snd)
     . groupBy ((==) `on` fst)
     . sortBy (compare `on` fst)
-    . map (\t@((ComponentTarget cname, _)) -> (cname, t))
+    . map (\t@((ComponentTarget cname _, _)) -> (cname, t))
     . map compatSubComponentTargets
   where
     -- If we're building the whole component then that the only target all we
@@ -3060,7 +3062,7 @@ nubComponentTargets =
       :: [(ComponentTarget, a)]
       -> [(ComponentTarget, NonEmpty a)]
     wholeComponentOverrides ts =
-      case [ta | ta@(ComponentTarget _, _) <- ts] of
+      case [ta | ta@(ComponentTarget _ WholeComponent, _) <- ts] of
         ((t, x) : _) ->
           let
             -- Delete tuple (t, x) from original list to avoid duplicates.
@@ -3073,9 +3075,9 @@ nubComponentTargets =
     -- Not all Cabal Setup.hs versions support sub-component targets, so switch
     -- them over to the whole component
     compatSubComponentTargets :: (ComponentTarget, a) -> (ComponentTarget, a)
-    compatSubComponentTargets target@(ComponentTarget cname, x)
+    compatSubComponentTargets target@(ComponentTarget cname _subtarget, x)
       | not setupHsSupportsSubComponentTargets =
-          (ComponentTarget cname, x)
+          (ComponentTarget cname WholeComponent, x)
       | otherwise = target
 
     -- Actually the reality is that no current version of Cabal's Setup.hs
@@ -3091,6 +3093,19 @@ pkgHasEphemeralBuildTargets elab =
     || (not . null) (elabTestTargets elab)
     || (not . null) (elabBenchTargets elab)
     || (not . null) (elabHaddockTargets elab)
+    || (not . null)
+      [ () | ComponentTarget _ subtarget <- elabBuildTargets elab, subtarget /= WholeComponent
+      ]
+
+-- | The components that we'll build all of, meaning that after they're built
+-- we can skip building them again (unlike with building just some modules or
+-- other files within a component).
+elabBuildTargetWholeComponents
+  :: ElaboratedConfiguredPackage
+  -> Set ComponentName
+elabBuildTargetWholeComponents elab =
+  Set.fromList
+    [cname | ComponentTarget cname WholeComponent <- elabBuildTargets elab]
 
 ------------------------------------------------------------------------------
 
@@ -3264,7 +3279,7 @@ pruneInstallPlanPass1 pkgs
     add_repl_target ecp
       | elabUnitId ecp `Set.member` all_desired_repl_targets =
           ecp
-            { elabReplTarget = maybeToList (ComponentTarget <$> elabComponentName ecp)
+            { elabReplTarget = maybeToList (ComponentTarget <$> (elabComponentName ecp) <*> pure WholeComponent)
             , elabBuildStyle = BuildInplaceOnly InMemory
             }
       | otherwise = ecp
@@ -3402,7 +3417,7 @@ pruneInstallPlanPass1 pkgs
     optionalStanzasRequiredByTargets pkg =
       optStanzaSetFromList
         [ stanza
-        | ComponentTarget cname <-
+        | ComponentTarget cname _ <-
             elabBuildTargets pkg
               ++ elabTestTargets pkg
               ++ elabBenchTargets pkg
@@ -3562,7 +3577,7 @@ pruneInstallPlanPass2 pkgs =
         libTargetsRequiredForRevDeps =
           [ c
           | installedUnitId elab `Set.member` hasReverseLibDeps
-          , let c = ComponentTarget (CLibName Cabal.defaultLibName)
+          , let c = ComponentTarget (CLibName Cabal.defaultLibName) WholeComponent
           , -- Don't enable building for anything which is being build in memory
           elabBuildStyle elab /= BuildInplaceOnly InMemory
           ]
@@ -3575,6 +3590,7 @@ pruneInstallPlanPass2 pkgs =
                   packageName $
                     elabPkgSourceId elab
             )
+            WholeComponent
           | installedUnitId elab `Set.member` hasReverseExeDeps
           ]
 
@@ -3990,7 +4006,7 @@ setupHsConfigureArgs
   -> [String]
 setupHsConfigureArgs (ElaboratedConfiguredPackage{elabPkgOrComp = ElabPackage _}) = []
 setupHsConfigureArgs elab@(ElaboratedConfiguredPackage{elabPkgOrComp = ElabComponent comp}) =
-  [showComponentTarget (packageId elab) (ComponentTarget cname)]
+  [showComponentTarget (packageId elab) (ComponentTarget cname WholeComponent)]
   where
     cname =
       fromMaybe
diff --git a/cabal-install/src/Distribution/Client/ProjectPlanning/Types.hs b/cabal-install/src/Distribution/Client/ProjectPlanning/Types.hs
index 1a5ace436ae..96de8adea45 100644
--- a/cabal-install/src/Distribution/Client/ProjectPlanning/Types.hs
+++ b/cabal-install/src/Distribution/Client/ProjectPlanning/Types.hs
@@ -48,6 +48,7 @@ module Distribution.Client.ProjectPlanning.Types
   , showComponentTarget
   , showTestComponentTarget
   , showBenchComponentTarget
+  , SubComponentTarget (..)
   , isSubLibComponentTarget
   , isForeignLibComponentTarget
   , isExeComponentTarget
@@ -63,6 +64,9 @@ import Distribution.Client.Compat.Prelude
 import Prelude ()
 
 import Distribution.Client.PackageHash
+import Distribution.Client.TargetSelector
+  ( SubComponentTarget (..)
+  )
 
 import Distribution.Client.DistDirLayout
 import Distribution.Client.InstallPlan
@@ -393,7 +397,7 @@ elabRequiresRegistration elab =
         -- redundant anymore.
         || any (depends_on_lib pkg) (elabBuildTargets elab)
   where
-    depends_on_lib pkg (ComponentTarget cn) =
+    depends_on_lib pkg (ComponentTarget cn _) =
       not
         ( null
             ( CD.select
@@ -408,11 +412,10 @@ elabRequiresRegistration elab =
         -- that means we have to look more carefully to see
         -- if there is anything to register
           Cabal.hasLibs (elabPkgDescription elab)
-
     -- NB: this means we DO NOT reregister if you just built a
     -- single file
-    is_lib_target (ComponentTarget cn) = is_lib cn
-
+    is_lib_target (ComponentTarget cn WholeComponent) = is_lib cn
+    is_lib_target _ = False
     is_lib (CLibName _) = True
     is_lib _ = False
 
@@ -797,7 +800,7 @@ type ElaboratedReadyPackage = GenericReadyPackage ElaboratedConfiguredPackage
 
 -- | Specific targets within a package or component to act on e.g. to build,
 -- haddock or open a repl.
-data ComponentTarget = ComponentTarget ComponentName
+data ComponentTarget = ComponentTarget ComponentName SubComponentTarget
   deriving (Eq, Ord, Show, Generic)
 
 instance Binary ComponentTarget
@@ -810,35 +813,38 @@ showComponentTarget pkgid =
   Cabal.showBuildTarget pkgid . toBuildTarget
   where
     toBuildTarget :: ComponentTarget -> Cabal.BuildTarget
-    toBuildTarget (ComponentTarget cname) =
-      Cabal.BuildTargetComponent cname
+    toBuildTarget (ComponentTarget cname subtarget) =
+      case subtarget of
+        WholeComponent -> Cabal.BuildTargetComponent cname
+        ModuleTarget mname -> Cabal.BuildTargetModule cname mname
+        FileTarget fname -> Cabal.BuildTargetFile cname fname
 
 showTestComponentTarget :: PackageId -> ComponentTarget -> Maybe String
-showTestComponentTarget _ (ComponentTarget (CTestName n)) = Just $ prettyShow n
+showTestComponentTarget _ (ComponentTarget (CTestName n) _) = Just $ prettyShow n
 showTestComponentTarget _ _ = Nothing
 
 isTestComponentTarget :: ComponentTarget -> Bool
-isTestComponentTarget (ComponentTarget (CTestName _)) = True
+isTestComponentTarget (ComponentTarget (CTestName _) _) = True
 isTestComponentTarget _ = False
 
 showBenchComponentTarget :: PackageId -> ComponentTarget -> Maybe String
-showBenchComponentTarget _ (ComponentTarget (CBenchName n)) = Just $ prettyShow n
+showBenchComponentTarget _ (ComponentTarget (CBenchName n) _) = Just $ prettyShow n
 showBenchComponentTarget _ _ = Nothing
 
 isBenchComponentTarget :: ComponentTarget -> Bool
-isBenchComponentTarget (ComponentTarget (CBenchName _)) = True
+isBenchComponentTarget (ComponentTarget (CBenchName _) _) = True
 isBenchComponentTarget _ = False
 
 isForeignLibComponentTarget :: ComponentTarget -> Bool
-isForeignLibComponentTarget (ComponentTarget (CFLibName _)) = True
+isForeignLibComponentTarget (ComponentTarget (CFLibName _) _) = True
 isForeignLibComponentTarget _ = False
 
 isExeComponentTarget :: ComponentTarget -> Bool
-isExeComponentTarget (ComponentTarget (CExeName _)) = True
+isExeComponentTarget (ComponentTarget (CExeName _) _) = True
 isExeComponentTarget _ = False
 
 isSubLibComponentTarget :: ComponentTarget -> Bool
-isSubLibComponentTarget (ComponentTarget (CLibName (LSubLibName _))) = True
+isSubLibComponentTarget (ComponentTarget (CLibName (LSubLibName _)) _) = True
 isSubLibComponentTarget _ = False
 
 componentOptionalStanza :: CD.Component -> Maybe OptionalStanza
diff --git a/cabal-install/src/Distribution/Client/TargetProblem.hs b/cabal-install/src/Distribution/Client/TargetProblem.hs
index 1292c490968..680250273c0 100644
--- a/cabal-install/src/Distribution/Client/TargetProblem.hs
+++ b/cabal-install/src/Distribution/Client/TargetProblem.hs
@@ -9,7 +9,7 @@ import Distribution.Client.Compat.Prelude
 import Prelude ()
 
 import Distribution.Client.ProjectPlanning (AvailableTarget)
-import Distribution.Client.TargetSelector (TargetSelector)
+import Distribution.Client.TargetSelector (SubComponentTarget, TargetSelector)
 import Distribution.Package (PackageId, PackageName)
 import Distribution.Simple.LocalBuildInfo (ComponentName (..))
 import Distribution.Types.UnqualComponentName (UnqualComponentName)
@@ -21,15 +21,19 @@ data TargetProblem a
   | TargetComponentNotProjectLocal
       PackageId
       ComponentName
+      SubComponentTarget
   | TargetComponentNotBuildable
       PackageId
       ComponentName
+      SubComponentTarget
   | TargetOptionalStanzaDisabledByUser
       PackageId
       ComponentName
+      SubComponentTarget
   | TargetOptionalStanzaDisabledBySolver
       PackageId
       ComponentName
+      SubComponentTarget
   | TargetProblemUnknownComponent
       PackageName
       (Either UnqualComponentName ComponentName)
diff --git a/cabal-install/src/Distribution/Client/TargetSelector.hs b/cabal-install/src/Distribution/Client/TargetSelector.hs
index 4932f07361f..d29413642de 100644
--- a/cabal-install/src/Distribution/Client/TargetSelector.hs
+++ b/cabal-install/src/Distribution/Client/TargetSelector.hs
@@ -25,6 +25,7 @@ module Distribution.Client.TargetSelector
   , TargetImplicitCwd (..)
   , ComponentKind (..)
   , ComponentKindFilter
+  , SubComponentTarget (..)
   , QualLevel (..)
   , componentKind
 
@@ -65,6 +66,7 @@ import Distribution.Types.UnqualComponentName
 
 import Distribution.ModuleName
   ( ModuleName
+  , toFilePath
   )
 import Distribution.PackageDescription
   ( Benchmark (..)
@@ -99,6 +101,9 @@ import Control.Arrow ((&&&))
 import Control.Monad hiding
   ( mfilter
   )
+import Data.List
+  ( stripPrefix
+  )
 import qualified Data.List.NonEmpty as NE
 import qualified Data.Map.Lazy as Map.Lazy
 import qualified Data.Map.Strict as Map
@@ -130,11 +135,15 @@ import qualified System.Directory as IO
 import System.FilePath
   ( dropTrailingPathSeparator
   , equalFilePath
+  , normalise
   , (<.>)
   , (</>)
   )
 import System.FilePath as FilePath
-  ( splitPath
+  ( dropExtension
+  , joinPath
+  , splitDirectories
+  , splitPath
   , takeExtension
   )
 import Text.EditDistance
@@ -183,13 +192,14 @@ data TargetSelector
   | -- | All packages, or all components of a particular kind in all packages.
     TargetAllPackages (Maybe ComponentKindFilter)
   | -- | A specific component in a package within the project.
-    TargetComponent PackageId ComponentName
+    TargetComponent PackageId ComponentName SubComponentTarget
   | -- | A component in a package, but where it cannot be verified that the
     -- package has such a component, or because the package is itself not
     -- known.
     TargetComponentUnknown
       PackageName
       (Either UnqualComponentName ComponentName)
+      SubComponentTarget
   deriving (Eq, Ord, Show, Generic)
 
 -- | Does this 'TargetPackage' selector arise from syntax referring to a
@@ -204,6 +214,21 @@ data ComponentKind = LibKind | FLibKind | ExeKind | TestKind | BenchKind
 
 type ComponentKindFilter = ComponentKind
 
+-- | Either the component as a whole or detail about a file or module target
+-- within a component.
+data SubComponentTarget
+  = -- | The component as a whole
+    WholeComponent
+  | -- | A specific module within a component.
+    ModuleTarget ModuleName
+  | -- | A specific file within a component. Note that this does not carry the
+    -- file extension.
+    FileTarget FilePath
+  deriving (Eq, Ord, Show, Generic)
+
+instance Binary SubComponentTarget
+instance Structured SubComponentTarget
+
 -- ------------------------------------------------------------
 
 -- * Top level, do everything
@@ -389,8 +414,12 @@ showTargetSelectorKind bt = case bt of
   TargetPackageNamed _ (Just _) -> "named-package:filter"
   TargetAllPackages Nothing -> "package *"
   TargetAllPackages (Just _) -> "package *:filter"
-  TargetComponent _ _ -> "component"
-  TargetComponentUnknown _ _ -> "unknown-component"
+  TargetComponent _ _ WholeComponent -> "component"
+  TargetComponent _ _ ModuleTarget{} -> "module"
+  TargetComponent _ _ FileTarget{} -> "file"
+  TargetComponentUnknown _ _ WholeComponent -> "unknown-component"
+  TargetComponentUnknown _ _ ModuleTarget{} -> "unknown-module"
+  TargetComponentUnknown _ _ FileTarget{} -> "unknown-file"
 
 -- ------------------------------------------------------------
 
@@ -607,7 +636,7 @@ resolveTargetSelector knowntargets@KnownTargets{..} mfilter targetStrStatus =
         go (TargetPackage _ _ (Just filter')) = kfilter == filter'
         go (TargetPackageNamed _ (Just filter')) = kfilter == filter'
         go (TargetAllPackages (Just filter')) = kfilter == filter'
-        go (TargetComponent _ cname)
+        go (TargetComponent _ cname _)
           | CLibName _ <- cname = kfilter == LibKind
           | CFLibName _ <- cname = kfilter == FLibKind
           | CExeName _ <- cname = kfilter == ExeKind
@@ -936,6 +965,8 @@ syntaxForms
                   ]
               ]
           , syntaxForm1Component ocinfo
+          , syntaxForm1Module cinfo
+          , syntaxForm1File pinfo
           ]
       , -- two-component partially qualified forms
         -- fully qualified form for 'all'
@@ -945,8 +976,24 @@ syntaxForms
       , syntaxForm2PackageComponent pinfo
       , syntaxForm2PackageFilter pinfo
       , syntaxForm2KindComponent cinfo
+      , shadowingAlternatives
+          [ syntaxForm2PackageModule pinfo
+          , syntaxForm2PackageFile pinfo
+          ]
+      , shadowingAlternatives
+          [ syntaxForm2ComponentModule cinfo
+          , syntaxForm2ComponentFile cinfo
+          ]
       , -- rarely used partially qualified forms
         syntaxForm3PackageKindComponent pinfo
+      , shadowingAlternatives
+          [ syntaxForm3PackageComponentModule pinfo
+          , syntaxForm3PackageComponentFile pinfo
+          ]
+      , shadowingAlternatives
+          [ syntaxForm3KindComponentModule cinfo
+          , syntaxForm3KindComponentFile cinfo
+          ]
       , syntaxForm3NamespacePackageFilter pinfo
       , -- fully-qualified forms for all and cwd with filter
         syntaxForm3MetaAllFilter
@@ -956,6 +1003,8 @@ syntaxForms
       , syntaxForm4MetaNamespacePackageFilter pinfo
       , -- fully-qualified forms for component, module and file
         syntaxForm5MetaNamespacePackageKindComponent pinfo
+      , syntaxForm7MetaNamespacePackageKindComponentNamespaceModule pinfo
+      , syntaxForm7MetaNamespacePackageKindComponentNamespaceFile pinfo
       ]
     where
       ambiguousAlternatives = Prelude.foldr1 AmbiguousAlternatives
@@ -1017,12 +1066,49 @@ syntaxForm1Component cs =
   syntaxForm1 render $ \str1 _fstatus1 -> do
     guardComponentName str1
     c <- matchComponentName cs str1
-    return (TargetComponent (cinfoPackageId c) (cinfoName c))
+    return (TargetComponent (cinfoPackageId c) (cinfoName c) WholeComponent)
   where
-    render (TargetComponent p c) =
+    render (TargetComponent p c WholeComponent) =
       [TargetStringFileStatus1 (dispC p c) noFileStatus]
     render _ = []
 
+-- | Syntax: module
+--
+-- > cabal build Data.Foo
+syntaxForm1Module :: [KnownComponent] -> Syntax
+syntaxForm1Module cs =
+  syntaxForm1 render $ \str1 _fstatus1 -> do
+    guardModuleName str1
+    let ms = [(m, c) | c <- cs, m <- cinfoModules c]
+    (m, c) <- matchModuleNameAnd ms str1
+    return (TargetComponent (cinfoPackageId c) (cinfoName c) (ModuleTarget m))
+  where
+    render (TargetComponent _p _c (ModuleTarget m)) =
+      [TargetStringFileStatus1 (dispM m) noFileStatus]
+    render _ = []
+
+-- | Syntax: file name
+--
+-- > cabal build Data/Foo.hs bar/Main.hsc
+syntaxForm1File :: [KnownPackage] -> Syntax
+syntaxForm1File ps =
+  -- Note there's a bit of an inconsistency here vs the other syntax forms
+  -- for files. For the single-part syntax the target has to point to a file
+  -- that exists (due to our use of matchPackageDirectoryPrefix), whereas for
+  -- all the other forms we don't require that.
+  syntaxForm1 render $ \str1 fstatus1 ->
+    expecting "file" str1 $ do
+      (pkgfile, ~KnownPackage{pinfoId, pinfoComponents}) <-
+        -- always returns the KnownPackage case
+        matchPackageDirectoryPrefix ps fstatus1
+      orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+        (filepath, c) <- matchComponentFile pinfoComponents pkgfile
+        return (TargetComponent pinfoId (cinfoName c) (FileTarget filepath))
+  where
+    render (TargetComponent _p _c (FileTarget f)) =
+      [TargetStringFileStatus1 f noFileStatus]
+    render _ = []
+
 ---
 
 -- | Syntax:  :all
@@ -1110,16 +1196,16 @@ syntaxForm2PackageComponent ps =
       KnownPackage{pinfoId, pinfoComponents} ->
         orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
           c <- matchComponentName pinfoComponents str2
-          return (TargetComponent pinfoId (cinfoName c))
+          return (TargetComponent pinfoId (cinfoName c) WholeComponent)
       -- TODO: the error here ought to say there's no component by that name in
       -- this package, and name the package
       KnownPackageName pn ->
         let cn = mkUnqualComponentName str2
-         in return (TargetComponentUnknown pn (Left cn))
+         in return (TargetComponentUnknown pn (Left cn) WholeComponent)
   where
-    render (TargetComponent p c) =
+    render (TargetComponent p c WholeComponent) =
       [TargetStringFileStatus2 (dispP p) noFileStatus (dispC p c)]
-    render (TargetComponentUnknown pn (Left cn)) =
+    render (TargetComponentUnknown pn (Left cn) WholeComponent) =
       [TargetStringFileStatus2 (dispPN pn) noFileStatus (prettyShow cn)]
     render _ = []
 
@@ -1132,12 +1218,108 @@ syntaxForm2KindComponent cs =
     ckind <- matchComponentKind str1
     guardComponentName str2
     c <- matchComponentKindAndName cs ckind str2
-    return (TargetComponent (cinfoPackageId c) (cinfoName c))
+    return (TargetComponent (cinfoPackageId c) (cinfoName c) WholeComponent)
   where
-    render (TargetComponent p c) =
+    render (TargetComponent p c WholeComponent) =
       [TargetStringFileStatus2 (dispCK c) noFileStatus (dispC p c)]
     render _ = []
 
+-- | Syntax: package : module
+--
+-- > cabal build foo:Data.Foo
+-- > cabal build ./foo:Data.Foo
+-- > cabal build ./foo.cabal:Data.Foo
+syntaxForm2PackageModule :: [KnownPackage] -> Syntax
+syntaxForm2PackageModule ps =
+  syntaxForm2 render $ \str1 fstatus1 str2 -> do
+    guardPackage str1 fstatus1
+    guardModuleName str2
+    p <- matchPackage ps str1 fstatus1
+    case p of
+      KnownPackage{pinfoId, pinfoComponents} ->
+        orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+          let ms = [(m, c) | c <- pinfoComponents, m <- cinfoModules c]
+          (m, c) <- matchModuleNameAnd ms str2
+          return (TargetComponent pinfoId (cinfoName c) (ModuleTarget m))
+      KnownPackageName pn -> do
+        m <- matchModuleNameUnknown str2
+        -- We assume the primary library component of the package:
+        return (TargetComponentUnknown pn (Right $ CLibName LMainLibName) (ModuleTarget m))
+  where
+    render (TargetComponent p _c (ModuleTarget m)) =
+      [TargetStringFileStatus2 (dispP p) noFileStatus (dispM m)]
+    render _ = []
+
+-- | Syntax: component : module
+--
+-- > cabal build foo:Data.Foo
+syntaxForm2ComponentModule :: [KnownComponent] -> Syntax
+syntaxForm2ComponentModule cs =
+  syntaxForm2 render $ \str1 _fstatus1 str2 -> do
+    guardComponentName str1
+    guardModuleName str2
+    c <- matchComponentName cs str1
+    orNoThingIn "component" (cinfoStrName c) $ do
+      let ms = cinfoModules c
+      m <- matchModuleName ms str2
+      return
+        ( TargetComponent
+            (cinfoPackageId c)
+            (cinfoName c)
+            (ModuleTarget m)
+        )
+  where
+    render (TargetComponent p c (ModuleTarget m)) =
+      [TargetStringFileStatus2 (dispC p c) noFileStatus (dispM m)]
+    render _ = []
+
+-- | Syntax: package : filename
+--
+-- > cabal build foo:Data/Foo.hs
+-- > cabal build ./foo:Data/Foo.hs
+-- > cabal build ./foo.cabal:Data/Foo.hs
+syntaxForm2PackageFile :: [KnownPackage] -> Syntax
+syntaxForm2PackageFile ps =
+  syntaxForm2 render $ \str1 fstatus1 str2 -> do
+    guardPackage str1 fstatus1
+    p <- matchPackage ps str1 fstatus1
+    case p of
+      KnownPackage{pinfoId, pinfoComponents} ->
+        orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+          (filepath, c) <- matchComponentFile pinfoComponents str2
+          return (TargetComponent pinfoId (cinfoName c) (FileTarget filepath))
+      KnownPackageName pn ->
+        let filepath = str2
+         in -- We assume the primary library component of the package:
+            return (TargetComponentUnknown pn (Right $ CLibName LMainLibName) (FileTarget filepath))
+  where
+    render (TargetComponent p _c (FileTarget f)) =
+      [TargetStringFileStatus2 (dispP p) noFileStatus f]
+    render _ = []
+
+-- | Syntax: component : filename
+--
+-- > cabal build foo:Data/Foo.hs
+syntaxForm2ComponentFile :: [KnownComponent] -> Syntax
+syntaxForm2ComponentFile cs =
+  syntaxForm2 render $ \str1 _fstatus1 str2 -> do
+    guardComponentName str1
+    c <- matchComponentName cs str1
+    orNoThingIn "component" (cinfoStrName c) $ do
+      (filepath, _) <- matchComponentFile [c] str2
+      return
+        ( TargetComponent
+            (cinfoPackageId c)
+            (cinfoName c)
+            (FileTarget filepath)
+        )
+  where
+    render (TargetComponent p c (FileTarget f)) =
+      [TargetStringFileStatus2 (dispC p c) noFileStatus f]
+    render _ = []
+
+---
+
 -- | Syntax: :all : filter
 --
 -- > cabal build :all:tests
@@ -1204,17 +1386,123 @@ syntaxForm3PackageKindComponent ps =
       KnownPackage{pinfoId, pinfoComponents} ->
         orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
           c <- matchComponentKindAndName pinfoComponents ckind str3
-          return (TargetComponent pinfoId (cinfoName c))
+          return (TargetComponent pinfoId (cinfoName c) WholeComponent)
       KnownPackageName pn ->
         let cn = mkComponentName pn ckind (mkUnqualComponentName str3)
-         in return (TargetComponentUnknown pn (Right cn))
+         in return (TargetComponentUnknown pn (Right cn) WholeComponent)
   where
-    render (TargetComponent p c) =
+    render (TargetComponent p c WholeComponent) =
       [TargetStringFileStatus3 (dispP p) noFileStatus (dispCK c) (dispC p c)]
-    render (TargetComponentUnknown pn (Right c)) =
+    render (TargetComponentUnknown pn (Right c) WholeComponent) =
       [TargetStringFileStatus3 (dispPN pn) noFileStatus (dispCK c) (dispC' pn c)]
     render _ = []
 
+-- | Syntax: package : component : module
+--
+-- > cabal build foo:foo:Data.Foo
+-- > cabal build foo/:foo:Data.Foo
+-- > cabal build foo.cabal:foo:Data.Foo
+syntaxForm3PackageComponentModule :: [KnownPackage] -> Syntax
+syntaxForm3PackageComponentModule ps =
+  syntaxForm3 render $ \str1 fstatus1 str2 str3 -> do
+    guardPackage str1 fstatus1
+    guardComponentName str2
+    guardModuleName str3
+    p <- matchPackage ps str1 fstatus1
+    case p of
+      KnownPackage{pinfoId, pinfoComponents} ->
+        orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+          c <- matchComponentName pinfoComponents str2
+          orNoThingIn "component" (cinfoStrName c) $ do
+            let ms = cinfoModules c
+            m <- matchModuleName ms str3
+            return (TargetComponent pinfoId (cinfoName c) (ModuleTarget m))
+      KnownPackageName pn -> do
+        let cn = mkUnqualComponentName str2
+        m <- matchModuleNameUnknown str3
+        return (TargetComponentUnknown pn (Left cn) (ModuleTarget m))
+  where
+    render (TargetComponent p c (ModuleTarget m)) =
+      [TargetStringFileStatus3 (dispP p) noFileStatus (dispC p c) (dispM m)]
+    render (TargetComponentUnknown pn (Left c) (ModuleTarget m)) =
+      [TargetStringFileStatus3 (dispPN pn) noFileStatus (dispCN c) (dispM m)]
+    render _ = []
+
+-- | Syntax: namespace : component : module
+--
+-- > cabal build lib:foo:Data.Foo
+syntaxForm3KindComponentModule :: [KnownComponent] -> Syntax
+syntaxForm3KindComponentModule cs =
+  syntaxForm3 render $ \str1 _fstatus1 str2 str3 -> do
+    ckind <- matchComponentKind str1
+    guardComponentName str2
+    guardModuleName str3
+    c <- matchComponentKindAndName cs ckind str2
+    orNoThingIn "component" (cinfoStrName c) $ do
+      let ms = cinfoModules c
+      m <- matchModuleName ms str3
+      return
+        ( TargetComponent
+            (cinfoPackageId c)
+            (cinfoName c)
+            (ModuleTarget m)
+        )
+  where
+    render (TargetComponent p c (ModuleTarget m)) =
+      [TargetStringFileStatus3 (dispCK c) noFileStatus (dispC p c) (dispM m)]
+    render _ = []
+
+-- | Syntax: package : component : filename
+--
+-- > cabal build foo:foo:Data/Foo.hs
+-- > cabal build foo/:foo:Data/Foo.hs
+-- > cabal build foo.cabal:foo:Data/Foo.hs
+syntaxForm3PackageComponentFile :: [KnownPackage] -> Syntax
+syntaxForm3PackageComponentFile ps =
+  syntaxForm3 render $ \str1 fstatus1 str2 str3 -> do
+    guardPackage str1 fstatus1
+    guardComponentName str2
+    p <- matchPackage ps str1 fstatus1
+    case p of
+      KnownPackage{pinfoId, pinfoComponents} ->
+        orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+          c <- matchComponentName pinfoComponents str2
+          orNoThingIn "component" (cinfoStrName c) $ do
+            (filepath, _) <- matchComponentFile [c] str3
+            return (TargetComponent pinfoId (cinfoName c) (FileTarget filepath))
+      KnownPackageName pn ->
+        let cn = mkUnqualComponentName str2
+            filepath = str3
+         in return (TargetComponentUnknown pn (Left cn) (FileTarget filepath))
+  where
+    render (TargetComponent p c (FileTarget f)) =
+      [TargetStringFileStatus3 (dispP p) noFileStatus (dispC p c) f]
+    render (TargetComponentUnknown pn (Left c) (FileTarget f)) =
+      [TargetStringFileStatus3 (dispPN pn) noFileStatus (dispCN c) f]
+    render _ = []
+
+-- | Syntax: namespace : component : filename
+--
+-- > cabal build lib:foo:Data/Foo.hs
+syntaxForm3KindComponentFile :: [KnownComponent] -> Syntax
+syntaxForm3KindComponentFile cs =
+  syntaxForm3 render $ \str1 _fstatus1 str2 str3 -> do
+    ckind <- matchComponentKind str1
+    guardComponentName str2
+    c <- matchComponentKindAndName cs ckind str2
+    orNoThingIn "component" (cinfoStrName c) $ do
+      (filepath, _) <- matchComponentFile [c] str3
+      return
+        ( TargetComponent
+            (cinfoPackageId c)
+            (cinfoName c)
+            (FileTarget filepath)
+        )
+  where
+    render (TargetComponent p c (FileTarget f)) =
+      [TargetStringFileStatus3 (dispCK c) noFileStatus (dispC p c) f]
+    render _ = []
+
 syntaxForm3NamespacePackageFilter :: [KnownPackage] -> Syntax
 syntaxForm3NamespacePackageFilter ps =
   syntaxForm3 render $ \str1 _fstatus1 str2 str3 -> do
@@ -1272,17 +1560,114 @@ syntaxForm5MetaNamespacePackageKindComponent ps =
       KnownPackage{pinfoId, pinfoComponents} ->
         orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
           c <- matchComponentKindAndName pinfoComponents ckind str5
-          return (TargetComponent pinfoId (cinfoName c))
+          return (TargetComponent pinfoId (cinfoName c) WholeComponent)
       KnownPackageName pn ->
         let cn = mkComponentName pn ckind (mkUnqualComponentName str5)
-         in return (TargetComponentUnknown pn (Right cn))
+         in return (TargetComponentUnknown pn (Right cn) WholeComponent)
   where
-    render (TargetComponent p c) =
+    render (TargetComponent p c WholeComponent) =
       [TargetStringFileStatus5 "" "pkg" (dispP p) (dispCK c) (dispC p c)]
-    render (TargetComponentUnknown pn (Right c)) =
+    render (TargetComponentUnknown pn (Right c) WholeComponent) =
       [TargetStringFileStatus5 "" "pkg" (dispPN pn) (dispCK c) (dispC' pn c)]
     render _ = []
 
+-- | Syntax: :pkg : package : namespace : component : module : module
+--
+-- > cabal build :pkg:foo:lib:foo:module:Data.Foo
+syntaxForm7MetaNamespacePackageKindComponentNamespaceModule
+  :: [KnownPackage] -> Syntax
+syntaxForm7MetaNamespacePackageKindComponentNamespaceModule ps =
+  syntaxForm7 render $ \str1 str2 str3 str4 str5 str6 str7 -> do
+    guardNamespaceMeta str1
+    guardNamespacePackage str2
+    guardPackageName str3
+    ckind <- matchComponentKind str4
+    guardComponentName str5
+    guardNamespaceModule str6
+    p <- matchPackage ps str3 noFileStatus
+    case p of
+      KnownPackage{pinfoId, pinfoComponents} ->
+        orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+          c <- matchComponentKindAndName pinfoComponents ckind str5
+          orNoThingIn "component" (cinfoStrName c) $ do
+            let ms = cinfoModules c
+            m <- matchModuleName ms str7
+            return (TargetComponent pinfoId (cinfoName c) (ModuleTarget m))
+      KnownPackageName pn -> do
+        let cn = mkComponentName pn ckind (mkUnqualComponentName str2)
+        m <- matchModuleNameUnknown str7
+        return (TargetComponentUnknown pn (Right cn) (ModuleTarget m))
+  where
+    render (TargetComponent p c (ModuleTarget m)) =
+      [ TargetStringFileStatus7
+          ""
+          "pkg"
+          (dispP p)
+          (dispCK c)
+          (dispC p c)
+          "module"
+          (dispM m)
+      ]
+    render (TargetComponentUnknown pn (Right c) (ModuleTarget m)) =
+      [ TargetStringFileStatus7
+          ""
+          "pkg"
+          (dispPN pn)
+          (dispCK c)
+          (dispC' pn c)
+          "module"
+          (dispM m)
+      ]
+    render _ = []
+
+-- | Syntax: :pkg : package : namespace : component : file : filename
+--
+-- > cabal build :pkg:foo:lib:foo:file:Data/Foo.hs
+syntaxForm7MetaNamespacePackageKindComponentNamespaceFile
+  :: [KnownPackage] -> Syntax
+syntaxForm7MetaNamespacePackageKindComponentNamespaceFile ps =
+  syntaxForm7 render $ \str1 str2 str3 str4 str5 str6 str7 -> do
+    guardNamespaceMeta str1
+    guardNamespacePackage str2
+    guardPackageName str3
+    ckind <- matchComponentKind str4
+    guardComponentName str5
+    guardNamespaceFile str6
+    p <- matchPackage ps str3 noFileStatus
+    case p of
+      KnownPackage{pinfoId, pinfoComponents} ->
+        orNoThingIn "package" (prettyShow (packageName pinfoId)) $ do
+          c <- matchComponentKindAndName pinfoComponents ckind str5
+          orNoThingIn "component" (cinfoStrName c) $ do
+            (filepath, _) <- matchComponentFile [c] str7
+            return (TargetComponent pinfoId (cinfoName c) (FileTarget filepath))
+      KnownPackageName pn ->
+        let cn = mkComponentName pn ckind (mkUnqualComponentName str5)
+            filepath = str7
+         in return (TargetComponentUnknown pn (Right cn) (FileTarget filepath))
+  where
+    render (TargetComponent p c (FileTarget f)) =
+      [ TargetStringFileStatus7
+          ""
+          "pkg"
+          (dispP p)
+          (dispCK c)
+          (dispC p c)
+          "file"
+          f
+      ]
+    render (TargetComponentUnknown pn (Right c) (FileTarget f)) =
+      [ TargetStringFileStatus7
+          ""
+          "pkg"
+          (dispPN pn)
+          (dispCK c)
+          (dispC' pn c)
+          "file"
+          f
+      ]
+    render _ = []
+
 ---------------------------------------
 -- Syntax utils
 --
@@ -1312,29 +1697,40 @@ type Match5 =
   -> String
   -> String
   -> Match TargetSelector
+type Match7 =
+  String
+  -> String
+  -> String
+  -> String
+  -> String
+  -> String
+  -> String
+  -> Match TargetSelector
 
 syntaxForm1 :: Renderer -> Match1 -> Syntax
+syntaxForm2 :: Renderer -> Match2 -> Syntax
+syntaxForm3 :: Renderer -> Match3 -> Syntax
+syntaxForm4 :: Renderer -> Match4 -> Syntax
+syntaxForm5 :: Renderer -> Match5 -> Syntax
+syntaxForm7 :: Renderer -> Match7 -> Syntax
 syntaxForm1 render f =
   Syntax QL1 match render
   where
     match = \(TargetStringFileStatus1 str1 fstatus1) ->
       f str1 fstatus1
 
-syntaxForm2 :: Renderer -> Match2 -> Syntax
 syntaxForm2 render f =
   Syntax QL2 match render
   where
     match = \(TargetStringFileStatus2 str1 fstatus1 str2) ->
       f str1 fstatus1 str2
 
-syntaxForm3 :: Renderer -> Match3 -> Syntax
 syntaxForm3 render f =
   Syntax QL3 match render
   where
     match = \(TargetStringFileStatus3 str1 fstatus1 str2 str3) ->
       f str1 fstatus1 str2 str3
 
-syntaxForm4 :: Renderer -> Match4 -> Syntax
 syntaxForm4 render f =
   Syntax QLFull match render
   where
@@ -1342,7 +1738,6 @@ syntaxForm4 render f =
       f str1 str2 str3 str4
     match _ = mzero
 
-syntaxForm5 :: Renderer -> Match5 -> Syntax
 syntaxForm5 render f =
   Syntax QLFull match render
   where
@@ -1350,6 +1745,13 @@ syntaxForm5 render f =
       f str1 str2 str3 str4 str5
     match _ = mzero
 
+syntaxForm7 render f =
+  Syntax QLFull match render
+  where
+    match (TargetStringFileStatus7 str1 str2 str3 str4 str5 str6 str7) =
+      f str1 str2 str3 str4 str5 str6 str7
+    match _ = mzero
+
 dispP :: Package p => p -> String
 dispP = prettyShow . packageName
 
@@ -1362,6 +1764,9 @@ dispC = componentStringName . packageName
 dispC' :: PackageName -> ComponentName -> String
 dispC' = componentStringName
 
+dispCN :: UnqualComponentName -> String
+dispCN = prettyShow
+
 dispK :: ComponentKind -> String
 dispK = showComponentKindShort
 
@@ -1371,6 +1776,9 @@ dispCK = dispK . componentKind
 dispF :: ComponentKind -> String
 dispF = showComponentKindFilterShort
 
+dispM :: ModuleName -> String
+dispM = prettyShow
+
 -------------------------------
 -- Package and component info
 --
@@ -1561,6 +1969,12 @@ guardNamespacePackage = guardToken ["pkg", "package"] "'pkg' namespace"
 guardNamespaceCwd :: String -> Match ()
 guardNamespaceCwd = guardToken ["cwd"] "'cwd' namespace"
 
+guardNamespaceModule :: String -> Match ()
+guardNamespaceModule = guardToken ["mod", "module"] "'module' namespace"
+
+guardNamespaceFile :: String -> Match ()
+guardNamespaceFile = guardToken ["file"] "'file' namespace"
+
 guardToken :: [String] -> String -> String -> Match ()
 guardToken tokens msg s
   | caseFold s `elem` tokens = increaseConfidence
@@ -1772,7 +2186,97 @@ matchComponentKindAndName cs ckind str =
     render c = showComponentKindShort (cinfoKind c) ++ ":" ++ cinfoStrName c
 
 ------------------------------
--- Utils
+-- Matching module targets
+--
+
+guardModuleName :: String -> Match ()
+guardModuleName s =
+  case simpleParsec s :: Maybe ModuleName of
+    Just _ -> increaseConfidence
+    _
+      | all validModuleChar s
+          && not (null s) ->
+          return ()
+      | otherwise -> matchErrorExpected "module name" s
+  where
+    validModuleChar c = isAlphaNum c || c == '.' || c == '_' || c == '\''
+
+matchModuleName :: [ModuleName] -> String -> Match ModuleName
+matchModuleName ms str =
+  orNoSuchThing "module" str (map prettyShow ms) $
+    increaseConfidenceFor $
+      matchInexactly caseFold prettyShow ms str
+
+matchModuleNameAnd :: [(ModuleName, a)] -> String -> Match (ModuleName, a)
+matchModuleNameAnd ms str =
+  orNoSuchThing "module" str (map (prettyShow . fst) ms) $
+    increaseConfidenceFor $
+      matchInexactly caseFold (prettyShow . fst) ms str
+
+matchModuleNameUnknown :: String -> Match ModuleName
+matchModuleNameUnknown str =
+  expecting "module" str $
+    increaseConfidenceFor $
+      matchParse str
+
+------------------------------
+-- Matching file targets
+--
+
+matchPackageDirectoryPrefix
+  :: [KnownPackage]
+  -> FileStatus
+  -> Match (FilePath, KnownPackage)
+matchPackageDirectoryPrefix ps (FileStatusExistsFile filepath) =
+  increaseConfidenceFor $
+    matchDirectoryPrefix pkgdirs filepath
+  where
+    pkgdirs =
+      [ (dir, p)
+      | p@KnownPackage{pinfoDirectory = Just (dir, _)} <- ps
+      ]
+matchPackageDirectoryPrefix _ _ = mzero
+
+matchComponentFile
+  :: [KnownComponent]
+  -> String
+  -> Match (FilePath, KnownComponent)
+matchComponentFile cs str =
+  orNoSuchThing "file" str [] $
+    matchComponentModuleFile cs str
+      <|> matchComponentOtherFile cs str
+
+matchComponentOtherFile
+  :: [KnownComponent]
+  -> String
+  -> Match (FilePath, KnownComponent)
+matchComponentOtherFile cs =
+  matchFile
+    [ (normalise (srcdir </> file), c)
+    | c <- cs
+    , srcdir <- cinfoSrcDirs c
+    , file <-
+        cinfoHsFiles c
+          ++ cinfoCFiles c
+          ++ cinfoJsFiles c
+    ]
+    . normalise
+
+matchComponentModuleFile
+  :: [KnownComponent]
+  -> String
+  -> Match (FilePath, KnownComponent)
+matchComponentModuleFile cs str = do
+  matchFile
+    [ (normalise (d </> toFilePath m), c)
+    | c <- cs
+    , d <- cinfoSrcDirs c
+    , m <- cinfoModules c
+    ]
+    (dropExtension (normalise str)) -- Drop the extension because FileTarget
+    -- is stored without the extension
+
+-- utils
 
 -- | Compare two filepaths for equality using DirActions' canonicalizePath
 -- to normalize AND canonicalize filepaths before comparison.
@@ -1789,6 +2293,25 @@ compareFilePath DirActions{..} fp1 fp2
       c2 <- canonicalizePath fp2
       pure $ equalFilePath c1 c2
 
+matchFile :: [(FilePath, a)] -> FilePath -> Match (FilePath, a)
+matchFile fs =
+  increaseConfidenceFor
+    . matchInexactly caseFold fst fs
+
+matchDirectoryPrefix :: [(FilePath, a)] -> FilePath -> Match (FilePath, a)
+matchDirectoryPrefix dirs filepath =
+  tryEach $
+    [ (file, x)
+    | (dir, x) <- dirs
+    , file <- maybeToList (stripDirectory dir)
+    ]
+  where
+    stripDirectory :: FilePath -> Maybe FilePath
+    stripDirectory dir =
+      joinPath `fmap` stripPrefix (splitDirectories dir) filepathsplit
+
+    filepathsplit = splitDirectories filepath
+
 ------------------------------
 -- Matching monad
 --
@@ -1900,6 +2423,10 @@ matchErrorExpected thing got = NoMatch 0 [MatchErrorExpected thing got]
 matchErrorNoSuch :: String -> String -> [String] -> Match a
 matchErrorNoSuch thing got alts = NoMatch 0 [MatchErrorNoSuch thing got alts]
 
+expecting :: String -> String -> Match a -> Match a
+expecting thing got (NoMatch 0 _) = matchErrorExpected thing got
+expecting _ _ m = m
+
 orNoSuchThing :: String -> String -> [String] -> Match a -> Match a
 orNoSuchThing thing got alts (NoMatch 0 _) = matchErrorNoSuch thing got alts
 orNoSuchThing _ _ _ m = m
@@ -1929,6 +2456,9 @@ inexactMatches xs = Match Inexact 0 xs
 unknownMatch :: a -> Match a
 unknownMatch x = Match Unknown 0 [x]
 
+tryEach :: [a] -> Match a
+tryEach = exactMatches
+
 ------------------------------
 -- Top level match runner
 --
@@ -2059,7 +2589,7 @@ ex1pinfo =
 -}
 {-
 stargets =
-  [ TargetComponent (CExeName "foo")
+  [ TargetComponent (CExeName "foo")  WholeComponent
   , TargetComponent (CExeName "foo") (ModuleTarget (mkMn "Foo"))
   , TargetComponent (CExeName "tst") (ModuleTarget (mkMn "Foo"))
   ]
diff --git a/cabal-install/tests/IntegrationTests2.hs b/cabal-install/tests/IntegrationTests2.hs
index ef40f64a8a6..55ea3747b9f 100644
--- a/cabal-install/tests/IntegrationTests2.hs
+++ b/cabal-install/tests/IntegrationTests2.hs
@@ -57,7 +57,9 @@ import Distribution.Simple.Command
 import qualified Distribution.Simple.Flag as Flag
 import Distribution.System
 import Distribution.Version
+import Distribution.ModuleName (ModuleName)
 import Distribution.Text
+import Distribution.Utils.Path
 import qualified Distribution.Client.CmdHaddockProject as CmdHaddockProject
 import Distribution.Client.Setup (globalStoreDir)
 import Distribution.Client.GlobalFlags (defaultGlobalFlags)
@@ -232,8 +234,40 @@ testTargetSelectors reportSubCase = do
     do Right ts <- readTargetSelectors'
                      [ "p", "lib:p", "p:lib:p", ":pkg:p:lib:p"
                      ,      "lib:q", "q:lib:q", ":pkg:q:lib:q" ]
-       ts @?= replicate 4 (TargetComponent "p-0.1" (CLibName LMainLibName))
-           ++ replicate 3 (TargetComponent "q-0.1" (CLibName LMainLibName))
+       ts @?= replicate 4 (TargetComponent "p-0.1" (CLibName LMainLibName) WholeComponent)
+           ++ replicate 3 (TargetComponent "q-0.1" (CLibName LMainLibName) WholeComponent)
+
+    reportSubCase "module"
+    do Right ts <- readTargetSelectors'
+                     [ "P", "lib:p:P", "p:p:P", ":pkg:p:lib:p:module:P"
+                     , "QQ", "lib:q:QQ", "q:q:QQ", ":pkg:q:lib:q:module:QQ"
+                     , "pexe:PMain" -- p:P or q:QQ would be ambiguous here
+                     , "qexe:QMain" -- package p vs component p
+                     ]
+       ts @?= replicate 4 (TargetComponent "p-0.1" (CLibName LMainLibName) (ModuleTarget "P"))
+           ++ replicate 4 (TargetComponent "q-0.1" (CLibName LMainLibName) (ModuleTarget "QQ"))
+           ++ [ TargetComponent "p-0.1" (CExeName "pexe") (ModuleTarget "PMain")
+              , TargetComponent "q-0.1" (CExeName "qexe") (ModuleTarget "QMain")
+              ]
+
+    reportSubCase "file"
+    do Right ts <- readTargetSelectors'
+                     [ "./P.hs", "p:P.lhs", "lib:p:P.hsc", "p:p:P.hsc",
+                                 ":pkg:p:lib:p:file:P.y"
+                     , "q/QQ.hs", "q:QQ.lhs", "lib:q:QQ.hsc", "q:q:QQ.hsc",
+                                  ":pkg:q:lib:q:file:QQ.y"
+                     , "q/Q.hs", "q:Q.lhs", "lib:q:Q.hsc", "q:q:Q.hsc",
+                                  ":pkg:q:lib:q:file:Q.y"
+                     , "app/Main.hs", "p:app/Main.hs", "exe:ppexe:app/Main.hs", "p:ppexe:app/Main.hs",
+                                  ":pkg:p:exe:ppexe:file:app/Main.hs"
+                     ]
+       ts @?= replicate 5 (TargetComponent "p-0.1" (CLibName LMainLibName) (FileTarget "P"))
+           ++ replicate 5 (TargetComponent "q-0.1" (CLibName LMainLibName) (FileTarget "QQ"))
+           ++ replicate 5 (TargetComponent "q-0.1" (CLibName LMainLibName) (FileTarget "Q"))
+           ++ replicate 5 (TargetComponent "p-0.1" (CExeName "ppexe") (FileTarget ("app" </> "Main.hs")))
+       -- Note there's a bit of an inconsistency here: for the single-part
+       -- syntax the target has to point to a file that exists, whereas for
+       -- all the other forms we don't require that.
 
     cleanProject testdir
   where
@@ -336,6 +370,24 @@ testTargetSelectorAmbiguous reportSubCase = do
                       , mkexe "other2" `withCFiles`  ["Foo"] ]
       ]
 
+    -- File target is ambiguous, part of multiple components
+    reportSubCase "ambiguous: file in multiple comps"
+    assertAmbiguous "Bar.hs"
+      [ mkTargetFile "foo" (CExeName "bar")  "Bar"
+      , mkTargetFile "foo" (CExeName "bar2") "Bar"
+      ]
+      [ mkpkg "foo" [ mkexe "bar"  `withModules` ["Bar"]
+                    , mkexe "bar2" `withModules` ["Bar"] ]
+      ]
+    reportSubCase "ambiguous: file in multiple comps with path"
+    assertAmbiguous ("src" </> "Bar.hs")
+      [ mkTargetFile "foo" (CExeName "bar")  ("src" </> "Bar")
+      , mkTargetFile "foo" (CExeName "bar2") ("src" </> "Bar")
+      ]
+      [ mkpkg "foo" [ mkexe "bar"  `withModules` ["Bar"] `withHsSrcDirs` ["src"]
+                    , mkexe "bar2" `withModules` ["Bar"] `withHsSrcDirs` ["src"] ]
+      ]
+
     -- non-exact case packages and components are ambiguous
     reportSubCase "ambiguous: non-exact-case pkg names"
     assertAmbiguous "Foo"
@@ -347,6 +399,19 @@ testTargetSelectorAmbiguous reportSubCase = do
       , mkTargetComponent "bar" (CExeName "FOO") ]
       [ mkpkg "bar" [mkexe "foo", mkexe "FOO"] ]
 
+    -- exact-case Module or File over non-exact case package or component
+    reportSubCase "unambiguous: module vs non-exact-case pkg, comp"
+    assertUnambiguous "Baz"
+      (mkTargetModule "other" (CExeName "other") "Baz")
+      [ mkpkg "baz" [mkexe "BAZ"]
+      , mkpkg "other" [ mkexe "other"  `withModules` ["Baz"] ]
+      ]
+    reportSubCase "unambiguous: file vs non-exact-case pkg, comp"
+    assertUnambiguous "Baz"
+      (mkTargetFile "other" (CExeName "other") "Baz")
+      [ mkpkg "baz" [mkexe "BAZ"]
+      , mkpkg "other" [ mkexe "other"  `withCFiles` ["Baz"] ]
+      ]
   where
     assertAmbiguous :: String
                     -> [TargetSelector]
@@ -423,13 +488,26 @@ testTargetSelectorAmbiguous reportSubCase = do
     withCFiles exe files =
       exe { buildInfo = (buildInfo exe) { cSources = files } }
 
+    withHsSrcDirs :: Executable -> [FilePath] -> Executable
+    withHsSrcDirs exe srcDirs =
+      exe { buildInfo = (buildInfo exe) { hsSourceDirs = map unsafeMakeSymbolicPath srcDirs }}
+
+
 mkTargetPackage :: PackageId -> TargetSelector
 mkTargetPackage pkgid =
     TargetPackage TargetExplicitNamed [pkgid] Nothing
 
 mkTargetComponent :: PackageId -> ComponentName -> TargetSelector
 mkTargetComponent pkgid cname =
-    TargetComponent pkgid cname
+    TargetComponent pkgid cname WholeComponent
+
+mkTargetModule :: PackageId -> ComponentName -> ModuleName -> TargetSelector
+mkTargetModule pkgid cname mname =
+    TargetComponent pkgid cname (ModuleTarget mname)
+
+mkTargetFile :: PackageId -> ComponentName -> String -> TargetSelector
+mkTargetFile pkgid cname fname =
+    TargetComponent pkgid cname (FileTarget fname)
 
 mkTargetAllPackages :: TargetSelector
 mkTargetAllPackages = TargetAllPackages Nothing
@@ -527,23 +605,23 @@ testTargetProblemsCommon config0 = do
             -- benchmarks from packages that are not local to the project
           , ( \_ -> TargetComponentNotProjectLocal
                       (pkgIdMap Map.! "filepath") (CTestName "filepath-tests")
-
+                      WholeComponent
             , mkTargetComponent (pkgIdMap Map.! "filepath")
                                 (CTestName "filepath-tests") )
 
             -- Components can be explicitly @buildable: False@
-          , ( \_ -> TargetComponentNotBuildable "q-0.1" (CExeName "buildable-false")
+          , ( \_ -> TargetComponentNotBuildable "q-0.1" (CExeName "buildable-false") WholeComponent
             , mkTargetComponent "q-0.1" (CExeName "buildable-false") )
 
             -- Testsuites and benchmarks can be disabled by the solver if it
             -- cannot satisfy deps
-          , ( \_ -> TargetOptionalStanzaDisabledBySolver "q-0.1" (CTestName "solver-disabled")
+          , ( \_ -> TargetOptionalStanzaDisabledBySolver "q-0.1" (CTestName "solver-disabled") WholeComponent
             , mkTargetComponent "q-0.1" (CTestName "solver-disabled") )
 
             -- Testsuites and benchmarks can be disabled explicitly by the
             -- user via config
           , ( \_ -> TargetOptionalStanzaDisabledByUser
-                      "q-0.1" (CBenchName "user-disabled")
+                      "q-0.1" (CBenchName "user-disabled") WholeComponent
             , mkTargetComponent "q-0.1" (CBenchName "user-disabled") )
 
             -- An unknown package. The target selector resolution should only
@@ -1007,6 +1085,23 @@ testTargetProblemsTest config reportSubCase = do
       , ( const (CmdTest.notTestProblem
                   "p-0.1" (CBenchName "a-benchmark"))
         , mkTargetComponent "p-0.1" (CBenchName "a-benchmark") )
+      ] ++
+      [ ( const (CmdTest.isSubComponentProblem
+                          "p-0.1" cname (ModuleTarget modname))
+        , mkTargetModule "p-0.1" cname modname )
+      | (cname, modname) <- [ (CTestName  "a-testsuite", "TestModule")
+                            , (CBenchName "a-benchmark", "BenchModule")
+                            , (CExeName   "an-exe",      "ExeModule")
+                            , ((CLibName LMainLibName),                 "P")
+                            ]
+      ] ++
+      [ ( const (CmdTest.isSubComponentProblem
+                          "p-0.1" cname (FileTarget fname))
+        , mkTargetFile "p-0.1" cname fname)
+      | (cname, fname) <- [ (CTestName  "a-testsuite", "Test.hs")
+                          , (CBenchName "a-benchmark", "Bench.hs")
+                          , (CExeName   "an-exe",      "Main.hs")
+                          ]
       ]
 
 
@@ -1092,8 +1187,26 @@ testTargetProblemsBench config reportSubCase = do
       , ( const (CmdBench.componentNotBenchmarkProblem
                   "p-0.1" (CTestName "a-testsuite"))
         , mkTargetComponent "p-0.1" (CTestName "a-testsuite") )
+      ] ++
+      [ ( const (CmdBench.isSubComponentProblem
+                          "p-0.1" cname (ModuleTarget modname))
+        , mkTargetModule "p-0.1" cname modname )
+      | (cname, modname) <- [ (CTestName  "a-testsuite", "TestModule")
+                            , (CBenchName "a-benchmark", "BenchModule")
+                            , (CExeName   "an-exe",      "ExeModule")
+                            , ((CLibName LMainLibName),                 "P")
+                            ]
+      ] ++
+      [ ( const (CmdBench.isSubComponentProblem
+                          "p-0.1" cname (FileTarget fname))
+        , mkTargetFile "p-0.1" cname fname)
+      | (cname, fname) <- [ (CTestName  "a-testsuite", "Test.hs")
+                          , (CBenchName "a-benchmark", "Bench.hs")
+                          , (CExeName   "an-exe",      "Main.hs")
+                          ]
       ]
 
+
 testTargetProblemsHaddock :: ProjectConfig -> (String -> IO ()) -> Assertion
 testTargetProblemsHaddock config reportSubCase = do
 
@@ -1185,7 +1298,7 @@ assertProjectDistinctTargets
   :: forall err. (Eq err, Show err) =>
      ElaboratedInstallPlan
   -> (forall k. TargetSelector -> [AvailableTarget k] -> Either (TargetProblem err) [k])
-  -> (forall k. AvailableTarget k  -> Either (TargetProblem err)  k )
+  -> (forall k. SubComponentTarget ->  AvailableTarget k  -> Either (TargetProblem err)  k )
   -> [TargetSelector]
   -> [(UnitId, ComponentName)]
   -> Assertion
@@ -1215,7 +1328,8 @@ assertProjectTargetProblems
   -> (forall k. TargetSelector
              -> [AvailableTarget k]
              -> Either (TargetProblem err) [k])
-  -> (forall k. AvailableTarget k
+  -> (forall k. SubComponentTarget
+             -> AvailableTarget k
              -> Either (TargetProblem err) k )
   -> [(TargetSelector -> TargetProblem err, TargetSelector)]
   -> Assertion
@@ -1235,7 +1349,7 @@ assertTargetProblems
   :: forall err. (Eq err, Show err) =>
      ElaboratedInstallPlan
   -> (forall k. TargetSelector -> [AvailableTarget k] -> Either (TargetProblem err) [k])
-  -> (forall k. AvailableTarget k  -> Either (TargetProblem err)  k )
+  -> (forall k. SubComponentTarget ->  AvailableTarget k  -> Either (TargetProblem err)  k )
   -> [(TargetSelector -> TargetProblem err, TargetSelector)]
   -> Assertion
 assertTargetProblems elaboratedPlan selectPackageTargets selectComponentTarget =
@@ -1620,7 +1734,7 @@ executePlan ((distDirLayout, cabalDirLayout, config, _, buildSettings),
     let targets :: Map.Map UnitId [ComponentTarget]
         targets =
           Map.fromList
-            [ (unitid, [ComponentTarget cname])
+            [ (unitid, [ComponentTarget cname WholeComponent])
             | ts <- Map.elems (availableTargets elaboratedPlan)
             , AvailableTarget {
                 availableTargetStatus = TargetBuildable (unitid, cname) _
diff --git a/cabal-install/tests/UnitTests.hs b/cabal-install/tests/UnitTests.hs
index 82d44bb354e..8434f623e82 100644
--- a/cabal-install/tests/UnitTests.hs
+++ b/cabal-install/tests/UnitTests.hs
@@ -14,6 +14,7 @@ import qualified UnitTests.Distribution.Client.Init
 import qualified UnitTests.Distribution.Client.InstallPlan
 import qualified UnitTests.Distribution.Client.JobControl
 import qualified UnitTests.Distribution.Client.ProjectConfig
+import qualified UnitTests.Distribution.Client.ProjectPlanning
 import qualified UnitTests.Distribution.Client.Store
 import qualified UnitTests.Distribution.Client.Tar
 import qualified UnitTests.Distribution.Client.Targets
@@ -66,6 +67,9 @@ main = do
       , testGroup
           "UnitTests.Distribution.Client.ProjectConfig"
           UnitTests.Distribution.Client.ProjectConfig.tests
+      , testGroup
+          "UnitTests.Distribution.Client.ProjectPlanning"
+          UnitTests.Distribution.Client.ProjectPlanning.tests
       , testGroup
           "Distribution.Client.Store"
           UnitTests.Distribution.Client.Store.tests
diff --git a/cabal-install/tests/UnitTests/Distribution/Client/ProjectPlanning.hs b/cabal-install/tests/UnitTests/Distribution/Client/ProjectPlanning.hs
new file mode 100644
index 00000000000..184cfef5bdf
--- /dev/null
+++ b/cabal-install/tests/UnitTests/Distribution/Client/ProjectPlanning.hs
@@ -0,0 +1,90 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module UnitTests.Distribution.Client.ProjectPlanning (tests) where
+
+import Data.List.NonEmpty
+import Distribution.Client.ProjectPlanning (ComponentTarget (..), SubComponentTarget (..), nubComponentTargets)
+import Distribution.Types.ComponentName
+import Distribution.Types.LibraryName
+import Test.Tasty
+import Test.Tasty.HUnit
+
+tests :: [TestTree]
+tests =
+  [ testGroup "Build Target Tests" buildTargetTests
+  ]
+
+-- ----------------------------------------------------------------------------
+-- Build Target Tests
+-- ----------------------------------------------------------------------------
+
+buildTargetTests :: [TestTree]
+buildTargetTests =
+  [ testGroup "nubComponentTargets" nubComponentTargetsTests
+  ]
+
+nubComponentTargetsTests :: [TestTree]
+nubComponentTargetsTests =
+  [ testCase "Works on empty list" $
+      nubComponentTargets [] @?= ([] :: [(ComponentTarget, NonEmpty Int)])
+  , testCase "Merges targets to same component" $
+      nubComponentTargets
+        [ (mainLibModuleTarget, 1 :: Int)
+        , (mainLibFileTarget, 2)
+        ]
+        @?= [(mainLibWholeCompTarget, 1 :| [2])]
+  , testCase "Merges whole component targets" $
+      nubComponentTargets [(mainLibFileTarget, 2), (mainLibWholeCompTarget, 1 :: Int)]
+        @?= [(mainLibWholeCompTarget, 2 :| [1])]
+  , testCase "Don't merge unrelated targets" $
+      nubComponentTargets
+        [ (mainLibWholeCompTarget, 1 :: Int)
+        , (exeWholeCompTarget, 2)
+        ]
+        @?= [(mainLibWholeCompTarget, pure 1), (exeWholeCompTarget, pure 2)]
+  , testCase "Merge multiple related targets" $
+      nubComponentTargets
+        [ (mainLibWholeCompTarget, 1 :: Int)
+        , (mainLibModuleTarget, 4)
+        , (exeWholeCompTarget, 2)
+        , (exeFileTarget, 3)
+        ]
+        @?= [(mainLibWholeCompTarget, 1 :| [4]), (exeWholeCompTarget, 2 :| [3])]
+  , testCase "Merge related targets, don't merge unrelated ones" $
+      nubComponentTargets
+        [ (mainLibFileTarget, 1 :: Int)
+        , (mainLibModuleTarget, 4)
+        , (exeWholeCompTarget, 2)
+        , (exeFileTarget, 3)
+        , (exe2FileTarget, 5)
+        ]
+        @?= [ (mainLibWholeCompTarget, 1 :| [4])
+            , (exeWholeCompTarget, 2 :| [3])
+            , (exe2WholeCompTarget, 5 :| [])
+            ]
+  ]
+
+-- ----------------------------------------------------------------------------
+-- Utils
+-- ----------------------------------------------------------------------------
+
+mainLibWholeCompTarget :: ComponentTarget
+mainLibWholeCompTarget = ComponentTarget (CLibName LMainLibName) WholeComponent
+
+mainLibModuleTarget :: ComponentTarget
+mainLibModuleTarget = ComponentTarget (CLibName LMainLibName) (ModuleTarget "Lib")
+
+mainLibFileTarget :: ComponentTarget
+mainLibFileTarget = ComponentTarget (CLibName LMainLibName) (FileTarget "./Lib.hs")
+
+exeWholeCompTarget :: ComponentTarget
+exeWholeCompTarget = ComponentTarget (CExeName "exe") WholeComponent
+
+exeFileTarget :: ComponentTarget
+exeFileTarget = ComponentTarget (CExeName "exe") (FileTarget "./Main.hs")
+
+exe2WholeCompTarget :: ComponentTarget
+exe2WholeCompTarget = ComponentTarget (CExeName "exe2") WholeComponent
+
+exe2FileTarget :: ComponentTarget
+exe2FileTarget = ComponentTarget (CExeName "exe2") (FileTarget "./Main2.hs")
diff --git a/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/Main.hs b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/Main.hs
new file mode 100644
index 00000000000..73566f6f203
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/Main.hs
@@ -0,0 +1 @@
+main = putStrLn "Hello World"
diff --git a/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/RunMainBad.cabal b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/RunMainBad.cabal
new file mode 100644
index 00000000000..22a27144592
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/RunMainBad.cabal
@@ -0,0 +1,9 @@
+name: RunMainBad
+version: 1.0
+build-type: Simple
+cabal-version: >= 1.10
+
+executable foo
+    main-is: Main.hs
+    build-depends: base
+    default-language: Haskell2010
diff --git a/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.out b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.out
new file mode 100644
index 00000000000..25b71f37cce
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.out
@@ -0,0 +1,4 @@
+# cabal v2-run
+Resolving dependencies...
+Error: [Cabal-7070]
+The run command can only run an executable as a whole, not files or modules within them, but the target 'Main.hs' refers to the file Main.hs in the executable foo.
diff --git a/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.project b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.project
new file mode 100644
index 00000000000..e6fdbadb439
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.project
@@ -0,0 +1 @@
+packages: .
diff --git a/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.test.hs b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.test.hs
new file mode 100644
index 00000000000..88370b0fae4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewBuild/CmdRun/RunMainBad/cabal.test.hs
@@ -0,0 +1,4 @@
+import Test.Cabal.Prelude
+
+main = cabalTest $ do
+    void . fails $ cabal' "v2-run" ["./Main.hs"]
diff --git a/changelog.d/pr-8966 b/changelog.d/pr-8966
deleted file mode 100644
index cd3b4cb656a..00000000000
--- a/changelog.d/pr-8966
+++ /dev/null
@@ -1,20 +0,0 @@
-synopsis: Drop file and module targets
-packages: Cabal cabal-install
-prs: #8966
-
-description: {
-
-- The ability to specify a single file or a single module as a target has been
-  removed since no versions of Cabal ever supported this feature; and cabal-install
-  would always fallback to targeting (e.g. building) the whole component.
-
-  If you were using a target syntax that includes a file or module name, you
-  can remove them expecting no change in behaviour. In some cases this will
-  cause the target to become ambiguous, and you will have to specify the
-  component instead.
-
-  Another minor change is that it is now possible to use `cabal run` against a
-  source file which is part of a component. The file will be considered like
-  any other and will need the metadata block.
-
-}