Reject index-states after last known index-state

.gitignore

@@ -83,3 +83,6 @@ bench.html
 
 # Emacs
 .projectile
+
+# I'm unsure how to ignore these generated golden files
+cabal-testsuite/PackageTests/NewUpdate/RejectFutureIndexStates/cabal.out

cabal-install/src/Distribution/Client/CmdUpdate.hs

@@ -98,7 +98,7 @@ import Distribution.Simple.Command
 import System.FilePath (dropExtension, (<.>))
 
 import Distribution.Client.Errors
-import Distribution.Client.IndexUtils.Timestamp (nullTimestamp)
+import Distribution.Client.IndexUtils.Timestamp (Timestamp (NoTimestamp))
 import qualified Hackage.Security.Client as Sec
 
 updateCommand :: CommandUI (NixStyleFlags ())
@@ -257,18 +257,19 @@ updateRepo verbosity _updateFlags repoCtxt (repo, indexState) = do
           updateRepoIndexCache verbosity (RepoIndex repoCtxt repo)
     RepoSecure{} -> repoContextWithSecureRepo repoCtxt repo $ \repoSecure -> do
       let index = RepoIndex repoCtxt repo
-      -- NB: This may be a nullTimestamp if we've never updated before
-      current_ts <- currentIndexTimestamp (lessVerbose verbosity) repoCtxt repo
+      -- NB: This may be a NoTimestamp if we've never updated before
+      current_ts <- currentIndexTimestamp (lessVerbose verbosity) index
       -- NB: always update the timestamp, even if we didn't actually
       -- download anything
       writeIndexTimestamp index indexState
-      ce <-
-        if repoContextIgnoreExpiry repoCtxt
-          then Just `fmap` getCurrentTime
-          else return Nothing
-      updated <- Sec.uncheckClientErrors $ Sec.checkForUpdates repoSecure ce
-      -- this resolves indexState (which could be HEAD) into a timestamp
-      new_ts <- currentIndexTimestamp (lessVerbose verbosity) repoCtxt repo
+
+      updated <- do
+        ce <-
+          if repoContextIgnoreExpiry repoCtxt
+            then Just <$> getCurrentTime
+            else return Nothing
+        Sec.uncheckClientErrors $ Sec.checkForUpdates repoSecure ce
+
       let rname = remoteRepoName (repoRemote repo)
 
       -- Update cabal's internal index as well so that it's not out of sync
@@ -277,14 +278,20 @@ updateRepo verbosity _updateFlags repoCtxt (repo, indexState) = do
         Sec.NoUpdates -> do
           now <- getCurrentTime
           setModificationTime (indexBaseName repo <.> "tar") now
-            `catchIO` (\e -> warn verbosity $ "Could not set modification time of index tarball -- " ++ displayException e)
+            `catchIO` \e ->
+              warn verbosity $ "Could not set modification time of index tarball -- " ++ displayException e
           noticeNoWrap verbosity $
             "Package list of " ++ prettyShow rname ++ " is up to date."
         Sec.HasUpdates -> do
           updateRepoIndexCache verbosity index
           noticeNoWrap verbosity $
             "Package list of " ++ prettyShow rname ++ " has been updated."
 
+      -- This resolves indexState (which could be HEAD) into a timestamp
+      -- This could be null but should not be, since the above guarantees
+      -- we have an updated index.
+      new_ts <- currentIndexTimestamp (lessVerbose verbosity) index
+
       noticeNoWrap verbosity $
         "The index-state is set to " ++ prettyShow (IndexStateTime new_ts) ++ "."
 
@@ -294,7 +301,7 @@ updateRepo verbosity _updateFlags repoCtxt (repo, indexState) = do
 
       -- In case current_ts is a valid timestamp different from new_ts, let
       -- the user know how to go back to current_ts
-      when (current_ts /= nullTimestamp && new_ts /= current_ts) $
+      when (current_ts /= NoTimestamp && new_ts /= current_ts) $
         noticeNoWrap verbosity $
           "To revert to previous state run:\n"
             ++ "    cabal v2-update '"

cabal-install/src/Distribution/Client/Errors.hs

@@ -25,6 +25,9 @@ import Data.ByteString (ByteString)
 import qualified Data.ByteString.Base16 as Base16
 import qualified Data.ByteString.Char8 as BS8
 import Data.List (groupBy)
+import Distribution.Client.IndexUtils.Timestamp
+import Distribution.Client.Types.Repo
+import Distribution.Client.Types.RepoName (RepoName (..))
 import Distribution.Compat.Prelude
 import Distribution.Deprecated.ParseUtils (PWarning, showPWarning)
 import Distribution.Package
@@ -179,6 +182,8 @@ data CabalInstallException
   | FreezeException String
   | PkgSpecifierException [String]
   | CorruptedIndexCache String
+  | UnusableIndexState RemoteRepo Timestamp Timestamp
+  | MissingPackageList RemoteRepo
   deriving (Show, Typeable)
 
 exceptionCodeCabalInstall :: CabalInstallException -> Int
@@ -327,6 +332,8 @@ exceptionCodeCabalInstall e = case e of
   FreezeException{} -> 7156
   PkgSpecifierException{} -> 7157
   CorruptedIndexCache{} -> 7158
+  UnusableIndexState{} -> 7159
+  MissingPackageList{} -> 7160
 
 exceptionMessageCabalInstall :: CabalInstallException -> String
 exceptionMessageCabalInstall e = case e of
@@ -828,6 +835,20 @@ exceptionMessageCabalInstall e = case e of
   FreezeException errs -> errs
   PkgSpecifierException errorStr -> unlines errorStr
   CorruptedIndexCache str -> str
+  UnusableIndexState repoRemote maxFound requested ->
+    "Latest known index-state for '"
+      ++ unRepoName (remoteRepoName repoRemote)
+      ++ "' ("
+      ++ prettyShow maxFound
+      ++ ") is older than the requested index-state ("
+      ++ prettyShow requested
+      ++ ").\nRun 'cabal update' or set the index-state to a value at or before "
+      ++ prettyShow maxFound
+      ++ "."
+  MissingPackageList repoRemote ->
+    "The package list for '"
+      ++ unRepoName (remoteRepoName repoRemote)
+      ++ "' does not exist. Run 'cabal update' to download it."
 
 instance Exception (VerboseException CabalInstallException) where
   displayException :: VerboseException CabalInstallException -> [Char]