Support Cabal 3.0

[expipiplus1]

It would be really nice if there was support for a more recent cabal version!

[remexre]

I have a patch for bumping the Cabal dependency to 3.2.0.0, but I don't have new-style builds working yet.

commit 3cc4ebbe0ddc7a74b349b9417e5e5388d9d2694f
Author: Nathan Ringo <[email protected]>
Date:   Wed Jun 24 20:24:45 2020 -0500

    Bumps to Cabal 3.2, not yet supported new-style builds.

diff --git a/.gitignore b/.gitignore
index b6e81f7..8e24af0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 #####=== Haskell ===#####
 
 dist
+dist-newstyle
 cabal-dev
 *.o
 *.hi
diff --git a/src/Cabal/Haddock.hs b/src/Cabal/Haddock.hs
index 49567f7..6977563 100644
--- a/src/Cabal/Haddock.hs
+++ b/src/Cabal/Haddock.hs
@@ -80,7 +80,7 @@ import Distribution.Simple.Utils
          ( die', copyFileTo, warn, notice, intercalate, setupMessage
          , createDirectoryIfMissingVerbose, withTempFileEx, copyFileVerbose
          , withTempDirectoryEx
-         , findFileWithExtension, findFile
+         , findFileWithExtension, findFileEx
          , TempFileOptions(..), defaultTempFileOptions )
 import Distribution.Simple.Glob ( matchDirFileGlob )
 import Distribution.System (buildPlatform)
@@ -89,6 +89,7 @@ import Distribution.Text
 import Distribution.Types.UnqualComponentName
 import Distribution.Utils.NubList
          ( NubListR(), toNubListR, fromNubListR )
+import qualified Distribution.Utils.ShortText as ShortText
 
 import Distribution.Verbosity
 import Language.Haskell.Extension
@@ -299,18 +300,19 @@ fromPackageDescription pkg_descr =
                 argPackageName = Flag $ packageId $ pkg_descr,
                 -- argOutputDir = Dir $ "doc" </> "html" </> display (packageName pkg_descr),
                 argOutputDir = Dir $ display (packageName pkg_descr),
-                argPrologue = Flag $ if null desc then synopsis pkg_descr else desc,
+                argPrologue = Flag . ShortText.fromShortText $
+                  if ShortText.null desc then synopsis pkg_descr else desc,
                 argTitle = Flag $ showPkg ++ subtitle
              }
       where
         desc = PD.description pkg_descr
         showPkg = display (packageId pkg_descr)
-        subtitle | null (synopsis pkg_descr) = ""
-                 | otherwise                 = ": " ++ synopsis pkg_descr
+        subtitle | ShortText.null (synopsis pkg_descr) = ""
+                 | otherwise                 = ": " ++ ShortText.fromShortText (synopsis pkg_descr)
 
 ghcSharedOptions :: BuildInfo
                  -> NubListR String
-ghcSharedOptions = toNubListR . maybe [] id . lookup GHC . sharedOptions
+ghcSharedOptions = toNubListR . maybe [] id . lookup GHC . undefined . sharedOptions
 
 fromLibrary :: Verbosity
             -> FilePath
@@ -654,7 +656,7 @@ getExeSourceFiles :: Verbosity
                      -> IO [(ModuleName.ModuleName, FilePath)]
 getExeSourceFiles verbosity lbi exe clbi = do
     moduleFiles <- getSourceFiles verbosity searchpaths modules
-    srcMainPath <- findFile (hsSourceDirs bi) (modulePath exe)
+    srcMainPath <- findFileEx normal (hsSourceDirs bi) (modulePath exe)
     return ((ModuleName.main, srcMainPath) : moduleFiles)
   where
     bi          = buildInfo exe
diff --git a/standalone-haddock.cabal b/standalone-haddock.cabal
index 80fb166..fe27bd5 100644
--- a/standalone-haddock.cabal
+++ b/standalone-haddock.cabal
@@ -37,7 +37,7 @@ executable standalone-haddock
     Cabal.Simple
   build-depends:
     base >= 4.11 && < 5,
-    Cabal >= 2.4 && < 2.6,
+    Cabal >= 3.2 && < 3.3,
     filepath,
     directory,
     containers,