Add pre and post build hooks

Run a program (named "preBuildHook") before doing a package build and
another program (named "postBuildHook") after the package is built.

These two programs need to be in ~/.cabal/hooks/ directory. If two or
more projects need to use different hooks, dispatch can be done using
environment variables.

Co-authored: Moritz Angermann <[email protected]>

Author: erikd

cabal-install/src/Distribution/Client/ProjectBuilding/UnpackedPackage.hs

@@ -101,6 +101,7 @@ import qualified Data.List.NonEmpty as NE
 
 import Control.Exception (ErrorCall, Handler (..), SomeAsyncException, assert, catches)
 import System.Directory (canonicalizePath, createDirectoryIfMissing, doesDirectoryExist, doesFileExist, removeFile)
+import System.Environment (getEnv)
 import System.FilePath (dropDrive, normalise, takeDirectory, (<.>), (</>))
 import System.IO (Handle, IOMode (AppendMode), withFile)
 import System.Semaphore (SemaphoreName (..))
@@ -678,7 +679,32 @@ buildAndInstallUnpackedPackage
           runConfigure
         PBBuildPhase{runBuild} -> do
           noticeProgress ProgressBuilding
-          runBuild
+          hookDir <- (</> ".cabal/hooks") <$> getEnv "HOME"
+          -- run preBuildHook. If it returns with 0, we assume the build was
+          -- successful. If not, run the build.
+          code <-
+            rawSystemExitCode
+              verbosity
+              (Just srcdir)
+              (hookDir </> "preBuildHook")
+              [ (unUnitId $ installedUnitId rpkg)
+              , (getSymbolicPath srcdir)
+              , (getSymbolicPath builddir)
+              ]
+              `catchIO` (\_ -> return (ExitFailure 10))
+          when (code /= ExitSuccess) $ do
+            runBuild
+          -- not sure, if we want to care about a failed postBuildHook?
+          void $
+            rawSystemExitCode
+              verbosity
+              (Just srcdir)
+              (hookDir </> "postBuildHook")
+              [ (unUnitId $ installedUnitId rpkg)
+              , (getSymbolicPath srcdir)
+              , (getSymbolicPath builddir)
+              ]
+              `catchIO` (\_ -> return (ExitFailure 10))
         PBHaddockPhase{runHaddock} -> do
           noticeProgress ProgressHaddock
           runHaddock