Restore BC for initialBuildSteps.

Fixes #4273.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Cabal/Distribution/Simple/Build.hs

@@ -23,6 +23,7 @@ module Distribution.Simple.Build (
     startInterpreter,
 
     initialBuildSteps,
+    componentInitialBuildSteps,
     writeAutogenFiles,
   ) where
 
@@ -105,7 +106,7 @@ build pkg_descr lbi flags suffixes = do
   (\f -> foldM_ f (installedPkgs lbi) componentsToBuild) $ \index target -> do
     let comp = targetComponent target
         clbi = targetCLBI target
-    initialBuildSteps distPref pkg_descr lbi clbi verbosity
+    componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
     let bi     = componentBuildInfo comp
         progs' = addInternalBuildTools pkg_descr lbi bi (withPrograms lbi)
         lbi'   = lbi {
@@ -157,7 +158,7 @@ repl pkg_descr lbi flags suffixes args = do
     [ do let clbi = targetCLBI subtarget
              comp = targetComponent subtarget
              lbi' = lbiForComponent comp lbi
-         initialBuildSteps distPref pkg_descr lbi clbi verbosity
+         componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
          buildComponent verbosity NoFlag
                         pkg_descr lbi' suffixes comp clbi distPref
     | subtarget <- init componentsToBuild ]
@@ -166,7 +167,7 @@ repl pkg_descr lbi flags suffixes args = do
   let clbi = targetCLBI target
       comp = targetComponent target
       lbi' = lbiForComponent comp lbi
-  initialBuildSteps distPref pkg_descr lbi clbi verbosity
+  componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
   replComponent verbosity pkg_descr lbi' suffixes comp clbi distPref
 
 
@@ -605,13 +606,24 @@ replFLib verbosity pkg_descr lbi exe clbi =
     GHC -> GHC.replFLib verbosity NoFlag pkg_descr lbi exe clbi
     _   -> die "A REPL is not supported for this compiler."
 
+-- | Runs 'componentInitialBuildSteps' on every configured component.
 initialBuildSteps :: FilePath -- ^"dist" prefix
+                  -> PackageDescription  -- ^mostly information from the .cabal file
+                  -> LocalBuildInfo -- ^Configuration information
+                  -> Verbosity -- ^The verbosity to use
+                  -> IO ()
+initialBuildSteps distPref pkg_descr lbi verbosity =
+    withAllComponentsInBuildOrder pkg_descr lbi $ \_comp clbi ->
+        componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
+
+-- | Creates the autogenerated files for a particular configured component.
+componentInitialBuildSteps :: FilePath -- ^"dist" prefix
                   -> PackageDescription  -- ^mostly information from the .cabal file
                   -> LocalBuildInfo -- ^Configuration information
                   -> ComponentLocalBuildInfo
                   -> Verbosity -- ^The verbosity to use
                   -> IO ()
-initialBuildSteps _distPref pkg_descr lbi clbi verbosity = do
+componentInitialBuildSteps _distPref pkg_descr lbi clbi verbosity = do
   createDirectoryIfMissingVerbose verbosity True (componentBuildDir lbi clbi)
 
   writeAutogenFiles verbosity pkg_descr lbi clbi

Cabal/Distribution/Simple/Haddock.hs

@@ -194,7 +194,7 @@ haddock pkg_descr lbi suffixes flags' = do
             , fromPackageDescription haddockTarget pkg_descr ]
 
     withAllComponentsInBuildOrder pkg_descr lbi $ \component clbi -> do
-      initialBuildSteps (flag haddockDistPref) pkg_descr lbi clbi verbosity
+      componentInitialBuildSteps (flag haddockDistPref) pkg_descr lbi clbi verbosity
       preprocessComponent pkg_descr component lbi clbi False verbosity suffixes
       let
         doExe com = case (compToExe com) of
@@ -682,7 +682,7 @@ hscolour' onNoHsColour haddockTarget pkg_descr lbi suffixes flags =
         hscolourPref haddockTarget distPref pkg_descr
 
       withAllComponentsInBuildOrder pkg_descr lbi $ \comp clbi -> do
-        initialBuildSteps distPref pkg_descr lbi clbi verbosity
+        componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
         preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
         let
           doExe com = case (compToExe com) of