Having an executable build script implies force = True' in recompile'

This is slight change to the original implementation.  This version
forces a recompile if XMonad detects a custom build script.  The
previous version took into consideration the time stamps of the source
files.

For a custom build script, the source files may be located in another
location, or there could be dependencies unknown to XMonad.  Better to
just always call the build script and let it work out if something
needs to be built.

CHANGES.md

@@ -48,11 +48,6 @@
     instead of `ghc`.  It takes one argument, the name of the
     executable binary it must produce.
 
-    Note: the build script is called whenever `ghc` would have been
-    called.  That means the `xmonad.hs` file (or any files in `lib`
-    need to have newer time stamps than the generated executable in
-    order for the build script to be called.
-
     This fixes #8.  (One of two possible custom build solutions.  See
     the next entry for another solution.)
 

src/XMonad/Core.hs

@@ -570,19 +570,16 @@ recompile force = io $ do
         src  = cfgdir </> "xmonad.hs"
         lib  = cfgdir </> "lib"
         buildscript = cfgdir </> "build"
+
     libTs <- mapM getModTime . Prelude.filter isSource =<< allFiles lib
-    useBuildscript <- do
-      exists <- doesFileExist buildscript
-      if exists
-        then executable <$> getPermissions buildscript
-        else return False
     srcT <- getModTime src
     binT <- getModTime bin
-    buildScriptT  <- getModTime buildscript
-    let addBuildScriptT = if useBuildscript
-                          then (buildScriptT :)
-                          else id
-    if force || any (binT <) ( addBuildScriptT $ srcT : libTs)
+
+    useBuildscript <- do
+      exists <- doesFileExist buildscript
+      if exists then isExecutable buildscript else return False
+
+    if force || useBuildscript || any (binT <) (srcT : libTs)
       then do
         -- temporarily disable SIGCHLD ignoring:
         uninstallSignalHandlers
@@ -610,6 +607,7 @@ recompile force = io $ do
       else return True
  where getModTime f = E.catch (Just <$> getModificationTime f) (\(SomeException _) -> return Nothing)
        isSource = flip elem [".hs",".lhs",".hsc"] . takeExtension
+       isExecutable f = E.catch (executable <$> getPermissions f) (\(SomeException _) -> return False)
        allFiles t = do
             let prep = map (t</>) . Prelude.filter (`notElem` [".",".."])
             cs <- prep <$> E.catch (getDirectoryContents t) (\(SomeException _) -> return [])