Micro cleanup of pull request #233

1 files changed, 12 insertions, 4 deletions

diff --git a/src/Hakyll/Core/UnixFilter.hs b/src/Hakyll/Core/UnixFilter.hs
index e9a2cc1..fd3c335 100644
--- a/src/Hakyll/Core/UnixFilter.hs
+++ b/src/Hakyll/Core/UnixFilter.hs
@@ -19,7 +19,7 @@ import           System.Exit             (ExitCode (..))
 import           System.IO               (Handle, hClose, hFlush, hGetContents,
                                           hPutStr, hSetEncoding, localeEncoding)
 import           System.Process
-import           System.Info
+import qualified System.Info             as System
 
 --------------------------------------------------------------------------------
 import           Hakyll.Core.Compiler
@@ -105,9 +105,17 @@ unixFilterIO :: Monoid o
              -> i
              -> IO (o, String, ExitCode)
 unixFilterIO writer reader programName args input = do
-    let pr = if os == "mingw32"
-             then shell $ unwords (programName : args)
-             else proc programName args
+    -- The problem on Windows is that `proc` is that it is unable to execute
+    -- batch stubs (eg. anything created using 'gem install ...') even if its in
+    -- `$PATH`. A solution to this issue is to execute the batch file explicitly
+    -- using `cmd /c batchfile` but there is no rational way to know where said
+    -- batchfile is on the system. Hence, we detect windows using the
+    -- `System.Info` module and then instead of using `proc` to create the
+    -- process, use `shell` instead which will be able to execute everything
+    -- `proc` can, and this can deal with batch files as well.
+    let pr = if System.os == "mingw32"
+                 then shell $ unwords (programName : args)
+                 else proc programName args
 
     (Just inh, Just outh, Just errh, pid) <-
         createProcess pr