[commit: haddock] ghc-head, ghc-head1, ie_avails, wip/T14529, wip/new-tree-one-param, wip/revert-ttg-2017-11-20, wip/ttg-2017-10-13, wip/ttg-2017-10-31, wip/ttg-2017-11-06, wip/ttg2-2017-11-10, wip/ttg3-2017-11-12, wip/ttg4-constraints-2017-11-13, wip/ttg6-unrevert-2017-11-22: Haddock: Fix broken lazy IO in prologue reading (#615) (b7d7b7a)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/haddock

On branches: ghc-head,ghc-head1,ie_avails,wip/T14529,wip/new-tree-one-param,wip/revert-ttg-2017-11-20,wip/ttg-2017-10-13,wip/ttg-2017-10-31,wip/ttg-2017-11-06,wip/ttg2-2017-11-10,wip/ttg3-2017-11-12,wip/ttg4-constraints-2017-11-13,wip/ttg6-unrevert-2017-11-22
Link       : http://git.haskell.org/haddock.git/commitdiff/b7d7b7acd42cbe424afde3c8a5a59a0706445343

>---------------------------------------------------------------

commit b7d7b7acd42cbe424afde3c8a5a59a0706445343
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Fri May 12 14:36:08 2017 -0400

    Haddock: Fix broken lazy IO in prologue reading (#615)
    
    We previously used withFile in conjunction with hGetContents. The list returned
    by the latter wasn't completely forced by the time we left the withFile block,
    meaning that we would try to read from a closed handle.


>---------------------------------------------------------------

b7d7b7acd42cbe424afde3c8a5a59a0706445343
 haddock-api/src/Haddock.hs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/haddock-api/src/Haddock.hs b/haddock-api/src/Haddock.hs
index 6af0874..637ccf2 100644
--- a/haddock-api/src/Haddock.hs
+++ b/haddock-api/src/Haddock.hs
@@ -540,9 +540,10 @@ getPrologue :: DynFlags -> [Flag] -> IO (Maybe (MDoc RdrName))
 getPrologue dflags flags =
   case [filename | Flag_Prologue filename <- flags ] of
     [] -> return Nothing
-    [filename] -> withFile filename ReadMode $ \h -> do
+    [filename] -> do
+      h <- openFile filename ReadMode
       hSetEncoding h utf8
-      str <- hGetContents h
+      str <- hGetContents h -- semi-closes the handle
       return . Just $! parseParas dflags str
     _ -> throwE "multiple -p/--prologue options"