From 7e05c152198c03f2e33aece701af158eb939e0e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gr=C3=B6ber?= <dxld@darkboxed.org>
Date: Wed, 11 May 2016 15:27:11 +0200
Subject: [PATCH] 'debug' shouldn't fail if 'cabal' is not installed

which seems to be more common that you'd think
---
 Language/Haskell/GhcMod/Debug.hs | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/Language/Haskell/GhcMod/Debug.hs b/Language/Haskell/GhcMod/Debug.hs
index 48f7137..59673e0 100644
--- a/Language/Haskell/GhcMod/Debug.hs
+++ b/Language/Haskell/GhcMod/Debug.hs
@@ -9,6 +9,7 @@ import qualified Data.Set as Set
 import Data.Char
 import Data.Version
 import Data.List.Split
+import System.Directory
 import Text.PrettyPrint
 import Language.Haskell.GhcMod.Monad
 import Language.Haskell.GhcMod.Types
@@ -76,8 +77,14 @@ cabalDebug = do
         srcOpts     = Map.map gmcGhcSrcOpts mcs
 
     readProc <- gmReadProcess
-    cabalInstVersion <- liftIO $
-        dropWhileEnd isSpace <$> readProc "cabal" ["--numeric-version"] ""
+    cabalExists <- liftIO $ (/=Nothing) <$> findExecutable "cabal"
+
+    cabalInstVersion <-
+        if cabalExists
+          then liftIO $
+            dropWhileEnd isSpace <$> readProc "cabal" ["--numeric-version"] ""
+          else return ""
+
     packages <- liftIO $ readProc "ghc-pkg" ["list", "--simple-output"] ""
     let cabalPackages = filter ((== ["Cabal"]) . take 1 . splitOn "-") $ splitWhen isSpace packages