From a1f35d7b9942a49ce36d2c5ec5f34d90070452a8 Mon Sep 17 00:00:00 2001
From: Michael Sloan <mgsloan@gmail.com>
Date: Thu, 21 Apr 2016 20:23:02 -0700
Subject: [PATCH] Fix when --exact-configuration is used #1579

---
 src/Stack/Types/Build.hs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Stack/Types/Build.hs b/src/Stack/Types/Build.hs
index f0e4d8dc83..286d02a699 100644
--- a/src/Stack/Types/Build.hs
+++ b/src/Stack/Types/Build.hs
@@ -584,6 +584,7 @@ isStackOpt t = any (`T.isPrefixOf` t)
     , "--enable-benchmarks"
     , "--enable-library-profiling"
     , "--enable-executable-profiling"
+    , "--exact-configuration"
     ] || elem t
     [ "--user"
     ]
@@ -656,7 +657,9 @@ configureOptsNoDir econfig bco deps wanted isLocal package = concat
     -- TODO: instead always enable this when the cabal version is new
     -- enough. That way we'll detect bugs with --exact-configuration
     -- earlier. Cabal also might do less work then.
-    useExactConf = envConfigCabalVersion econfig >= $(mkVersion "1.22")
+    useExactConf = configAllowNewer config
+
+    newerCabal = envConfigCabalVersion econfig >= $(mkVersion "1.22")
 
     -- Unioning atop defaults is needed so that all flags are specified
     -- with --exact-configuration.
@@ -665,7 +668,7 @@ configureOptsNoDir econfig bco deps wanted isLocal package = concat
 
     depOptions = map (uncurry toDepOption) $ Map.toList deps
       where
-        toDepOption = if useExactConf then toDepOption1_22 else toDepOption1_18
+        toDepOption = if newerCabal then toDepOption1_22 else toDepOption1_18
 
     toDepOption1_22 ident gid = concat
         [ "--dependency="