From 9f6b9c53ccf1c0d3bb6d3aa4e183da9936d8e9ec Mon Sep 17 00:00:00 2001
From: Daniel Gröber <dxld@darkboxed.org>
Date: Mon, 11 Jul 2016 06:15:28 +0200
Subject: Fix "empty IORef"

..when component depends on non-existing internal library
---
 CabalHelper/Main.hs | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/CabalHelper/Main.hs b/CabalHelper/Main.hs
index 7c0d15a..a48c2bc 100644
--- a/CabalHelper/Main.hs
+++ b/CabalHelper/Main.hs
@@ -306,10 +306,10 @@ getLibrary pd = unsafePerformIO $ do
   readIORef lr
 
 getLibraryClbi pd lbi = unsafePerformIO $ do
-  lr <- newIORef (error "getLibraryClbi: empty IORef")
+  lr <- newIORef Nothing
 
   withLibLBI pd lbi $ \ lib clbi ->
-      writeIORef lr (lib,clbi)
+      writeIORef lr $ Just (lib,clbi)
 
   readIORef lr
 
@@ -417,21 +417,26 @@ removeInplaceDeps :: Verbosity
                   -> ComponentLocalBuildInfo
                   -> (ComponentLocalBuildInfo, GhcOptions)
 removeInplaceDeps v lbi pd clbi = let
-    (lib, libclbi) = getLibraryClbi pd lbi
-    libbi = libBuildInfo lib
-    liboutdir = componentOutDir lbi (CLib lib)
-    libopts = (componentGhcOptions normal lbi libbi libclbi liboutdir) {
-                                      ghcOptPackageDBs = []
+    (ideps, deps) = partition isInplaceDep (componentPackageDeps clbi)
+    hasIdeps = not $ null ideps
+    libopts =
+      case getLibraryClbi pd lbi of
+        Just (lib, libclbi) | hasIdeps ->
+          let
+            libbi = libBuildInfo lib
+            liboutdir = componentOutDir lbi (CLib lib)
+          in
+            (componentGhcOptions normal lbi libbi libclbi liboutdir) {
+                ghcOptPackageDBs = []
 #if CABAL_MAJOR == 1 && CABAL_MINOR > 22 && CABAL_MINOR < 23
-                                    , ghcOptComponentId = NoFlag
+              , ghcOptComponentId = NoFlag
 #endif
-                                  }
 
-    (ideps, deps) = partition isInplaceDep (componentPackageDeps clbi)
-    hasIdeps = not $ null ideps
+            }
+        _ -> mempty
     clbi' = clbi { componentPackageDeps = deps }
 
-  in (clbi', if hasIdeps then libopts else mempty)
+  in (clbi', libopts)
 
  where
    isInplaceDep :: (InstalledPackageId, PackageId) -> Bool
-- 
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