Include cabal-version field into cabal files generated with hpack (input-output-hk#85)

hpack includes this field itself when it's called from the command line.
Without this field cabal may fail to parse generated cabal files

Author: zhenyavinogradov

nix-tools/cabal2nix/Main.hs

@@ -92,10 +92,17 @@ findCabalFiles path = doesFileExist (path </> Hpack.packageConfig) >>= \case
       Right r ->
         return $ [InMemory (Just Hpack)
                            (Hpack.decodeResultCabalFile r)
-                           (encodeUtf8 $ Hpack.renderPackage [] (Hpack.decodeResultPackage r))]
+                           (encodeUtf8 $ render r)]
 
-  where encodeUtf8 :: String -> ByteString
-        encodeUtf8 = T.encodeUtf8 . T.pack
+  where
+    render :: Hpack.DecodeResult -> String
+    render r =
+      let body = Hpack.renderPackage [] (Hpack.decodeResultPackage r)
+          cabalVersion = Hpack.decodeResultCabalVersion r
+      in cabalVersion ++ body
+
+    encodeUtf8 :: String -> ByteString
+    encodeUtf8 = T.encodeUtf8 . T.pack
 
 
 expr :: FilePath -> String -> String -> IO (Binding NExpr)

nix-tools/lib/Stack2nix/Project.hs

@@ -30,10 +30,18 @@ findCabalFiles UsePackageYamlFirst path = doesFileExist (path </> Hpack.packageC
       Right r ->
         return $ [InMemory (Just Hpack)
                            (Hpack.decodeResultCabalFile r)
-                           (encodeUtf8 $ Hpack.renderPackage [] (Hpack.decodeResultPackage r))]
+                           (encodeUtf8 $ render r)]
+
+  where
+    render :: Hpack.DecodeResult -> String
+    render r =
+      let body = Hpack.renderPackage [] (Hpack.decodeResultPackage r)
+          cabalVersion = Hpack.decodeResultCabalVersion r
+      in cabalVersion ++ body
+
+    encodeUtf8 :: String -> ByteString
+    encodeUtf8 = T.encodeUtf8 . T.pack
 
-  where encodeUtf8 :: String -> ByteString
-        encodeUtf8 = T.encodeUtf8 . T.pack
 
 findOnlyCabalFiles :: FilePath -> IO [CabalFile]
 findOnlyCabalFiles path = fmap (OnDisk . (path </>)) . filter (isSuffixOf ".cabal") <$> listDirectory path

nix-tools/plan2nix/Plan2Nix/Project.hs

@@ -28,7 +28,14 @@ findCabalFiles path = doesFileExist (path </> Hpack.packageConfig) >>= \case
       Right r ->
         return $ [InMemory (Just Hpack)
                            (Hpack.decodeResultCabalFile r)
-                           (encodeUtf8 $ Hpack.renderPackage [] (Hpack.decodeResultPackage r))]
+                           (encodeUtf8 $ render r)]
 
-  where encodeUtf8 :: String -> ByteString
-        encodeUtf8 = T.encodeUtf8 . T.pack
+  where
+    render :: Hpack.DecodeResult -> String
+    render r =
+      let body = Hpack.renderPackage [] (Hpack.decodeResultPackage r)
+          cabalVersion = Hpack.decodeResultCabalVersion r
+      in cabalVersion ++ body
+
+    encodeUtf8 :: String -> ByteString
+    encodeUtf8 = T.encodeUtf8 . T.pack