From 9f40e1957b79c7a92b86ed5d7aee3d6d33408b9a Mon Sep 17 00:00:00 2001
From: Zhenya Vinogradov <zhenyavinogradov@gmail.com>
Date: Fri, 24 Apr 2020 14:44:54 +0300
Subject: [PATCH] Include cabal-version field into cabal files generated with
 hpack

hpack includes this field itself when it's called from the command line.
Without this field cabal may fail to parse generated cabal files
---
 cabal2nix/Main.hs            | 13 ++++++++++---
 lib/Stack2nix/Project.hs     | 14 +++++++++++---
 plan2nix/Plan2Nix/Project.hs | 13 ++++++++++---
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/cabal2nix/Main.hs b/cabal2nix/Main.hs
index 0f09e41..b7234b2 100644
--- a/cabal2nix/Main.hs
+++ b/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)
diff --git a/lib/Stack2nix/Project.hs b/lib/Stack2nix/Project.hs
index c0f65f7..ace8823 100644
--- a/lib/Stack2nix/Project.hs
+++ b/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
diff --git a/plan2nix/Plan2Nix/Project.hs b/plan2nix/Plan2Nix/Project.hs
index 0ea337e..fbfe041 100644
--- a/plan2nix/Plan2Nix/Project.hs
+++ b/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