Fix Cabal version selection for build-type:Custom

Previously we would pick up Stack's Cabal version with ghc-pkg on the
global package-db. This however ignores that Stack also supports custom
Setup.hs with the Cabal version from the snapshot instead.

In cabal v2-build we have a similar problem. We used to assume that
plan.json's cabal-lib-version is used uniformly across units but this is
similarly untrue.

To fix both of these we re-stage the cabal version query to after
reconfiguring a unit, then we can just lookup the Cabal version in
setup-config.

Fixes #95

3 files changed, 24 insertions, 14 deletions

diff --git a/src/CabalHelper/Compiletime/Cabal.hs b/src/CabalHelper/Compiletime/Cabal.hs
index aad004c..1ecf01f 100644
--- a/src/CabalHelper/Compiletime/Cabal.hs
+++ b/src/CabalHelper/Compiletime/Cabal.hs
@@ -31,6 +31,7 @@ import Data.Version
 import System.Directory
 import System.FilePath
 import System.IO
+import Text.Printf
 
 import Distribution.Verbosity (Verbosity, silent, normal, verbose, deafening)
 
@@ -223,9 +224,18 @@ complainIfNoCabalFile pkgdir Nothing =
 bultinCabalVersion :: CabalVersion
 bultinCabalVersion = CabalVersion $ parseVer VERSION_Cabal
 
-readSetupConfigHeader :: FilePath -> IO (Maybe UnitHeader)
+readSetupConfigHeader :: FilePath -> IO UnitHeader
 readSetupConfigHeader file = bracket (openFile file ReadMode) hClose $ \h -> do
-  parseSetupHeader <$> BS.hGetLine h
+  mhdr <- parseSetupHeader <$> BS.hGetLine h
+  case mhdr of
+    Just hdr@(UnitHeader _PkgId ("Cabal", _hdrCabalVersion) _compId) -> do
+      return hdr
+    Just UnitHeader {uhSetupId=(setup_name, _)} -> panicIO $
+      printf "Unknown Setup package-id in setup-config header '%s': '%s'"
+        (BS8.unpack setup_name) file
+    Nothing -> panicIO $
+      printf "Could not read '%s' header" file
+
 
 parseSetupHeader :: BS.ByteString -> Maybe UnitHeader
 parseSetupHeader header = case BS8.words header of
diff --git a/src/CabalHelper/Compiletime/Compile.hs b/src/CabalHelper/Compiletime/Compile.hs
index 2993906..4c92fba 100644
--- a/src/CabalHelper/Compiletime/Compile.hs
+++ b/src/CabalHelper/Compiletime/Compile.hs
@@ -91,7 +91,7 @@ data CompilationProductScope = CPSGlobal | CPSProject
 type CompHelperEnv = CompHelperEnv' CabalVersion
 data CompHelperEnv' cv = CompHelperEnv
   { cheCabalVer :: !cv
-  , chePkgDb    :: !(Maybe PackageDbDir)
+  , chePkgDb    :: ![PackageDbDir]
   -- ^ A package-db where we are guaranteed to find Cabal-`cheCabalVer`.
   , cheProjDir  :: !FilePath
   , chePlanJson :: !(Maybe PlanJson)
@@ -120,7 +120,7 @@ compileHelper' CompHelperEnv {..} = do
     CabalVersion cabalVerPlain -> do
       runMaybeT $ msum $ map (\f -> f ghcVer cabalVerPlain) $
         case chePkgDb of
-          Nothing ->
+          [] ->
             [ compileWithCabalV2Inplace
             , compileWithCabalV2GhcEnv
             , compileCabalSource
@@ -128,8 +128,8 @@ compileHelper' CompHelperEnv {..} = do
             , compileGlobal
             , compileWithCabalInPrivatePkgDb
             ]
-          Just db ->
-            [ ((.).(.)) liftIO (compilePkgDb db)
+          dbs ->
+            [ ((.).(.)) liftIO (compilePkgDbs dbs)
             ]
   appdir <- appCacheDir
   let cp@CompPaths {compExePath} = compPaths appdir cheProjLocalCacheDir comp
@@ -149,11 +149,11 @@ compileHelper' CompHelperEnv {..} = do
 
 -- for relaxed deps: find (sameMajorVersionAs cheCabalVer) . reverse . sort
 
-   compilePkgDb db _ghcVer cabalVer  = return $
+   compilePkgDbs dbs _ghcVer cabalVer = return $
        (,)
          (pure ())
          CompileWithCabalPackage
-           { compPackageSource = GPSPackageDBs [db]
+           { compPackageSource = GPSPackageDBs dbs
            , compCabalVersion  = CabalVersion cabalVer
            , compProductTarget = CPSProject
            }
diff --git a/src/CabalHelper/Compiletime/Types.hs b/src/CabalHelper/Compiletime/Types.hs
index bb36df8..07596a9 100644
--- a/src/CabalHelper/Compiletime/Types.hs
+++ b/src/CabalHelper/Compiletime/Types.hs
@@ -456,8 +456,7 @@ newtype ProjConfModTimes = ProjConfModTimes [(FilePath, EpochTime)]
 
 -- | Project-scope information cache.
 data ProjInfo pt = ProjInfo
-  { piCabalVersion     :: !Version
-  , piPackages         :: !(NonEmpty (Package pt))
+  { piPackages         :: !(NonEmpty (Package pt))
   , piImpl             :: !(ProjInfoImpl pt)
   , piProjConfModTimes :: !ProjConfModTimes
   -- ^ Key for cache invalidation. When this is not equal to the return
@@ -466,13 +465,14 @@ data ProjInfo pt = ProjInfo
 
 data ProjInfoImpl pt where
   ProjInfoV1 ::
-    { piV1SetupHeader :: !UnitHeader
+    { piV1SetupHeader  :: !UnitHeader
+    , piV1CabalVersion :: !CabalVersion
     } -> ProjInfoImpl ('Cabal 'CV1)
 
   ProjInfoV2 ::
-    { piV2Plan        :: !PlanJson
-    , piV2PlanModTime :: !EpochTime
-    , piV2CompilerId  :: !(String, Version)
+    { piV2Plan         :: !PlanJson
+    , piV2PlanModTime  :: !EpochTime
+    , piV2CompilerId   :: !(String, Version)
     } -> ProjInfoImpl ('Cabal 'CV2)
 
   ProjInfoStack :: ProjInfoImpl 'Stack