Implement WantedCompiler parsing

subs/pantry/package.yaml

@@ -87,3 +87,4 @@ tests:
     - pantry
     - hspec
     - exceptions
+    - hedgehog

subs/pantry/src/Pantry/Types.hs

@@ -983,7 +983,12 @@ parseWantedCompiler t0 = maybe (Left $ InvalidWantedCompiler t0) Right $
     Just t1 -> parseGhcjs t1
     Nothing -> T.stripPrefix "ghc-" t0 >>= parseGhc
   where
-    parseGhcjs = undefined
+    parseGhcjs t1 = do
+      let (ghcjsVT, t2) = T.break (== '_') t1
+      ghcjsV <- parseVersion $ T.unpack ghcjsVT
+      ghcVT <- T.stripPrefix "_ghc-" t2
+      ghcV <- parseVersion $ T.unpack ghcVT
+      pure $ WCGhcjs ghcjsV ghcV
     parseGhc = fmap WCGhc . parseVersion . T.unpack
 
 data UnresolvedSnapshotLocation

subs/pantry/test/Pantry/TypesSpec.hs

@@ -0,0 +1,30 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE OverloadedStrings #-}
+module Pantry.TypesSpec (spec) where
+
+import Test.Hspec
+import Hedgehog
+import qualified Hedgehog.Gen as Gen
+import qualified Hedgehog.Range as Range
+import Pantry
+import RIO
+import Distribution.Types.Version (mkVersion)
+
+hh :: HasCallStack => String -> Property -> Spec
+hh name p = it name $ do
+  result <- check p
+  unless result $ throwString "Hedgehog property failed" :: IO ()
+
+spec :: Spec
+spec = do
+  describe "WantedCompiler" $ do
+    hh "parse/render works" $ property $ do
+      wc <- forAll $
+        let ghc = WCGhc <$> genVersion
+            ghcjs = WCGhcjs <$> genVersion <*> genVersion
+            genVersion = mkVersion <$> Gen.list (Range.linear 1 5) (Gen.int (Range.linear 0 100))
+         in Gen.choice [ghc, ghcjs]
+      let text = utf8BuilderToText $ display wc
+      case parseWantedCompiler text of
+        Left e -> throwIO e
+        Right actual -> liftIO $ actual `shouldBe` wc