core: add roundtrip prop for DerivedPath

Author: sorki

hnix-store-core/hnix-store-core.cabal

@@ -125,6 +125,7 @@ test-suite format-tests
   main-is: Driver.hs
   other-modules:
     Derivation
+    DerivedPath
     ContentAddress
     NarFormat
     Hash

hnix-store-core/src/System/Nix/DerivedPath.hs

@@ -14,6 +14,8 @@ import GHC.Generics (Generic)
 import Data.Set (Set)
 import Data.Text (Text)
 import System.Nix.StorePath (StoreDir, StorePath, StorePathName, InvalidPathError)
+import Test.QuickCheck (Arbitrary)
+import Test.QuickCheck.Arbitrary.Generic (GenericArbitrary(..))
 
 import qualified Data.Set
 import qualified Data.Text
@@ -24,11 +26,17 @@ data OutputsSpec =
   | OutputsSpec_Names (Set StorePathName)
   deriving (Eq, Generic, Ord, Show)
 
+deriving via GenericArbitrary OutputsSpec
+  instance Arbitrary OutputsSpec
+
 data DerivedPath =
     DerivedPath_Opaque StorePath
   | DerivedPath_Built StorePath OutputsSpec
   deriving (Eq, Generic, Ord, Show)
 
+deriving via GenericArbitrary DerivedPath
+  instance Arbitrary DerivedPath
+
 data ParseOutputsError =
     ParseOutputsError_InvalidPath InvalidPathError
   | ParseOutputsError_NoNames
@@ -62,13 +70,13 @@ parseDerivedPath
   -> Either ParseOutputsError DerivedPath
 parseDerivedPath root p =
   case Data.Text.breakOn "!" p of
-    (s,r) ->
+    (s, r) ->
       if Data.Text.null r
       then DerivedPath_Opaque
            <$> (convertError $ System.Nix.StorePath.parsePathFromText root s)
       else DerivedPath_Built
            <$> (convertError $ System.Nix.StorePath.parsePathFromText root s)
-           <*> parseOutputsSpec r
+           <*> parseOutputsSpec (Data.Text.tail r)
 
 derivedPathToText :: StoreDir -> DerivedPath -> Text
 derivedPathToText root = \case

hnix-store-core/tests/DerivedPath.hs

@@ -0,0 +1,19 @@
+module DerivedPath where
+
+import Data.Default.Class (Default(def))
+import Test.Tasty.QuickCheck
+import System.Nix.DerivedPath (DerivedPath(..), OutputsSpec(..))
+
+import qualified Data.Set
+import qualified System.Nix.DerivedPath
+
+prop_derivedPathRoundTrip :: Property
+prop_derivedPathRoundTrip = forAll (arbitrary `suchThat` nonEmptyOutputsSpec_Names) $ \p ->
+  System.Nix.DerivedPath.parseDerivedPath def
+    (System.Nix.DerivedPath.derivedPathToText def p)
+  === pure p
+  where
+    nonEmptyOutputsSpec_Names :: DerivedPath -> Bool
+    nonEmptyOutputsSpec_Names (DerivedPath_Built _ (OutputsSpec_Names set)) =
+      not $ Data.Set.null set
+    nonEmptyOutputsSpec_Names _ = True