Test NSelect reduction

hnix.cabal

@@ -623,6 +623,7 @@ test-suite hnix-tests
       ParserTests
       PrettyParseTests
       PrettyTests
+      ReduceExprTests
       TestCommon
       Paths_hnix
   hs-source-dirs:

tests/Main.hs

@@ -26,6 +26,7 @@ import           Nix.Value
 import qualified NixLanguageTests
 import qualified ParserTests
 import qualified PrettyTests
+import qualified ReduceExprTests
 -- import qualified PrettyParseTests
 import           System.Directory
 import           System.Environment
@@ -98,7 +99,8 @@ main = do
       | isJust hpackTestsEnv ] ++
     [ ParserTests.tests
     , EvalTests.tests
-    , PrettyTests.tests ] ++
+    , PrettyTests.tests
+    , ReduceExprTests.tests] ++
     -- [ PrettyParseTests.tests
     --     (fromIntegral (read (fromMaybe "0" prettyTestsEnv) :: Int)) ] ++
     [ evalComparisonTests ] ++

tests/ReduceExprTests.hs

@@ -0,0 +1,34 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# OPTIONS_GHC -fno-warn-name-shadowing #-}
+module ReduceExprTests (tests) where
+import Data.Fix
+import Test.Tasty
+import Test.Tasty.HUnit
+
+import Nix.Atoms
+import Nix.Expr.Types
+import Nix.Expr.Types.Annotated
+import Nix.Reduce (reduceExpr)
+import Nix.Parser
+
+
+tests :: TestTree
+tests = testGroup "Expr Reductions"
+    [ testCase "Non nested NSelect on set should be reduced" $ 
+        cmpReduceResult nonNestedSelect nonNestedSelectExpect 
+    ]
+
+cmpReduceResult :: Result NExprLoc -> NExpr -> Assertion 
+cmpReduceResult r e = do
+    r <- assertSucc r
+    r <- stripAnnotation <$> reduceExpr Nothing r
+    r @?= e
+    where
+        assertSucc (Success a) = pure a
+        assertSucc (Failure d) = assertFailure $ show d
+
+nonNestedSelect :: Result NExprLoc
+nonNestedSelect = parseNixTextLoc "{a=42;}.a"
+
+nonNestedSelectExpect :: NExpr
+nonNestedSelectExpect = Fix . NConstant $ NInt 42