Test multiline eval results

- add test for multiline show instance

See #2907

plugins/hls-eval-plugin/test/Main.hs

@@ -68,6 +68,7 @@ tests =
   , goldenWithEval "Refresh an evaluation" "T5" "hs"
   , goldenWithEval "Refresh an evaluation w/ lets" "T6" "hs"
   , goldenWithEval "Refresh a multiline evaluation" "T7" "hs"
+  , goldenWithEval "Evaluate a multi-line show result" "TMultiResult" "hs" -- Do not escape from comments!
   , testCase "Semantic and Lexical errors are reported" $ do
       evalInFile "T8.hs" "-- >>> noFunctionWithThisName" "-- Variable not in scope: noFunctionWithThisName"
       evalInFile "T8.hs" "-- >>> res = \"a\" + \"bc\"" $

plugins/hls-eval-plugin/test/testdata/TMultiResult.expected.hs

@@ -0,0 +1,13 @@
+module TMultiResult where
+-- test multiline show instance (see #2907)
+
+data Multiline = M {l1 :: String, l2 :: String} deriving Read
+
+instance Show Multiline where
+  show m = "M {\n  l1=" <> show (l1 m) <> ",\n  l2=" <> show (l2 m) <> "\n}"
+
+-- >>> M "first line" "second line"
+-- M {
+--   l1="first line",
+--   l2="second line"
+-- }

plugins/hls-eval-plugin/test/testdata/TMultiResult.hs

@@ -0,0 +1,9 @@
+module TMultiResult where
+-- test multiline show instance (see #2907)
+
+data Multiline = M {l1 :: String, l2 :: String} deriving Read
+
+instance Show Multiline where
+  show m = "M {\n  l1=" <> show (l1 m) <> ",\n  l2=" <> show (l2 m) <> "\n}"
+
+-- >>> M "first line" "second line"