eval: fix multiline outputs

Author: dschrempf

plugins/hls-eval-plugin/src/Ide/Plugin/Eval/Code.hs

@@ -68,12 +68,20 @@ showDiff (Second w) = "NOW " <> w
 showDiff (Both w _) = w
 
 -- | Compare the expected output recorded in the 'EvalExpr' with the actual
--- output @out@. When diffing is enabled and there is a recorded output, return
--- a line-by-line diff (see 'showDiffs'); otherwise return @out@ unchanged.
+-- output @out@, returning the result as one 'T.Text' per line. When diffing is
+-- enabled and there is a recorded output, return a line-by-line diff (see
+-- 'showDiffs'); otherwise return @out@ unchanged.
+--
+-- @out@ is normalised to one element per line first: a multi-line result
+-- arrives here as a single element with embedded newlines, whereas the recorded
+-- output is already split per line, and 'getDiff' compares element-wise. Without
+-- this, identical multi-line results would be reported as entirely changed.
 evalExprCheck :: Bool -> (Section, EvalExpr) -> [T.Text] -> [T.Text]
 evalExprCheck diff (section, evalExpr) out
-    | not diff || null (evalExprOutput evalExpr) || sectionLanguage section == Plain = out
-    | otherwise = showDiffs $ getDiff (map T.pack $ evalExprOutput evalExpr) out
+    | not diff || null (evalExprOutput evalExpr) || sectionLanguage section == Plain = outLines
+    | otherwise = showDiffs $ getDiff (map T.pack $ evalExprOutput evalExpr) outLines
+  where
+    outLines = concatMap T.lines out
 
 -- | The number of (expression lines, result lines) an 'EvalExpr' occupies.
 evalExprLengths :: EvalExpr -> (Int, Int)

plugins/hls-eval-plugin/src/Ide/Plugin/Eval/Handlers.hs

@@ -400,8 +400,7 @@ runEvalExprs recorder EvalConfig{..} e evalExprs = do
         rs <- runEvalExpr e df evalExpr
         dbg $ LogRunEvalExprResults rs
 
-        let checkedResult = evalExprCheck eval_cfg_diff (section, evalExpr) rs
-        let resultLines = concatMap T.lines checkedResult
+        let resultLines = evalExprCheck eval_cfg_diff (section, evalExpr) rs
 
         let edit = asEdit (sectionFormat section) evalExpr (map pad resultLines)
         dbg $ LogRunEvalExprEdits edit

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

@@ -153,6 +153,7 @@ tests =
   , goldenWithEval "Variable 'it' works" "TIt" "hs"
   , testGroup "configuration"
     [ goldenWithEval' "Give 'WAS' by default" "TDiff" "hs" "expected.default"
+    , goldenWithEval "Refreshing an identical multi-line result is a no-op" "TDiffMultiline" "hs"
     , goldenWithEvalConfig' "Give the result only if diff is off" "TDiff" "hs" "expected.no-diff" diffOffConfig
     , goldenWithEvalConfig' "Evaluates to exception (not marked)" "TException" "hs" "expected.nomark" (exceptionConfig False)
     , goldenWithEvalConfig' "Evaluates to exception (with mark)" "TException" "hs" "expected.marked" (exceptionConfig True)

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

@@ -0,0 +1,6 @@
+module TDiffMultiline where
+
+-- |
+-- >>> putStrLn "Hello," >> pure "World!"
+-- Hello,
+-- "World!"

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

@@ -0,0 +1,6 @@
+module TDiffMultiline where
+
+-- |
+-- >>> putStrLn "Hello," >> pure "World!"
+-- Hello,
+-- "World!"