Don’t strip trailing newlines at the end of the document

Author: quchen

prettyprinter/src/Data/Text/Prettyprint/Doc/Internal.hs

@@ -1490,9 +1490,7 @@ removeTrailingWhitespace = go (RecordedWhitespace [] 0)
     -- release only the necessary ones.
     go (RecordedWhitespace withheldLines withheldSpaces) = \sds -> case sds of
         SFail -> SFail
-        SEmpty -> if null withheldLines
-            then SEmpty
-            else SLine 0 SEmpty -- do not remove the last newline, Unix-style
+        SEmpty -> foldr (\_i sds' -> SLine 0 sds') SEmpty withheldLines
         SChar c rest
             | c == ' ' -> go (RecordedWhitespace withheldLines (withheldSpaces+1)) rest
             | otherwise -> commitSpaces

prettyprinter/test/Testsuite/Main.hs

@@ -71,7 +71,7 @@ tests = testGroup "Tests"
             , testCase "Keep single trailing newline"
                        removeTrailingWhitespaceKeepTrailingNewline
             , testCase "Reduce to single trailing newline"
-                       removeTrailingWhitespaceReduceToSingleTrailingNewline
+                       removeTrailingWhitespaceInTrailingNewlines
             ]
         ]
     ]
@@ -262,9 +262,9 @@ removeTrailingWhitespaceKeepLonelyTrailingNewline
         sdoc = SChar 'x' (SLine 0 SEmpty)
     in assertEqual "" sdoc (removeTrailingWhitespace sdoc)
 
-removeTrailingWhitespaceReduceToSingleTrailingNewline :: Assertion
-removeTrailingWhitespaceReduceToSingleTrailingNewline
+removeTrailingWhitespaceInTrailingNewlines :: Assertion
+removeTrailingWhitespaceInTrailingNewlines
   = let sdoc :: SimpleDocStream ()
         sdoc = SChar 'x' (SLine 2 (SLine 2 SEmpty))
-        sdoc' = SChar 'x' (SLine 0 SEmpty)
+        sdoc' = SChar 'x' (SLine 0 (SLine 0 SEmpty))
     in assertEqual "" sdoc' (removeTrailingWhitespace sdoc)