Erase lines affected by CPP before attempting to parse pragmas and im…

…ports

CHANGELOG.md

@@ -14,6 +14,10 @@
   component being formatted it will still be taken into account correctly.
   [Issue 1037](https://github.com/tweag/ormolu/issues/1037).
 
+* Ormolu no longer fails when CPP directly follows the import section (a
+  regression introduced in 0.7.0.0). [Issue
+  1040](https://github.com/tweag/ormolu/issues/1040).
+
 ## Ormolu 0.7.0.0
 
 * Inference of operator fixity information is now more precise and takes

data/examples/other/cpp/cpp-and-imports-out.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE CPP #-}
+
+module Bug where
+
+#ifdef flag
+constant :: Int
+constant = 1312
+#endif

data/examples/other/cpp/cpp-and-imports.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE CPP #-}
+
+module Bug where
+
+#ifdef flag
+constant :: Int
+constant = 1312
+#endif

src/Ormolu/Parser.hs

@@ -54,6 +54,7 @@ import Ormolu.Imports (normalizeImports)
 import Ormolu.Parser.CommentStream
 import Ormolu.Parser.Result
 import Ormolu.Processing.Common
+import Ormolu.Processing.Cpp (eraseCppLines)
 import Ormolu.Processing.Preprocess
 import Ormolu.Utils (incSpanLine, showOutputable, textToStringBuffer)
 
@@ -81,7 +82,7 @@ parseModule config@Config {..} packageFixityMap path rawInput = liftIO $ do
           GHC.Opt_Haddock
           (setDefaultExts baseDynFlags)
       extraOpts = dynOptionToLocatedStr <$> cfgDynOptions
-      rawInputStringBuffer = textToStringBuffer rawInput
+      rawInputStringBuffer = textToStringBuffer (eraseCppLines rawInput)
       beginningLoc =
         mkSrcSpan
           (mkSrcLoc (GHC.mkFastString path) 1 1)

src/Ormolu/Processing/Cpp.hs

@@ -3,6 +3,7 @@
 -- | Support for CPP.
 module Ormolu.Processing.Cpp
   ( cppLines,
+    eraseCppLines,
   )
 where
 
@@ -60,3 +61,14 @@ cppLines input = IntSet.fromAscList $ go Outside (T.lines input `zip` [1 ..])
             inConditional = case state of
               InConditional {} -> True
               _ -> False
+
+-- | Replace all lines affected by CPP with blank lines.
+eraseCppLines :: Text -> Text
+eraseCppLines input =
+  T.unlines . fmap eraseCpp $ T.lines input `zip` [1 ..]
+  where
+    linesToErase = cppLines input
+    eraseCpp (x, i) =
+      if i `IntSet.member` linesToErase
+        then "\n"
+        else x

src/Ormolu/Processing/Preprocess.hs

@@ -104,7 +104,7 @@ linesNotToFormat cppEnabled region@RegionDeltas {..} input =
     totalLines = length (T.lines input)
     regionLines = linesInRegion region input
     (magicDisabled, lineUpdates) = magicDisabledLines regionLines
-    otherDisabled = (mconcat allLines) regionLines
+    otherDisabled = mconcat allLines regionLines
       where
         allLines = [shebangLines, linePragmaLines] <> [cppLines | cppEnabled]