From 1968a60265087851918c816f789856e85947b1ce Mon Sep 17 00:00:00 2001
From: Hiroki Tokunaga <tokusan441@gmail.com>
Date: Thu, 4 May 2023 10:47:54 +0900
Subject: [PATCH 1/2] Let language extensions be effective over CPP blocks

---
 TESTS.md       | 11 +++++++++++
 src/HIndent.hs | 19 ++++++++++++-------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/TESTS.md b/TESTS.md
index 7fb83994b..bec1fb820 100644
--- a/TESTS.md
+++ b/TESTS.md
@@ -3397,6 +3397,17 @@ Escaped newlines
   x
 ```
 
+Language extensions are effective across CPP boundaries.
+
+```haskell
+{-# LANGUAGE PatternSynonyms #-}
+#if 1
+pattern Foo :: Int -> Bar
+#else
+pattern Foo :: Int -> Bar
+#endif
+```
+
 ## Literate Haskell
 
 Code with `>`s
diff --git a/src/HIndent.hs b/src/HIndent.hs
index e40fe65fa..40b6b1b10 100644
--- a/src/HIndent.hs
+++ b/src/HIndent.hs
@@ -110,9 +110,10 @@ reformat ::
   -> Maybe FilePath
   -> ByteString
   -> Either ParseError ByteString
-reformat config mexts mfilepath =
+reformat config mexts mfilepath rawCode =
   preserveTrailingNewline
     (fmap (mconcat . intersperse "\n") . mapM processBlock . cppSplitBlocks)
+    rawCode
   where
     processBlock :: CodeBlock -> Either ParseError ByteString
     processBlock (Shebang text) = Right text
@@ -121,12 +122,6 @@ reformat config mexts mfilepath =
       let ls = S8.lines text
           prefix = findPrefix ls
           code = unlines' (map (stripPrefix prefix) ls)
-          allExts =
-            CE.uniqueExtensions $
-            concatMap (\x -> x : extensionImplies x) $
-            mexts ++
-            configExtensions config ++
-            collectLanguageExtensionsFromSource (UTF8.toString code)
        in case parseModule mfilepath allExts (UTF8.toString code) of
             POk _ m ->
               Right $
@@ -176,6 +171,16 @@ reformat config mexts mfilepath =
                else x' <> "\n")
           (f x)
       | otherwise = f x
+    allExts =
+      CE.uniqueExtensions $
+      concatMap (\x -> x : extensionImplies x) $
+      mexts ++ configExtensions config ++ allExtsFromCode
+    allExtsFromCode = concatMap f codeBlocks
+      where
+        f (HaskellSource _ text) =
+          collectLanguageExtensionsFromSource $ UTF8.toString text
+        f _ = []
+    codeBlocks = cppSplitBlocks rawCode
 
 -- | Generate an AST from the given module for debugging.
 testAst :: ByteString -> Either ParseError HsModule'

From 12731b7364d1daf954161151f08940af3cd0306a Mon Sep 17 00:00:00 2001
From: Hiroki Tokunaga <tokusan441@gmail.com>
Date: Thu, 4 May 2023 10:50:33 +0900
Subject: [PATCH 2/2] Add a changelog

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa3778f29..3f5df3060 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@
 - Misplaced comments in do expressions ([#707]).
 - Misplaced comments in case expressions  ([#708]).
 - The bug of extensions specified via pragmas not enabling implied ones ([#727]).
+- Language extensions enabled via pragmas were not effective across CPP boundaries ([#731]).
 
 ### Removed
 
@@ -348,6 +349,7 @@ This version is accidentally pushlished, and is the same as 5.3.3.
 [@uhbif19]: https://github.com/uhbif19
 [@toku-sa-n]: https://github.com/toku-sa-n
 
+[#731]: https://github.com/mihaimaruseac/hindent/pull/731
 [#729]: https://github.com/mihaimaruseac/hindent/pull/729
 [#728]: https://github.com/mihaimaruseac/hindent/pull/728
 [#727]: https://github.com/mihaimaruseac/hindent/pull/727