From d90c262f573839d85ef82e6b7e4e2db30ebb25d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@dashbit.co>
Date: Sun, 29 Aug 2021 09:49:25 +0200
Subject: [PATCH] Do not touch hashbangs when formatting, closes #11215

---
 lib/elixir/lib/code/formatter.ex              | 20 ++++++-------------
 .../elixir/code_formatter/comments_test.exs   |  3 ++-
 2 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/lib/elixir/lib/code/formatter.ex b/lib/elixir/lib/code/formatter.ex
index 6e49c7aff3..ee7bd84164 100644
--- a/lib/elixir/lib/code/formatter.ex
+++ b/lib/elixir/lib/code/formatter.ex
@@ -238,22 +238,14 @@ defmodule Code.Formatter do
   end
 
   defp format_comment(%{text: text} = comment) do
-    %{comment | text: format_comment_text(text, "")}
+    %{comment | text: format_comment_text(text)}
   end
 
-  defp format_comment_text("##" <> rest, acc), do: format_comment_text("#" <> rest, "#" <> acc)
-
-  defp format_comment_text("#!", acc), do: reverse_with_prefix(acc, "#!")
-  defp format_comment_text("#! " <> _ = rest, acc), do: reverse_with_prefix(acc, rest)
-  defp format_comment_text("#!" <> rest, acc), do: reverse_with_prefix(acc, "#! " <> rest)
-
-  defp format_comment_text("#", acc), do: reverse_with_prefix(acc, "#")
-  defp format_comment_text("# " <> _ = rest, acc), do: reverse_with_prefix(acc, rest)
-  defp format_comment_text("#" <> rest, acc), do: reverse_with_prefix(acc, "# " <> rest)
-
-  defp reverse_with_prefix(acc, prefix) do
-    String.reverse(acc) <> prefix
-  end
+  defp format_comment_text("#"), do: "#"
+  defp format_comment_text("#!" <> rest), do: "#!" <> rest
+  defp format_comment_text("##" <> rest), do: "#" <> format_comment_text("#" <> rest)
+  defp format_comment_text("# " <> rest), do: "# " <> rest
+  defp format_comment_text("#" <> rest), do: "# " <> rest
 
   # If there is a no new line before, we can't gather all followup comments.
   defp gather_comments([%{previous_eol_count: 0} = comment | comments]) do
diff --git a/lib/elixir/test/elixir/code_formatter/comments_test.exs b/lib/elixir/test/elixir/code_formatter/comments_test.exs
index 288cc22460..d2900924ec 100644
--- a/lib/elixir/test/elixir/code_formatter/comments_test.exs
+++ b/lib/elixir/test/elixir/code_formatter/comments_test.exs
@@ -19,7 +19,8 @@ defmodule Code.Formatter.CommentsTest do
     end
 
     test "recognizes hashbangs" do
-      assert_format "#!/usr/bin/env elixir", "#! /usr/bin/env elixir"
+      assert_format "#! /usr/bin/env elixir", "#! /usr/bin/env elixir"
+      assert_format "#!/usr/bin/env elixir", "#!/usr/bin/env elixir"
       assert_same "#!"
     end