From 4d650bc25737a4d2c0dcc9d4c845688cb5dc85ce Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Sat, 22 Jun 2019 09:29:33 +0900
Subject: [PATCH] Fix over-expansion

* test/lib/minitest/unit.rb (MiniTest::Assertions#mu_pp_for_diff):
  do not expand escaped backslash followed by 'n'.
---
 test/lib/minitest/unit.rb           | 2 +-
 test/minitest/test_minitest_unit.rb | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/test/lib/minitest/unit.rb b/test/lib/minitest/unit.rb
index 25fd15d0937b8d..6ba1c707e6eb20 100644
--- a/test/lib/minitest/unit.rb
+++ b/test/lib/minitest/unit.rb
@@ -179,7 +179,7 @@ def mu_pp obj
     # uses mu_pp to do the first pass and then cleans it up.
 
     def mu_pp_for_diff obj
-      mu_pp(obj).gsub(/\\n/, "\n").gsub(/:0x[a-fA-F0-9]{4,}/m, ':0xXXXXXX')
+      mu_pp(obj).gsub(/(?<!\\)(?:\\\\)*\K\\n/, "\n").gsub(/:0x[a-fA-F0-9]{4,}/m, ':0xXXXXXX')
     end
 
     def _assertions= n # :nodoc:
diff --git a/test/minitest/test_minitest_unit.rb b/test/minitest/test_minitest_unit.rb
index d790a377c7b7e9..c6c8830f20c8a4 100644
--- a/test/minitest/test_minitest_unit.rb
+++ b/test/minitest/test_minitest_unit.rb
@@ -868,6 +868,13 @@ def test_assert_equal_different_short_multiline
     end
   end
 
+  def test_assert_equal_different_escaped_newline
+    msg = "--- expected\n+++ actual\n@@ -1,2 +1,2 @@\n \"xxx\n-a\\\\nb\"\n+a\\\\nc\"\n"
+    util_assert_triggered msg do
+      @tc.assert_equal "xxx\na\\nb", "xxx\na\\nc"
+    end
+  end
+
   def test_assert_in_delta
     @tc.assert_in_delta 0.0, 1.0 / 1000, 0.1
   end