From 72d1a289f979ece35858845d867cfa05d8dc6e6d Mon Sep 17 00:00:00 2001
From: Cohen Karnell <7363269+ckarnell@users.noreply.github.com>
Date: Sun, 30 Aug 2026 22:14:07 -0400
Subject: [PATCH] Escape trailing spaces in GitIgnoreSpecPattern.escape()

escape() escaped \ [ ] ! * # ? but not trailing spaces. Git strips
unescaped trailing spaces from a pattern, and the parser here already
relies on that: pattern_to_regex keeps trailing spaces only when the
pattern ends with an escaped space, otherwise it rstrips them. So an
escaped filename that ended with a space no longer matched that file,
e.g. escape("foo ") produced "foo " which the parser reduced to "foo".

Escape each trailing space (space only, matching git's behavior) so the
escaped pattern round-trips. Two existing char-map tests asserted that a
lone space escapes to itself, which is the same round-trip gap; updated
them to expect an escaped space, and added a round-trip test.
---
 pathspec/patterns/gitignore/base.py |  8 ++++++++
 tests/test_02_gitignore_base.py     |  4 ++--
 tests/test_04_gitignore_spec.py     | 12 ++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/pathspec/patterns/gitignore/base.py b/pathspec/patterns/gitignore/base.py
index 7373a4e..02cdb42 100644
--- a/pathspec/patterns/gitignore/base.py
+++ b/pathspec/patterns/gitignore/base.py
@@ -105,6 +105,14 @@ def escape(s: AnyStr) -> AnyStr:
 		# Reference: https://git-scm.com/docs/gitignore#_pattern_format
 		out_string = ''.join((f"\\{x}" if x in '\\[]!*#?' else x) for x in string)
 
+		# EDGE CASE: Git strips trailing spaces from a pattern unless they are
+		# escaped with a backslash. Escape them so an escaped filename that ends
+		# with a space still matches that file.
+		stripped = out_string.rstrip(' ')
+		trailing = len(out_string) - len(stripped)
+		if trailing:
+			out_string = stripped + '\\ ' * trailing
+
 		if return_type is bytes:
 			out_bytes = out_string.encode(_BYTES_ENCODING)
 			return out_bytes  # type: ignore[return-value]
diff --git a/tests/test_02_gitignore_base.py b/tests/test_02_gitignore_base.py
index f315194..3612b65 100644
--- a/tests/test_02_gitignore_base.py
+++ b/tests/test_02_gitignore_base.py
@@ -20,7 +20,7 @@ def test_01_escape_bytes(self):
 		Test escaping binary strings.
 		"""
 		byte_to_escaped = {__b: b'\\' + __b for __b in (
-			__c.encode(_BYTES_ENCODING) for __c in '\\[]!*#?'
+			__c.encode(_BYTES_ENCODING) for __c in '\\[]!*#? '
 		)}
 		for char_ord in range(256):
 			char_byte = chr(char_ord).encode(_BYTES_ENCODING)
@@ -32,7 +32,7 @@ def test_01_escape_str(self):
 		"""
 		Test escaping unicode strings.
 		"""
-		char_to_escaped = {__c: f"\\{__c}" for __c in '\\[]!*#?'}
+		char_to_escaped = {__c: f"\\{__c}" for __c in '\\[]!*#? '}
 		for char_ord in range(128):
 			char = chr(char_ord)
 			escape_val = _GitIgnoreBasePattern.escape(char)
diff --git a/tests/test_04_gitignore_spec.py b/tests/test_04_gitignore_spec.py
index 9851c60..618f658 100644
--- a/tests/test_04_gitignore_spec.py
+++ b/tests/test_04_gitignore_spec.py
@@ -621,6 +621,18 @@ def test_08_escape(self):
 		result = GitIgnoreSpecPattern.escape(fname)
 		self.assertEqual(result, escaped)
 
+	def test_08_escape_trailing_space(self):
+		"""
+		Test that escaping a filename with a trailing space keeps the space, so
+		the escaped pattern still matches the file. Git strips unescaped trailing
+		spaces from a pattern.
+		"""
+		for fname in ['foo ', 'trailing  ', ' ']:
+			escaped = GitIgnoreSpecPattern.escape(fname)
+			self.assertTrue(escaped.endswith('\\ '), (fname, escaped))
+			pattern = GitIgnoreSpecPattern(escaped)
+			self.assertEqual(set(filter(pattern.match_file, [fname])), {fname}, (fname, escaped))
+
 	def test_09_single_escape_fail(self):
 		"""
 		Test an escape on a line by itself.