From 7654f41a8fe0e794c584e22434811898c81458af Mon Sep 17 00:00:00 2001
From: Sri Charan <cherukusricharanreddy@gmail.com>
Date: Wed, 7 Oct 2026 23:55:34 +0530
Subject: [PATCH] Fix fnmatch filtering under simulated Windows

---
 CHANGES.md                                  |  3 +++
 pyfakefs/fake_filesystem_unittest.py        |  5 +++++
 pyfakefs/tests/fake_filesystem_glob_test.py | 24 +++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/CHANGES.md b/CHANGES.md
index c40e7404..db2fb654 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -13,6 +13,9 @@ The released versions correspond to PyPI releases.
 
 ### Fixes
 
+* fixed `fnmatch.filter` and `glob.glob` missing uppercase names
+  when simulating Windows on a POSIX host
+  (see [#1345](https://github.com/pytest-dev/pyfakefs/issues/1345))
 * fixed a crash if the stack limit was set to a low value
   (see [#1313](https://github.com/pytest-dev/pyfakefs/issues/1313))
 * fixed `os.ftruncate` to inspect the `FakeFileWrapper` returned by
diff --git a/pyfakefs/fake_filesystem_unittest.py b/pyfakefs/fake_filesystem_unittest.py
index 22ce33d4..6a07d5be 100644
--- a/pyfakefs/fake_filesystem_unittest.py
+++ b/pyfakefs/fake_filesystem_unittest.py
@@ -38,6 +38,7 @@
 
 import _io  # type:ignore[import]
 import doctest
+import fnmatch
 import functools
 import genericpath
 import glob
@@ -1121,6 +1122,10 @@ def patch_modules(self) -> None:
         for name, modules in self.FS_MODULES.items():
             for module, attr in modules:
                 try:
+                    # fnmatch.filter skips normcase when os.path is posixpath.
+                    # The fake path module can use Windows case rules instead.
+                    if module is fnmatch and name == "posixpath":
+                        continue
                     if not skip_prefixes or not module.__name__.startswith(
                         skip_prefixes
                     ):
diff --git a/pyfakefs/tests/fake_filesystem_glob_test.py b/pyfakefs/tests/fake_filesystem_glob_test.py
index 3747e8af..5e604809 100644
--- a/pyfakefs/tests/fake_filesystem_glob_test.py
+++ b/pyfakefs/tests/fake_filesystem_glob_test.py
@@ -15,12 +15,14 @@
 """Test for glob using fake_filesystem."""
 
 import contextlib
+import fnmatch
 import glob
 import os
 import sys
 import unittest
 
 from pyfakefs import fake_filesystem_unittest
+from pyfakefs.fake_filesystem import OSType
 
 
 class FakeGlobUnitTest(fake_filesystem_unittest.TestCase):
@@ -86,6 +88,28 @@ def test_has_magic(self):
         self.assertTrue(glob.has_magic("["))
         self.assertFalse(glob.has_magic("a"))
 
+    def test_fnmatch_filter_windows(self):
+        self.fs.os = OSType.WINDOWS
+        for pattern in ("*.txt", "*.TXT"):
+            with self.subTest(pattern=pattern):
+                self.assertEqual(
+                    ["B.TXT"], fnmatch.filter(["B.TXT", "other.log"], pattern)
+                )
+                self.assertEqual(
+                    [b"B.TXT"],
+                    fnmatch.filter([b"B.TXT", b"other.log"], pattern.encode()),
+                )
+
+    def test_glob_windows_case_insensitive(self):
+        self.fs.os = OSType.WINDOWS
+        self.fs.create_file(r"C:\d\B.TXT")
+        self.assertEqual([r"C:\d\B.TXT"], glob.glob(r"C:\d\*.txt"))
+
+    def test_fnmatch_filter_linux_case_sensitive(self):
+        self.fs.os = OSType.LINUX
+        self.assertEqual([], fnmatch.filter(["B.TXT"], "*.txt"))
+        self.assertEqual(["B.TXT"], fnmatch.filter(["B.TXT"], "*.TXT"))
+
 
 if __name__ == "__main__":
     unittest.main()