Allow touching existing read-only files

newsfragments/+touch-readonly.bugfix.rst

@@ -0,0 +1 @@
+Allow ``Path.touch()`` to update timestamps on existing read-only files.

path/__init__.py

@@ -1415,8 +1415,7 @@ def touch(self) -> Self:
         """Set the access/modified times of this file to the current time.
         Create the file if it does not exist.
         """
-        os.close(os.open(self, os.O_WRONLY | os.O_CREAT, 0o666))
-        os.utime(self, None)
+        pathlib.Path(self).touch()
         return self
 
     def remove(self) -> Self:

tests/test_path.py

@@ -460,6 +460,20 @@ class TestScratchDir:
     Tests that run in a temporary directory (does not test TempDir class)
     """
 
+    @pytest.mark.skipif(os.name == 'nt', reason='POSIX file permissions')
+    def test_touch_readonly_file(self, tmp_path):
+        target = Path(tmp_path / 'readonly.txt')
+        target.write_text('preserved content')
+        target.utime((1_000_000_000, 1_000_000_000))
+        target.chmod(0o444)
+        try:
+            assert target.touch() is target
+            assert target.stat().st_mtime > 1_000_000_000
+            assert target.stat().st_mode & 0o777 == 0o444
+            assert target.read_text(encoding='utf-8') == 'preserved content'
+        finally:
+            target.chmod(0o644)
+
     def test_context_manager(self, tmpdir):
         """Can be used as context manager for chdir."""
         d = Path(tmpdir)