Performance: do not reload tempfile

- patch tempfile instead directly (Posix only)
- decrease allowed time for performance tests

Author: mrbean-bremen

CHANGES.md

@@ -14,6 +14,9 @@ The released versions correspond to PyPI releases.
 
 ## Unreleased
 
+### Performance
+* avoid reloading `tempfile` in Posix systems
+
 ### Infrastructure
 * use trusted publisher for release (see https://docs.pypi.org/trusted-publishers/)
 
@@ -33,7 +36,9 @@ Adds official Python 3.13 support, improves OS emulation behavior.
 * the `additional_skip_names` parameter now works with more modules (see [#1023](../../issues/1023))
 * added support for `os.fchmod`, allow file descriptor argument for `os.chmod` only for POSIX
   for Python < 3.13
-* avoid reloading `glob` in Python 3.13 (did affect test performance)
+
+### Performance
+* avoid reloading `glob` in Python 3.13
 
 ### Fixes
 * removing files while iterating over `scandir` results is now possible (see [#1051](../../issues/1051))
@@ -574,6 +579,8 @@ release.
     default to avoid a large performance impact. An additional parameter
     `patch_default_args` has been added that switches this behavior on
     (see [#567](../../issues/567)).
+
+### Performance
   * Added performance improvements in the test setup, including caching the
     unpatched modules
 

pyfakefs/fake_filesystem_unittest.py

@@ -95,6 +95,41 @@
 PATH_MODULE = "ntpath" if sys.platform == "win32" else "posixpath"
 
 
+class TempfilePatcher:
+    """Handles tempfile patching for Posix systems."""
+
+    def __init__(self):
+        self.tempfile_cleanup = None
+
+    def start_patching(self):
+        if self.tempfile_cleanup is not None:
+            return
+        if sys.version_info >= (3, 12):
+
+            def cleanup(self_, windows=(os.name == "nt"), unlink=None):
+                self.tempfile_cleanup(self_, windows, unlink or os.unlink)
+
+            self.tempfile_cleanup = tempfile._TemporaryFileCloser.cleanup  # type: ignore[module-attr]
+            tempfile._TemporaryFileCloser.cleanup = cleanup  # type: ignore[module-attr]
+        elif sys.platform != "win32":
+
+            def close(self_, unlink=None):
+                self.tempfile_cleanup(self_, unlink or os.unlink)
+
+            self.tempfile_cleanup = tempfile._TemporaryFileCloser.close  # type: ignore[module-attr]
+            tempfile._TemporaryFileCloser.close = close  # type: ignore[module-attr]
+
+    def stop_patching(self):
+        if self.tempfile_cleanup is None:
+            return
+        if sys.version_info < (3, 12):
+            tempfile._TemporaryFileCloser.close = self.tempfile_cleanup  # type: ignore[module-attr]
+        else:
+            tempfile._TemporaryFileCloser.cleanup = self.tempfile_cleanup  # type: ignore[module-attr]
+        # reset the cached tempdir in tempfile
+        tempfile.tempdir = None
+
+
 def patchfs(
     _func: Optional[Callable] = None,
     *,
@@ -576,6 +611,7 @@ def __init__(
         self.patch_open_code = patch_open_code
         self.linecache_updatecache = None
         self.linecache_checkcache = None
+        self.tempfile_patcher = TempfilePatcher()
 
         if additional_skip_names is not None:
             skip_names = [
@@ -590,9 +626,7 @@ def __init__(
         self._init_fake_module_classes()
 
         # reload tempfile under posix to patch default argument
-        self.modules_to_reload: List[ModuleType] = (
-            [] if sys.platform == "win32" else [tempfile]
-        )
+        self.modules_to_reload: List[ModuleType] = []
         if modules_to_reload is not None:
             self.modules_to_reload.extend(modules_to_reload)
         self.patch_default_args = patch_default_args
@@ -977,6 +1011,8 @@ def start_patching(self) -> None:
                 self.linecache_checkcache = linecache.checkcache
                 linecache.checkcache = self.checkcache
 
+            self.tempfile_patcher.start_patching()
+
             self.patch_modules()
             self.patch_functions()
             self.patch_defaults()
@@ -1075,6 +1111,7 @@ def stop_patching(self, temporary=False) -> None:
             if self.use_dynamic_patch and self._dyn_patcher:
                 self._dyn_patcher.cleanup()
                 sys.meta_path.pop(0)
+            self.tempfile_patcher.stop_patching()
             if self.linecache_updatecache is not None:
                 linecache.updatecache = self.linecache_updatecache
                 linecache.checkcache = self.linecache_checkcache

pyfakefs/tests/fake_filesystem_unittest_test.py

@@ -541,25 +541,20 @@ def test_non_root_behavior(self):
 
 class PauseResumeTest(fake_filesystem_unittest.TestCase):
     def setUp(self):
-        self.real_temp_file = None
         self.setUpPyfakefs()
 
-    def tearDown(self):
-        if self.real_temp_file is not None:
-            self.real_temp_file.close()
-
     def test_pause_resume(self):
         fake_temp_file = tempfile.NamedTemporaryFile()
         self.assertTrue(self.fs.exists(fake_temp_file.name))
         self.assertTrue(os.path.exists(fake_temp_file.name))
         self.pause()
         self.assertTrue(self.fs.exists(fake_temp_file.name))
         self.assertFalse(os.path.exists(fake_temp_file.name))
-        self.real_temp_file = tempfile.NamedTemporaryFile()
-        self.assertFalse(self.fs.exists(self.real_temp_file.name))
-        self.assertTrue(os.path.exists(self.real_temp_file.name))
+        real_temp_file = tempfile.NamedTemporaryFile()
+        self.assertFalse(self.fs.exists(real_temp_file.name))
+        self.assertTrue(os.path.exists(real_temp_file.name))
         self.resume()
-        self.assertFalse(os.path.exists(self.real_temp_file.name))
+        self.assertFalse(os.path.exists(real_temp_file.name))
         self.assertTrue(os.path.exists(fake_temp_file.name))
 
     def test_pause_resume_fs(self):
@@ -572,15 +567,15 @@ def test_pause_resume_fs(self):
         self.fs.pause()
         self.assertTrue(self.fs.exists(fake_temp_file.name))
         self.assertFalse(os.path.exists(fake_temp_file.name))
-        self.real_temp_file = tempfile.NamedTemporaryFile()
-        self.assertFalse(self.fs.exists(self.real_temp_file.name))
-        self.assertTrue(os.path.exists(self.real_temp_file.name))
+        real_temp_file = tempfile.NamedTemporaryFile()
+        self.assertFalse(self.fs.exists(real_temp_file.name))
+        self.assertTrue(os.path.exists(real_temp_file.name))
         # pause does nothing if already paused
         self.fs.pause()
-        self.assertFalse(self.fs.exists(self.real_temp_file.name))
-        self.assertTrue(os.path.exists(self.real_temp_file.name))
+        self.assertFalse(self.fs.exists(real_temp_file.name))
+        self.assertTrue(os.path.exists(real_temp_file.name))
         self.fs.resume()
-        self.assertFalse(os.path.exists(self.real_temp_file.name))
+        self.assertFalse(os.path.exists(real_temp_file.name))
         self.assertTrue(os.path.exists(fake_temp_file.name))
 
     def test_pause_resume_contextmanager(self):
@@ -590,10 +585,10 @@ def test_pause_resume_contextmanager(self):
         with Pause(self):
             self.assertTrue(self.fs.exists(fake_temp_file.name))
             self.assertFalse(os.path.exists(fake_temp_file.name))
-            self.real_temp_file = tempfile.NamedTemporaryFile()
-            self.assertFalse(self.fs.exists(self.real_temp_file.name))
-            self.assertTrue(os.path.exists(self.real_temp_file.name))
-        self.assertFalse(os.path.exists(self.real_temp_file.name))
+            real_temp_file = tempfile.NamedTemporaryFile()
+            self.assertFalse(self.fs.exists(real_temp_file.name))
+            self.assertTrue(os.path.exists(real_temp_file.name))
+        self.assertFalse(os.path.exists(real_temp_file.name))
         self.assertTrue(os.path.exists(fake_temp_file.name))
 
     def test_pause_resume_fs_contextmanager(self):
@@ -603,10 +598,10 @@ def test_pause_resume_fs_contextmanager(self):
         with Pause(self.fs):
             self.assertTrue(self.fs.exists(fake_temp_file.name))
             self.assertFalse(os.path.exists(fake_temp_file.name))
-            self.real_temp_file = tempfile.NamedTemporaryFile()
-            self.assertFalse(self.fs.exists(self.real_temp_file.name))
-            self.assertTrue(os.path.exists(self.real_temp_file.name))
-        self.assertFalse(os.path.exists(self.real_temp_file.name))
+            real_temp_file = tempfile.NamedTemporaryFile()
+            self.assertFalse(self.fs.exists(real_temp_file.name))
+            self.assertTrue(os.path.exists(real_temp_file.name))
+        self.assertFalse(os.path.exists(real_temp_file.name))
         self.assertTrue(os.path.exists(fake_temp_file.name))
 
     def test_pause_resume_without_patcher(self):

pyfakefs/tests/performance_test.py

@@ -61,10 +61,10 @@ class TimePerformanceTest(TestCase):
         """
 
         def test_cached_time(self):
-            self.assertLess(SetupPerformanceTest.elapsed_time, 0.4)
+            self.assertLess(SetupPerformanceTest.elapsed_time, 0.18)
 
         def test_uncached_time(self):
-            self.assertLess(SetupNoCachePerformanceTest.elapsed_time, 6)
+            self.assertLess(SetupNoCachePerformanceTest.elapsed_time, 4)
 
     def test_setup(self):
         pass