Overwrite instance check for PathLibPathModule

- fixes pytest-dev#666 without the need to skip _pytest.pathlib patching
- add module and session scoped fs fixtures
- fixes pytest-dev#684

CHANGES.md

@@ -18,6 +18,14 @@ The released versions correspond to PyPi releases.
 ### New Features
 * added some support for the upcoming Python version 3.11
   (see [#677](../../issues/677))
+* added convenience fixtures for module- and session based `fs` fixtures
+  (`fs_module` and `fs_session`)
+
+### Fixes
+* fixed an incompatibility of `tmpdir` (and probably other fixtures) with the 
+  module-scoped version of `fs`; had been introduced in 
+  pyfakefs 4.5.5 by the fix for [#666](../../issues/666)
+  (see [#684](../../issues/684))
 
 ## [Version 4.5.6](https://pypi.python.org/pypi/pyfakefs/4.5.6) (2022-03-17)
 Fixes a regression which broke tests with older pytest versions (< 3.9).

pyfakefs/fake_pathlib.py

@@ -792,6 +792,11 @@ def __call__(self, *args, **kwargs):
     def __getattr__(self, name):
         return getattr(self.fake_pathlib.Path, name)
 
+    @classmethod
+    def __instancecheck__(cls, instance):
+        # fake the inheritance to pass isinstance checks - see #666
+        return isinstance(instance, PurePath)
+
 
 class RealPath(pathlib.Path):
     """Replacement for `pathlib.Path` if it shall not be faked.

pyfakefs/pytest_plugin.py

@@ -8,16 +8,13 @@ def my_fakefs_test(fs):
     fs.create_file('/var/data/xx1.txt')
     assert os.path.exists('/var/data/xx1.txt')
 """
-import _pytest
 import py
 import pytest
 
 from pyfakefs.fake_filesystem_unittest import Patcher
 
 Patcher.SKIPMODULES.add(py)
 Patcher.SKIPMODULES.add(pytest)
-if hasattr(_pytest, "pathlib"):
-    Patcher.SKIPMODULES.add(_pytest.pathlib)
 
 
 @pytest.fixture
@@ -31,3 +28,27 @@ def fs(request):
     patcher.setUp()
     yield patcher.fs
     patcher.tearDown()
+
+
+@pytest.fixture(scope="module")
+def fs_module(request):
+    """ Module-scoped fake filesystem fixture. """
+    if hasattr(request, 'param'):
+        patcher = Patcher(*request.param)
+    else:
+        patcher = Patcher()
+    patcher.setUp()
+    yield patcher.fs
+    patcher.tearDown()
+
+
+@pytest.fixture(scope="session")
+def fs_session(request):
+    """ Session-scoped fake filesystem fixture. """
+    if hasattr(request, 'param'):
+        patcher = Patcher(*request.param)
+    else:
+        patcher = Patcher()
+    patcher.setUp()
+    yield patcher.fs
+    patcher.tearDown()

pyfakefs/tests/fake_filesystem_unittest_test.py

@@ -32,6 +32,8 @@
 from pathlib import Path
 from unittest import TestCase, mock
 
+import pytest
+
 import pyfakefs.tests.import_as_example
 import pyfakefs.tests.logsio
 from pyfakefs import fake_filesystem_unittest, fake_filesystem
@@ -879,5 +881,15 @@ def test_is_absolute(self, fs):
         self.assertTrue(pathlib.Path(".").absolute().is_absolute())
 
 
+class TestModuleScopedFsWithTmpdir:
+    @pytest.fixture(autouse=True)
+    def test_internal(self, tmpdir):
+        yield
+
+    def test_fail(self, fs_module):
+        # Regression test for #684
+        assert True
+
+
 if __name__ == "__main__":
     unittest.main()