Do not skip filesystem modules by name

- allows using own modules with the same name
- fixes #708

3 files changed, 43 insertions, 5 deletions

diff --git a/pyfakefs/fake_filesystem_unittest.py b/pyfakefs/fake_filesystem_unittest.py
index aaebc64..6d62ac0 100644
--- a/pyfakefs/fake_filesystem_unittest.py
+++ b/pyfakefs/fake_filesystem_unittest.py
@@ -35,10 +35,14 @@ Existing unit tests that use the real file system can be retrofitted to use
 pyfakefs by simply changing their base class from `:py:class`unittest.TestCase`
 to `:py:class`pyfakefs.fake_filesystem_unittest.TestCase`.
 """
+import _io  # type:ignore [import]
 import doctest
 import functools
+import genericpath
 import inspect
+import io
 import linecache
+import os
 import shutil
 import sys
 import tempfile
@@ -366,8 +370,6 @@ class Patcher:
     '''Stub nothing that is imported within these modules.
     `sys` is included to prevent `sys.path` from being stubbed with the fake
     `os.path`.
-    The `pytest` and `py` modules are used by pytest and have to access the
-    real file system.
     The `linecache` module is used to read the test file in case of test
     failure to get traceback information before test tear down.
     In order to make sure that reading the test file is not faked,
@@ -376,8 +378,21 @@ class Patcher:
     '''
     SKIPMODULES = {
         None, fake_filesystem, fake_filesystem_shutil,
-        sys, linecache, tokenize
+        sys, linecache, tokenize, os, io, _io, genericpath, os.path
     }
+    if sys.platform == 'win32':
+        import nt  # type:ignore [import]
+        import ntpath
+        SKIPMODULES.add(nt)
+        SKIPMODULES.add(ntpath)
+    else:
+        import posix
+        import posixpath
+        import fcntl
+        SKIPMODULES.add(posix)
+        SKIPMODULES.add(posixpath)
+        SKIPMODULES.add(fcntl)
+
     # caches all modules that do not have file system modules or function
     # to speed up _find_modules
     CACHED_MODULES: Set[ModuleType] = set()
@@ -391,8 +406,7 @@ class Patcher:
 
     IS_WINDOWS = sys.platform in ('win32', 'cygwin')
 
-    SKIPNAMES = {'os', 'path', 'io', 'genericpath', 'fcntl',
-                 OS_MODULE, PATH_MODULE}
+    SKIPNAMES: Set[str] = set()
 
     # hold values from last call - if changed, the cache has to be invalidated
     PATCHED_MODULE_NAMES: Set[str] = set()
diff --git a/pyfakefs/pytest_tests/io.py b/pyfakefs/pytest_tests/io.py
new file mode 100644
index 0000000..5d622f1
--- /dev/null
+++ b/pyfakefs/pytest_tests/io.py
@@ -0,0 +1,14 @@
+"""
+This is a test case for pyfakefs issue #708.
+It tests the usage of an own module with the same name as a patched filesystem
+module, the content is taken from the issue.
+"""
+
+
+class InputStream:
+    def __init__(self, name):
+        self.name = name
+
+    def read(self):
+        with open(self.name, 'r') as f:
+            return f.readline()
diff --git a/pyfakefs/pytest_tests/pytest_plugin_test.py b/pyfakefs/pytest_tests/pytest_plugin_test.py
index 5632ff6..04741f6 100644
--- a/pyfakefs/pytest_tests/pytest_plugin_test.py
+++ b/pyfakefs/pytest_tests/pytest_plugin_test.py
@@ -3,6 +3,7 @@ import os
 import tempfile
 
 from pyfakefs.fake_filesystem_unittest import Pause
+import pyfakefs.pytest_tests.io
 
 
 def test_fs_fixture(fs):
@@ -50,3 +51,12 @@ def test_pause_resume_contextmanager(fs):
         assert os.path.exists(real_temp_file.name)
     assert not os.path.exists(real_temp_file.name)
     assert os.path.exists(fake_temp_file.name)
+
+
+def test_use_own_io_module(fs):
+    filepath = 'foo.txt'
+    with open(filepath, 'w') as f:
+        f.write('bar')
+
+    stream = pyfakefs.pytest_tests.io.InputStream(filepath)
+    assert stream.read() == 'bar'