Support modules instead of module names in additional_skip_names

- closes #482

CHANGES.md

@@ -7,6 +7,8 @@ The release versions are PyPi releases.
   * removed unneeded parameter `use_dynamic_patch`
 
 #### New Features
+  * added possibility to use modules instead of module names for the
+    `additional_skip_names` argument (see [#482](../../issues/482))
   * added argument `allow_root_user` to `Patcher` and `UnitTest` to allow
     forcing non-root access (see [#474](../../issues/474))
   * added basic support for `os.pipe` (see [#473](../../issues/473))

docs/usage.rst

@@ -290,11 +290,18 @@ offending module to ``additional_skip_names``:
   with Patcher(additional_skip_names=['pydevd']) as patcher:
       patcher.fs.create_file('foo')
 
+Alternatively to the module names, the modules themselves may be used:
+
+.. code:: python
+
+  import pydevd
+
+  with Patcher(additional_skip_names=[pydevd]) as patcher:
+      patcher.fs.create_file('foo')
+
 There is also the global variable ``Patcher.SKIPNAMES`` that can be extended
 for that purpose, though this seldom shall be needed (except for own pytest
-plugins, as shown in the example mentioned above). Other than in
-``additional_skip_names``, which is a list of modules names, this is a list
-of modules that have to be imported before.
+plugins, as shown in the example mentioned above).
 
 allow_root_user
 ~~~~~~~~~~~~~~~

pyfakefs/fake_filesystem_unittest.py

@@ -120,6 +120,7 @@ class TestCaseMixin(object):
         additional_skip_names: names of modules inside of which no module
             replacement shall be performed, in addition to the names in
             :py:attr:`fake_filesystem_unittest.Patcher.SKIPNAMES`.
+            Instead of the module names, the modules themselves may be used.
         modules_to_reload: A list of modules that need to be reloaded
             to be patched dynamically; may be needed if the module
             imports file system modules under an alias
@@ -328,7 +329,9 @@ def __init__(self, additional_skip_names=None,
         self.fake_open = None
 
         if additional_skip_names is not None:
-            self._skipNames.update(additional_skip_names)
+            skip_names = [m.__name__ if inspect.ismodule(m) else m
+                          for m in additional_skip_names]
+            self._skipNames.update(skip_names)
 
         self.modules_to_reload = [tempfile]
         if modules_to_reload is not None:

pyfakefs/tests/fake_filesystem_unittest_test.py

@@ -265,6 +265,41 @@ def test_path_exists(self):
             pyfakefs.tests.import_as_example.check_if_exists4(file_path))
 
 
+class NoSkipNamesTest(fake_filesystem_unittest.TestCase):
+    """Reference test for additional_skip_names tests:
+     make sure that the module is patched by default."""
+
+    def test_path_exists(self):
+        self.assertTrue(
+            pyfakefs.tests.import_as_example.exists_this_file())
+
+
+class AdditionalSkipNamesTest(fake_filesystem_unittest.TestCase):
+    """Make sure that modules in additional_skip_names are not patched.
+    Passes module name to `additional_skip_names`."""
+
+    def setUp(self):
+        self.setUpPyfakefs(
+            additional_skip_names=['pyfakefs.tests.import_as_example'])
+
+    def test_path_exists(self):
+        self.assertFalse(
+            pyfakefs.tests.import_as_example.exists_this_file())
+
+
+class AdditionalSkipNamesModuleTest(fake_filesystem_unittest.TestCase):
+    """Make sure that modules in additional_skip_names are not patched.
+    Passes module to `additional_skip_names`."""
+
+    def setUp(self):
+        self.setUpPyfakefs(
+            additional_skip_names=[pyfakefs.tests.import_as_example])
+
+    def test_path_exists(self):
+        self.assertFalse(
+            pyfakefs.tests.import_as_example.exists_this_file())
+
+
 class FakeExampleModule(object):
     """Used to patch a function that uses system-specific functions that
     cannot be patched automatically."""

pyfakefs/tests/import_as_example.py

@@ -95,3 +95,8 @@ def file_contents1(filepath):
 def file_contents2(filepath):
     with io_open(filepath) as f:
         return f.read()
+
+
+def exists_this_file():
+    "Returns True in real fs only"
+    return exists(__file__)