Merge "Add H216 to flag use of third party mock"

HACKING.rst

@@ -361,6 +361,24 @@ exception possible should be used.
   assertEqual(A in B, False) or assertEqual(False, A in B) to the more
   specific assertIn/NotIn(A, B)
 
+- [H216] Make sure unittest.mock is used instead of the third party mock
+  library. On by default.
+
+  Starting with Python 3.3 and later, the mock module was added under unittest.
+  Previously, this functionality was only available by using the third party
+  ``mock`` library.
+
+  Most users are not aware of this subtle distinction. This results in issues
+  where the project does not declare the ``mock`` library in its requirements
+  file, but the code does an ``import mock`` assuming that the module is
+  present. This may work initially if one of the project's dependencies ends up
+  pulling that dependency in indirectly, but then can cause things to suddenly
+  break if that transitive dependency goes away.
+
+  Since this third party library usage is done without being aware of it, this
+  check is enabled by default to make sure those projects that actually do
+  intend to use the ``mock`` library are doing so explicitly.
+
 OpenStack Trademark
 -------------------
 

hacking/checks/mock_checks.py

@@ -11,6 +11,7 @@
 #  under the License.
 
 import ast
+import re
 
 from hacking import core
 
@@ -139,3 +140,37 @@ class FunctionNameFinder(ast.NodeVisitor):
         if isinstance(node, ast.Call):
             return super(FunctionNameFinder, self).visit(node.func)
         return super(FunctionNameFinder, self).visit(node)
+
+
+third_party_mock = re.compile('^import.mock')
+from_third_party_mock = re.compile('^from.mock.import')
+
+
+@core.flake8ext
+def hacking_no_third_party_mock(logical_line, noqa):
+    """Check for use of mock instead of unittest.mock.
+
+    Projects have had issues with using mock without including it in their
+    requirements, thinking it is the standard library version. This makes it so
+    these projects need to explicitly turn off this check to make it clear they
+    intended to use it.
+
+    Okay: from unittest import mock
+    Okay: from unittest.mock import patch
+    Okay: import unittest.mock
+    H216: import mock
+    H216: from mock import patch
+    Okay: try: import mock
+    Okay: import mock  # noqa
+    """
+    msg = ('H216: The unittest.mock module should be used rather than the '
+           'third party mock package unless actually needed. If so, disable '
+           'the H216 check in hacking config and ensure mock is declared in '
+           "the project's requirements.")
+
+    if noqa:
+        return
+
+    if (re.match(third_party_mock, logical_line) or
+            re.match(from_third_party_mock, logical_line)):
+        yield (0, msg)

hacking/tests/checks/test_except_checks.py

@@ -12,8 +12,8 @@
 # limitations under the License.
 
 import textwrap
+from unittest import mock
 
-import mock
 import pycodestyle
 
 from hacking.checks import except_checks

hacking/tests/checks/test_mock.py

@@ -0,0 +1,37 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import ddt
+
+from hacking.checks import mock_checks
+from hacking import tests
+
+
+@ddt.ddt
+class MockingTestCase(tests.TestCase):
+    """This tests hacking checks related to the use of mocking."""
+
+    @ddt.unpack
+    @ddt.data(
+        (1, 'import mock', None),
+        (0, 'from unittest import mock', None),
+        (1, 'from mock import patch', None),
+        (0, 'from unittest.mock import patch', None),
+        (0, 'from mock', '# noqa'))
+    def test_H216_hacking_no_third_party_mock(self, err_count, line, noqa):
+        if err_count > 0:
+            self.assertCheckFails(mock_checks.hacking_no_third_party_mock,
+                                  line, noqa)
+        else:
+            self.assertCheckPasses(mock_checks.hacking_no_third_party_mock,
+                                   line, noqa)

lower-constraints.txt

@@ -12,7 +12,6 @@ Jinja2==2.10
 linecache2==1.0.0
 MarkupSafe==1.0
 mccabe==0.6.0
-mock==3.0.0
 pycodestyle==2.4.0
 pyflakes==2.1.1
 Pygments==2.2.0

setup.cfg

@@ -45,6 +45,7 @@ flake8.extension =
     H213 = hacking.checks.except_checks:hacking_assert_raises_regexp
     H214 = hacking.checks.except_checks:hacking_assert_true_or_false_with_in
     H215 = hacking.checks.except_checks:hacking_assert_equal_in
+    H216 = hacking.checks.mock_checks:hacking_no_third_party_mock
     H231 = hacking.checks.python23:hacking_python3x_except_compatible
     H232 = hacking.checks.python23:hacking_python3x_octal_literals
     H233 = hacking.checks.python23:hacking_python3x_print_function

test-requirements.txt

@@ -3,7 +3,6 @@
 # process, which may cause wedges in the gate later.
 coverage!=4.4,>=4.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
-mock>=3.0.0 # BSD
 python-subunit>=1.0.0 # Apache-2.0/BSD
 stestr>=2.0.0 # Apache-2.0
 testscenarios>=0.4 # Apache-2.0/BSD