ansible-test - Support pylint assertion rewriting (#80020)

Add support for `pylint` assertion rewriting when running unit tests on Python 3.5 and later.

changelogs/fragments/ansible-test-pytest-assertion-rewriting.yml

@@ -0,0 +1,5 @@
+bugfixes:
+  - ansible-test - Add support for ``pylint`` assertion rewriting when running unit tests on Python 3.5 and later.
+                   Resolves issue https://github.com/ansible/ansible/issues/68032
+known_issues:
+  - ansible-test - Unit tests for collections do not support ``pylint`` assertion rewriting on Python 2.7.

test/integration/targets/ansible-test-units-assertions/aliases

@@ -0,0 +1,4 @@
+shippable/generic/group1  # runs in the default test container
+context/controller
+needs/target/collection
+needs/target/ansible-test

test/integration/targets/ansible-test-units-assertions/ansible_collections/ns/col/tests/unit/plugins/modules/test_assertion.py

@@ -0,0 +1,6 @@
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+
+def test_assertion():
+    assert dict(yes=True) == dict(no=False)

test/integration/targets/ansible-test-units-assertions/runme.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+source ../collection/setup.sh
+
+set -x
+
+options=$("${TEST_DIR}"/../ansible-test/venv-pythons.py --only-versions)
+IFS=', ' read -r -a pythons <<< "${options}"
+
+for python in "${pythons[@]}"; do
+  if ansible-test units --color --truncate 0 --python "${python}" --requirements "${@}" 2>&1 | tee pylint.log; then
+    echo "Test did not fail as expected."
+    exit 1
+  fi
+
+  if [ "${python}" = "2.7" ]; then
+    grep "^E  *AssertionError$" pylint.log
+  else
+
+    grep "^E  *AssertionError: assert {'yes': True} == {'no': False}$" pylint.log
+  fi
+done

test/integration/targets/ansible-test/venv-pythons.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 """Return target Python options for use with ansible-test."""
 
+import argparse
 import os
 import shutil
 import subprocess
@@ -10,6 +11,11 @@ from ansible import release
 
 
 def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--only-versions', action='store_true')
+
+    options = parser.parse_args()
+
     ansible_root = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(release.__file__))))
     source_root = os.path.join(ansible_root, 'test', 'lib')
 
@@ -33,6 +39,10 @@ def main():
             print(f'{executable} - {"fail" if process.returncode else "pass"}', file=sys.stderr)
 
             if not process.returncode:
+                if options.only_versions:
+                    args.append(python_version)
+                    continue
+
                 args.extend(['--target-python', f'venv/{python_version}'])
 
     print(' '.join(args))

test/lib/ansible_test/_util/target/pytest/plugins/ansible_pytest_collections.py

@@ -32,6 +32,50 @@ def collection_pypkgpath(self):
     raise Exception('File "%s" not found in collection path "%s".' % (self.strpath, ANSIBLE_COLLECTIONS_PATH))
 
 
+def enable_assertion_rewriting_hook():  # type: () -> None
+    """
+    Enable pylint's AssertionRewritingHook on Python 3.x.
+    This is necessary because the Ansible collection loader intercepts imports before the pylint provided loader ever sees them.
+    """
+    import sys
+
+    if sys.version_info[0] == 2:
+        return  # Python 2.x is not supported
+
+    hook_name = '_pytest.assertion.rewrite.AssertionRewritingHook'
+    hooks = [hook for hook in sys.meta_path if hook.__class__.__module__ + '.' + hook.__class__.__qualname__ == hook_name]
+
+    if len(hooks) != 1:
+        raise Exception('Found {} instance(s) of "{}" in sys.meta_path.'.format(len(hooks), hook_name))
+
+    assertion_rewriting_hook = hooks[0]
+
+    # This is based on `_AnsibleCollectionPkgLoaderBase.exec_module` from `ansible/utils/collection_loader/_collection_finder.py`.
+    def exec_module(self, module):
+        # short-circuit redirect; avoid reinitializing existing modules
+        if self._redirect_module:  # pylint: disable=protected-access
+            return
+
+        # execute the module's code in its namespace
+        code_obj = self.get_code(self._fullname)  # pylint: disable=protected-access
+
+        if code_obj is not None:  # things like NS packages that can't have code on disk will return None
+            # This logic is loosely based on `AssertionRewritingHook._should_rewrite` from pytest.
+            # See: https://github.com/pytest-dev/pytest/blob/779a87aada33af444f14841a04344016a087669e/src/_pytest/assertion/rewrite.py#L209
+            should_rewrite = self._package_to_load == 'conftest' or self._package_to_load.startswith('test_')  # pylint: disable=protected-access
+
+            if should_rewrite:
+                # noinspection PyUnresolvedReferences
+                assertion_rewriting_hook.exec_module(module)
+            else:
+                exec(code_obj, module.__dict__)  # pylint: disable=exec-used
+
+    # noinspection PyProtectedMember
+    from ansible.utils.collection_loader._collection_finder import _AnsibleCollectionPkgLoaderBase
+
+    _AnsibleCollectionPkgLoaderBase.exec_module = exec_module
+
+
 def pytest_configure():
     """Configure this pytest plugin."""
     try:
@@ -40,6 +84,8 @@ def pytest_configure():
     except AttributeError:
         pytest_configure.executed = True
 
+    enable_assertion_rewriting_hook()
+
     # noinspection PyProtectedMember
     from ansible.utils.collection_loader._collection_finder import _AnsibleCollectionFinder