#10 unload modules imported by pytest

Author: reverbc

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
 ## [Unreleased]
+### Fixed
+- Fix pytest **Module already imported so cannot be rewritten** warning when the package being linted was used by pytest/conftest already (#10)
 
 ## [1.0.1] - 2021-03-03
 ### Added

pylint_pytest/checkers/fixture.py

@@ -72,13 +72,25 @@ def visit_module(self, node):
                 # run pytest session with customized plugin to collect fixtures
                 fixture_collector = FixtureCollector()
 
+                # save and remove modules imported by pytest to prevent pytest warning during fixture collection:
+                # <PytestAssertRewriteWarning: Module already imported so cannot be rewritten>
+                sys_mods = set(sys.modules.keys())
+
                 # save and restore sys.path to prevent pytest.main from altering it
                 sys_path = sys.path.copy()
+
                 pytest.main(
                     [node.file, '--fixtures', '--collect-only'],
                     plugins=[fixture_collector],
                 )
+
+                # restore sys.path
                 sys.path = sys_path
+
+                # unload modules imported by pytest.main
+                for module in set(sys.modules.keys()) - sys_mods:
+                    del sys.modules[module]
+
                 FixtureChecker._pytest_fixtures = fixture_collector.fixtures
         finally:
             # restore output devices