[fix] Fixes a bug that caused internal pytest errors during test coll…

…ection with doctests.

Pytest-asyncio attaches an event loop of a particular scope to each collector during pytest_collectstart. The implementation did not account for the fact that collectors may have specialized subclasses, such as DoctestModule. This caused a KeyError during a dictionary access, leading to an internal pytest error in the collection phase.

This patch changes the implementation of pytest_collectstart to account for subclasses of collectors.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

pytest_asyncio/plugin.py

@@ -544,25 +544,33 @@ def pytest_pycollect_makeitem_convert_async_functions_to_subclass(
 _event_loop_fixture_id = StashKey[str]
 _fixture_scope_by_collector_type = {
     Class: "class",
-    Module: "module",
+    # Package is a subclass of module and the dict is used in isinstance checks
+    # Therefore, the order matters and Package needs to appear before Module
     Package: "package",
+    Module: "module",
     Session: "session",
 }
 
 
 @pytest.hookimpl
 def pytest_collectstart(collector: pytest.Collector):
+    try:
+        collector_scope = next(
+            scope
+            for cls, scope in _fixture_scope_by_collector_type.items()
+            if isinstance(collector, cls)
+        )
+    except StopIteration:
+        return
     # Session is not a PyCollector type, so it doesn't have a corresponding
     # "obj" attribute to attach a dynamic fixture function to.
     # However, there's only one session per pytest run, so there's no need to
     # create the fixture dynamically. We can simply define a session-scoped
     # event loop fixture once in the plugin code.
-    if isinstance(collector, Session):
+    if collector_scope == "session":
         event_loop_fixture_id = _session_event_loop.__name__
         collector.stash[_event_loop_fixture_id] = event_loop_fixture_id
         return
-    if not isinstance(collector, (Class, Module, Package)):
-        return
     # There seem to be issues when a fixture is shadowed by another fixture
     # and both differ in their params.
     # https://github.com/pytest-dev/pytest/issues/2043
@@ -574,7 +582,7 @@ def pytest_collectstart(collector: pytest.Collector):
     collector.stash[_event_loop_fixture_id] = event_loop_fixture_id
 
     @pytest.fixture(
-        scope=_fixture_scope_by_collector_type[type(collector)],
+        scope=collector_scope,
         name=event_loop_fixture_id,
     )
     def scoped_event_loop(

tests/test_doctest.py

@@ -0,0 +1,19 @@
+from textwrap import dedent
+
+from pytest import Pytester
+
+
+def test_plugin_does_not_interfere_with_doctest_collection(pytester: Pytester):
+    pytester.makepyfile(
+        dedent(
+            '''\
+            def any_function():
+                """
+                >>> 42
+                42
+                """
+            '''
+        ),
+    )
+    result = pytester.runpytest("--asyncio-mode=strict", "--doctest-modules")
+    result.assert_outcomes(passed=1)