[refactor] Attach package-scoped fixtures to a virtual/temporary Python module in the package, rather than attaching the fixture to the package's __init__.py.

Signed-off-by: Michael Seifert <[email protected]>

Author: seifertm

pytest_asyncio/plugin.py

@@ -8,6 +8,8 @@
 import sys
 import warnings
 from asyncio import AbstractEventLoopPolicy
+from pathlib import Path
+from tempfile import NamedTemporaryFile
 from textwrap import dedent
 from typing import (
     Any,
@@ -625,18 +627,67 @@ def _patched_collect():
     elif type(collector) is Package:
 
         def _patched_collect():
-            # When collector is a package, collector.obj is the package's __init__.py.
-            # pytest doesn't seem to collect fixtures in __init__.py.
-            # Using parsefactories to collect fixtures in __init__.py their baseid will
-            # end with "__init__.py", thus limiting the scope of the fixture to the
-            # init module. Therefore, we tell the pluginmanager explicitly to collect
-            # the fixtures in the init module, but strip "__init__.py" from the baseid
-            # Possibly related to https://github.com/pytest-dev/pytest/issues/4085
-            collector.obj.__pytest_asyncio_scoped_event_loop = scoped_event_loop
-            fixturemanager = collector.config.pluginmanager.get_plugin("funcmanage")
-            package_node_id = _removesuffix(collector.nodeid, "__init__.py")
-            fixturemanager.parsefactories(collector.obj, nodeid=package_node_id)
-            return collector.__original_collect()
+            # When collector is a Package, collector.obj is the package's __init__.py.
+            # Accessing the __init__.py to attach the fixture function may trigger
+            # additional module imports or change the order of imports, which leads to
+            # a number of problems.
+            # see https://github.com/pytest-dev/pytest-asyncio/issues/729
+            # Moreover, Package.obj has been removed in pytest 8.
+            # Therefore, pytest-asyncio creates a temporary Python module inside the
+            # collected package. The sole purpose of that module is to house a fixture
+            # function for the pacakge-scoped event loop fixture. Once the fixture
+            # has been evaluated by pytest, the temporary module can be removed.
+            with NamedTemporaryFile(
+                dir=collector.path.parent,
+                prefix="pytest_asyncio_virtual_module_",
+                suffix=".py",
+            ) as virtual_module_file:
+                virtual_module = Module.from_parent(
+                    collector, path=Path(virtual_module_file.name)
+                )
+                virtual_module_file.write(
+                    dedent(
+                        f"""\
+                        import asyncio
+                        import pytest
+                        from pytest_asyncio.plugin import _temporary_event_loop_policy
+                        @pytest.fixture(
+                            scope="{collector_scope}",
+                            name="{collector.nodeid}::<event_loop>",
+                        )
+                        def scoped_event_loop(
+                            *args,
+                            event_loop_policy,
+                        ):
+                            new_loop_policy = event_loop_policy
+                            with _temporary_event_loop_policy(new_loop_policy):
+                                loop = asyncio.new_event_loop()
+                                loop.__pytest_asyncio = True
+                                asyncio.set_event_loop(loop)
+                                yield loop
+                                loop.close()
+                        """
+                    ).encode()
+                )
+                virtual_module_file.flush()
+                # Pytest's fixture matching algorithm compares a fixture's baseid with
+                # an Item's nodeid to determine whether a fixture is available for a
+                # specific Item. Since Package.nodeid ends with __init__.py, the
+                # fixture's baseid will also end with __init__.py, which prevents
+                # the fixture from being matched to test items in the current package.
+                # Since the fixture matching is purely based on string comparison, we
+                # strip the __init__.py suffix from the Package's node ID and
+                # tell the fixturemanager to collect the fixture with the modified
+                # nodeid. This makes the fixture visible to all items in the package.
+                # see also https://github.com/pytest-dev/pytest/issues/11662#issuecomment-1879310072  # noqa
+                # Possibly related to https://github.com/pytest-dev/pytest/issues/4085
+                fixturemanager = collector.config.pluginmanager.get_plugin("funcmanage")
+                package_node_id = _removesuffix(collector.nodeid, "__init__.py")
+                fixturemanager.parsefactories(
+                    virtual_module.obj, nodeid=package_node_id
+                )
+                yield virtual_module
+            yield from collector.__original_collect()
 
         collector.__original_collect = collector.collect
         collector.collect = _patched_collect