Support parametrized event_loop fixture (#278)

README.rst

@@ -261,6 +261,7 @@ Changelog
 ~~~~~~~~~~~~~~~~~~~
 
 - Raise a warning if @pytest.mark.asyncio is applied to non-async function. `#275 <https://github.com/pytest-dev/pytest-asyncio/issues/275>`_
+- Support parametrized ``event_loop`` fixture. `#278 <https://github.com/pytest-dev/pytest-asyncio/issues/278>`_
 
 0.17.2 (22-01-17)
 ~~~~~~~~~~~~~~~~~~~

pytest_asyncio/plugin.py

@@ -165,7 +165,7 @@ def _set_explicit_asyncio_mark(obj: Any) -> None:
 
 def _is_coroutine(obj: Any) -> bool:
     """Check to see if an object is really an asyncio coroutine."""
-    return asyncio.iscoroutinefunction(obj) or inspect.isgeneratorfunction(obj)
+    return asyncio.iscoroutinefunction(obj)
 
 
 def _is_coroutine_or_asyncgen(obj: Any) -> bool:
@@ -198,6 +198,118 @@ def pytest_report_header(config: Config) -> List[str]:
     return [f"asyncio: mode={mode}"]
 
 
+def _preprocess_async_fixtures(config: Config, holder: Set[FixtureDef]) -> None:
+    asyncio_mode = _get_asyncio_mode(config)
+    fixturemanager = config.pluginmanager.get_plugin("funcmanage")
+    for fixtures in fixturemanager._arg2fixturedefs.values():
+        for fixturedef in fixtures:
+            if fixturedef is holder:
+                continue
+            func = fixturedef.func
+            if not _is_coroutine_or_asyncgen(func):
+                # Nothing to do with a regular fixture function
+                continue
+            if not _has_explicit_asyncio_mark(func):
+                if asyncio_mode == Mode.AUTO:
+                    # Enforce asyncio mode if 'auto'
+                    _set_explicit_asyncio_mark(func)
+                elif asyncio_mode == Mode.LEGACY:
+                    _set_explicit_asyncio_mark(func)
+                    try:
+                        code = func.__code__
+                    except AttributeError:
+                        code = func.__func__.__code__
+                    name = (
+                        f"<fixture {func.__qualname__}, file={code.co_filename}, "
+                        f"line={code.co_firstlineno}>"
+                    )
+                    warnings.warn(
+                        LEGACY_ASYNCIO_FIXTURE.format(name=name),
+                        DeprecationWarning,
+                    )
+
+            to_add = []
+            for name in ("request", "event_loop"):
+                if name not in fixturedef.argnames:
+                    to_add.append(name)
+
+            if to_add:
+                fixturedef.argnames += tuple(to_add)
+
+            if inspect.isasyncgenfunction(func):
+                fixturedef.func = _wrap_asyncgen(func)
+            elif inspect.iscoroutinefunction(func):
+                fixturedef.func = _wrap_async(func)
+
+            assert _has_explicit_asyncio_mark(fixturedef.func)
+            holder.add(fixturedef)
+
+
+def _add_kwargs(
+    func: Callable[..., Any],
+    kwargs: Dict[str, Any],
+    event_loop: asyncio.AbstractEventLoop,
+    request: SubRequest,
+) -> Dict[str, Any]:
+    sig = inspect.signature(func)
+    ret = kwargs.copy()
+    if "request" in sig.parameters:
+        ret["request"] = request
+    if "event_loop" in sig.parameters:
+        ret["event_loop"] = event_loop
+    return ret
+
+
+def _wrap_asyncgen(func: Callable[..., AsyncIterator[_R]]) -> Callable[..., _R]:
+    @functools.wraps(func)
+    def _asyncgen_fixture_wrapper(
+        event_loop: asyncio.AbstractEventLoop, request: SubRequest, **kwargs: Any
+    ) -> _R:
+        gen_obj = func(**_add_kwargs(func, kwargs, event_loop, request))
+
+        async def setup() -> _R:
+            res = await gen_obj.__anext__()
+            return res
+
+        def finalizer() -> None:
+            """Yield again, to finalize."""
+
+            async def async_finalizer() -> None:
+                try:
+                    await gen_obj.__anext__()
+                except StopAsyncIteration:
+                    pass
+                else:
+                    msg = "Async generator fixture didn't stop."
+                    msg += "Yield only once."
+                    raise ValueError(msg)
+
+            event_loop.run_until_complete(async_finalizer())
+
+        result = event_loop.run_until_complete(setup())
+        request.addfinalizer(finalizer)
+        return result
+
+    return _asyncgen_fixture_wrapper
+
+
+def _wrap_async(func: Callable[..., Awaitable[_R]]) -> Callable[..., _R]:
+    @functools.wraps(func)
+    def _async_fixture_wrapper(
+        event_loop: asyncio.AbstractEventLoop, request: SubRequest, **kwargs: Any
+    ) -> _R:
+        async def setup() -> _R:
+            res = await func(**_add_kwargs(func, kwargs, event_loop, request))
+            return res
+
+        return event_loop.run_until_complete(setup())
+
+    return _async_fixture_wrapper
+
+
+_HOLDER: Set[FixtureDef] = set()
+
+
 @pytest.mark.tryfirst
 def pytest_pycollect_makeitem(
     collector: Union[pytest.Module, pytest.Class], name: str, obj: object
@@ -212,6 +324,7 @@ def pytest_pycollect_makeitem(
         or _is_hypothesis_test(obj)
         and _hypothesis_test_wraps_coroutine(obj)
     ):
+        _preprocess_async_fixtures(collector.config, _HOLDER)
         item = pytest.Function.from_parent(collector, name=name)
         marker = item.get_closest_marker("asyncio")
         if marker is not None:
@@ -230,31 +343,6 @@ def _hypothesis_test_wraps_coroutine(function: Any) -> bool:
     return _is_coroutine(function.hypothesis.inner_test)
 
 
-class FixtureStripper:
-    """Include additional Fixture, and then strip them"""
-
-    EVENT_LOOP = "event_loop"
-
-    def __init__(self, fixturedef: FixtureDef) -> None:
-        self.fixturedef = fixturedef
-        self.to_strip: Set[str] = set()
-
-    def add(self, name: str) -> None:
-        """Add fixture name to fixturedef
-        and record in to_strip list (If not previously included)"""
-        if name in self.fixturedef.argnames:
-            return
-        self.fixturedef.argnames += (name,)
-        self.to_strip.add(name)
-
-    def get_and_strip_from(self, name: str, data_dict: Dict[str, _T]) -> _T:
-        """Strip name from data, and return value"""
-        result = data_dict[name]
-        if name in self.to_strip:
-            del data_dict[name]
-        return result
-
-
 @pytest.hookimpl(trylast=True)
 def pytest_fixture_post_finalizer(fixturedef: FixtureDef, request: SubRequest) -> None:
     """Called after fixture teardown"""
@@ -291,95 +379,6 @@ def pytest_fixture_setup(
         policy.set_event_loop(loop)
         return
 
-    func = fixturedef.func
-    if not _is_coroutine_or_asyncgen(func):
-        # Nothing to do with a regular fixture function
-        yield
-        return
-
-    config = request.node.config
-    asyncio_mode = _get_asyncio_mode(config)
-
-    if not _has_explicit_asyncio_mark(func):
-        if asyncio_mode == Mode.AUTO:
-            # Enforce asyncio mode if 'auto'
-            _set_explicit_asyncio_mark(func)
-        elif asyncio_mode == Mode.LEGACY:
-            _set_explicit_asyncio_mark(func)
-            try:
-                code = func.__code__
-            except AttributeError:
-                code = func.__func__.__code__
-            name = (
-                f"<fixture {func.__qualname__}, file={code.co_filename}, "
-                f"line={code.co_firstlineno}>"
-            )
-            warnings.warn(
-                LEGACY_ASYNCIO_FIXTURE.format(name=name),
-                DeprecationWarning,
-            )
-        else:
-            # asyncio_mode is STRICT,
-            # don't handle fixtures that are not explicitly marked
-            yield
-            return
-
-    if inspect.isasyncgenfunction(func):
-        # This is an async generator function. Wrap it accordingly.
-        generator = func
-
-        fixture_stripper = FixtureStripper(fixturedef)
-        fixture_stripper.add(FixtureStripper.EVENT_LOOP)
-
-        def wrapper(*args, **kwargs):
-            loop = fixture_stripper.get_and_strip_from(
-                FixtureStripper.EVENT_LOOP, kwargs
-            )
-
-            gen_obj = generator(*args, **kwargs)
-
-            async def setup():
-                res = await gen_obj.__anext__()
-                return res
-
-            def finalizer():
-                """Yield again, to finalize."""
-
-                async def async_finalizer():
-                    try:
-                        await gen_obj.__anext__()
-                    except StopAsyncIteration:
-                        pass
-                    else:
-                        msg = "Async generator fixture didn't stop."
-                        msg += "Yield only once."
-                        raise ValueError(msg)
-
-                loop.run_until_complete(async_finalizer())
-
-            result = loop.run_until_complete(setup())
-            request.addfinalizer(finalizer)
-            return result
-
-        fixturedef.func = wrapper
-    elif inspect.iscoroutinefunction(func):
-        coro = func
-
-        fixture_stripper = FixtureStripper(fixturedef)
-        fixture_stripper.add(FixtureStripper.EVENT_LOOP)
-
-        def wrapper(*args, **kwargs):
-            loop = fixture_stripper.get_and_strip_from(
-                FixtureStripper.EVENT_LOOP, kwargs
-            )
-
-            async def setup():
-                res = await coro(*args, **kwargs)
-                return res
-
-            return loop.run_until_complete(setup())
-
-        fixturedef.func = wrapper
     yield
 
 

tests/async_fixtures/test_parametrized_loop.py

@@ -0,0 +1,31 @@
+import asyncio
+
+import pytest
+
+TESTS_COUNT = 0
+
+
+def teardown_module():
+    # parametrized 2 * 2 times: 2 for 'event_loop' and 2 for 'fix'
+    assert TESTS_COUNT == 4
+
+
+@pytest.fixture(scope="module", params=[1, 2])
+def event_loop(request):
+    request.param
+    loop = asyncio.new_event_loop()
+    yield loop
+    loop.close()
+
+
+@pytest.fixture(params=["a", "b"])
+async def fix(request):
+    await asyncio.sleep(0)
+    return request.param
+
+
+@pytest.mark.asyncio
+async def test_parametrized_loop(fix):
+    await asyncio.sleep(0)
+    global TESTS_COUNT
+    TESTS_COUNT += 1