Accept async fixtures in pytest plugin (aio-libs#2223)

aiohttp/helpers.py

@@ -6,6 +6,7 @@
 import cgi
 import datetime
 import functools
+import inspect
 import os
 import re
 import sys
@@ -821,3 +822,9 @@ def update_cookies(self, cookies, response_url=None):
 
     def filter_cookies(self, request_url):
         return None
+
+
+def isasyncgenfunction(obj):
+    if hasattr(inspect, 'isasyncgenfunction'):
+        return inspect.isasyncgenfunction(obj)
+    return False

aiohttp/pytest_plugin.py

@@ -7,6 +7,7 @@
 import pytest
 from py import path
 
+from aiohttp.helpers import isasyncgenfunction
 from aiohttp.web import Application
 
 from .test_utils import unused_port as _unused_port
@@ -37,6 +38,53 @@ def pytest_addoption(parser):
         help='enable event loop debug mode')
 
 
+def pytest_fixture_setup(fixturedef, request):
+    """
+    Allow fixtures to be coroutines. Run coroutine fixtures in an event loop.
+    """
+    func = fixturedef.func
+
+    if isasyncgenfunction(func):
+        # async generator fixture
+        is_async_gen = True
+    elif asyncio.iscoroutinefunction(func):
+        # regular async fixture
+        is_async_gen = False
+    else:
+        # not an async fixture, nothing to do
+        return
+
+    # if neither the fixture nor the test use the 'loop' fixture,
+    # 'getfixturevalue' will fail because the test is not parameterized
+    # (this can be removed someday if 'loop' is no longer parameterized)
+    if 'loop' not in request.fixturenames:
+        raise Exception(
+            "Asynchronous fixtures must depend on the 'loop' fixture or be "
+            "used in tests depending from it."
+        )
+
+    def wrapper(*args, **kwargs):
+        _loop = request.getfixturevalue('loop')
+
+        if is_async_gen:
+            # for async generators, we need to advance the generator once,
+            # then advance it again in a finalizer
+            gen = func(*args, **kwargs)
+
+            def finalizer():
+                try:
+                    return _loop.run_until_complete(gen.__anext__())
+                except StopAsyncIteration:
+                    pass
+
+            request.addfinalizer(finalizer)
+            return _loop.run_until_complete(gen.__anext__())
+        else:
+            return _loop.run_until_complete(func(*args, **kwargs))
+
+    fixturedef.func = wrapper
+
+
 @pytest.fixture
 def fast(request):
     """ --fast config option """