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Editing: async_case.py
import asyncio import contextvars import inspect import warnings from .case import TestCase class IsolatedAsyncioTestCase(TestCase): # Names intentionally have a long prefix # to reduce a chance of clashing with user-defined attributes # from inherited test case # # The class doesn't call loop.run_until_complete(self.setUp()) and family # but uses a different approach: # 1. create a long-running task that reads self.setUp() # awaitable from queue along with a future # 2. await the awaitable object passing in and set the result # into the future object # 3. Outer code puts the awaitable and the future object into a queue # with waiting for the future # The trick is necessary because every run_until_complete() call # creates a new task with embedded ContextVar context. # To share contextvars between setUp(), test and tearDown() we need to execute # them inside the same task. # Note: the test case modifies event loop policy if the policy was not instantiated # yet. # asyncio.get_event_loop_policy() creates a default policy on demand but never # returns None # I believe this is not an issue in user level tests but python itself for testing # should reset a policy in every test module # by calling asyncio.set_event_loop_policy(None) in tearDownModule() def __init__(self, methodName='runTest'): super().__init__(methodName) self._asyncioRunner = None self._asyncioTestContext = contextvars.copy_context() async def asyncSetUp(self): pass async def asyncTearDown(self): pass def addAsyncCleanup(self, func, /, *args, **kwargs): # A trivial trampoline to addCleanup() # the function exists because it has a different semantics # and signature: # addCleanup() accepts regular functions # but addAsyncCleanup() accepts coroutines # # We intentionally don't add inspect.iscoroutinefunction() check # for func argument because there is no way # to check for async function reliably: # 1. It can be "async def func()" itself # 2. Class can implement "async def __call__()" method # 3. Regular "def func()" that returns awaitable object self.addCleanup(*(func, *args), **kwargs) async def enterAsyncContext(self, cm): """Enters the supplied asynchronous context manager. If successful, also adds its __aexit__ method as a cleanup function and returns the result of the __aenter__ method. """ # We look up the special methods on the type to match the with # statement. cls = type(cm) try: enter = cls.__aenter__ exit = cls.__aexit__ except AttributeError: raise TypeError(f"'{cls.__module__}.{cls.__qualname__}' object does " f"not support the asynchronous context manager protocol" ) from None result = await enter(cm) self.addAsyncCleanup(exit, cm, None, None, None) return result def _callSetUp(self): # Force loop to be initialized and set as the current loop # so that setUp functions can use get_event_loop() and get the # correct loop instance. self._asyncioRunner.get_loop() self._asyncioTestContext.run(self.setUp) self._callAsync(self.asyncSetUp) def _callTestMethod(self, method): if self._callMaybeAsync(method) is not None: warnings.warn(f'It is deprecated to return a value that is not None from a ' f'test case ({method})', DeprecationWarning, stacklevel=4) def _callTearDown(self): self._callAsync(self.asyncTearDown) self._asyncioTestContext.run(self.tearDown) def _callCleanup(self, function, *args, **kwargs): self._callMaybeAsync(function, *args, **kwargs) def _callAsync(self, func, /, *args, **kwargs): assert self._asyncioRunner is not None, 'asyncio runner is not initialized' assert inspect.iscoroutinefunction(func), f'{func!r} is not an async function' return self._asyncioRunner.run( func(*args, **kwargs), context=self._asyncioTestContext ) def _callMaybeAsync(self, func, /, *args, **kwargs): assert self._asyncioRunner is not None, 'asyncio runner is not initialized' if inspect.iscoroutinefunction(func): return self._asyncioRunner.run( func(*args, **kwargs), context=self._asyncioTestContext, ) else: return self._asyncioTestContext.run(func, *args, **kwargs) def _setupAsyncioRunner(self): assert self._asyncioRunner is None, 'asyncio runner is already initialized' runner = asyncio.Runner(debug=True) self._asyncioRunner = runner def _tearDownAsyncioRunner(self): runner = self._asyncioRunner runner.close() def run(self, result=None): self._setupAsyncioRunner() try: return super().run(result) finally: self._tearDownAsyncioRunner() def debug(self): self._setupAsyncioRunner() super().debug() self._tearDownAsyncioRunner() def __del__(self): if self._asyncioRunner is not None: self._tearDownAsyncioRunner()
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