Library import 16 (#2433)

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1 files changed, 142 insertions, 0 deletions

diff --git a/contrib/tools/python3/Lib/unittest/async_case.py b/contrib/tools/python3/Lib/unittest/async_case.py
new file mode 100644
index 0000000000..bd2a471156
--- /dev/null
+++ b/contrib/tools/python3/Lib/unittest/async_case.py
@@ -0,0 +1,142 @@
+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()