kopia lustrzana https://github.com/micropython/micropython-lib
223 wiersze
7.0 KiB
Python
223 wiersze
7.0 KiB
Python
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"""Utilities for async with-statement contexts.
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Based on original source code: https://github.com/python/cpython/blob/3.11/Lib/contextlib.py
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"""
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class ContextDecorator(object):
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"A base class or mixin that enables context managers to work as decorators."
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def _recreate_cm(self):
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"""Return a recreated instance of self.
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Allows an otherwise one-shot context manager like
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_GeneratorContextManager to support use as
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a decorator via implicit recreation.
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This is a private interface just for _GeneratorContextManager.
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See issue #11647 for details.
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"""
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return self
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def __call__(self, func):
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def inner(*args, **kwds):
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with self._recreate_cm():
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return func(*args, **kwds)
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return inner
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class _GeneratorContextManager(ContextDecorator):
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"""Helper for @contextmanager decorator."""
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def __init__(self, func, *args, **kwds):
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self.gen = func(*args, **kwds)
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self.func, self.args, self.kwds = func, args, kwds
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def _recreate_cm(self):
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# _GCM instances are one-shot context managers, so the
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# CM must be recreated each time a decorated function is
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# called
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return self.__class__(self.func, *self.args, **self.kwds)
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def __enter__(self):
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try:
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return next(self.gen)
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except StopIteration:
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raise RuntimeError("generator didn't yield") from None
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def __exit__(self, type, value, traceback):
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if type is None:
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try:
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next(self.gen)
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except StopIteration:
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return
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else:
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raise RuntimeError("generator didn't stop")
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else:
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if value is None:
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# Need to force instantiation so we can reliably
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# tell if we get the same exception back
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value = type()
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try:
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self.gen.throw(type, value, traceback)
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raise RuntimeError("generator didn't stop after throw()")
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except StopIteration as exc:
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# Suppress the exception *unless* it's the same exception that
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# was passed to throw(). This prevents a StopIteration
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# raised inside the "with" statement from being suppressed
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return exc is not value
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def contextmanager(func):
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"""@contextmanager decorator.
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Typical usage:
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@contextmanager
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def some_generator(<arguments>):
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<setup>
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try:
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yield <value>
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finally:
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<cleanup>
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This makes this:
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with some_generator(<arguments>) as <variable>:
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<body>
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equivalent to this:
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<setup>
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try:
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<variable> = <value>
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<body>
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finally:
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<cleanup>
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"""
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def helper(*args, **kwds):
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return _GeneratorContextManager(func, *args, **kwds)
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return helper
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class AsyncContextDecorator(object):
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"A base class or mixin that enables async context managers to work as decorators."
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def _recreate_cm(self):
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"""Return a recreated instance of self."""
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return self
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def __call__(self, func):
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async def inner(*args, **kwds):
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async with self._recreate_cm():
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return await func(*args, **kwds)
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return inner
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class _AsyncGeneratorContextManager(AsyncContextDecorator):
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"""Helper for @asynccontextmanager decorator."""
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def __init__(self, func, args, kwds):
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self.gen = func(*args, **kwds)
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self.func, self.args, self.kwds = func, args, kwds
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async def __aenter__(self):
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# do not keep args and kwds alive unnecessarily
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# they are only needed for recreation, which is not possible anymore
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del self.args, self.kwds, self.func
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try:
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return await anext(self.gen)
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except StopAsyncIteration:
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raise RuntimeError("generator didn't yield") from None
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async def __aexit__(self, typ, value, traceback):
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if typ is None:
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try:
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await anext(self.gen)
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except StopAsyncIteration:
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return False
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else:
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raise RuntimeError("generator didn't stop")
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else:
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if value is None:
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# Need to force instantiation so we can reliably
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# tell if we get the same exception back
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value = typ()
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try:
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await self.gen.athrow(typ, value, traceback)
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except StopAsyncIteration as exc:
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# Suppress StopIteration *unless* it's the same exception that
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# was passed to throw(). This prevents a StopIteration
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# raised inside the "with" statement from being suppressed.
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return exc is not value
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except RuntimeError as exc:
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# Don't re-raise the passed in exception. (issue27122)
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if exc is value:
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exc.__traceback__ = traceback
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return False
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# Avoid suppressing if a Stop(Async)Iteration exception
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# was passed to athrow() and later wrapped into a RuntimeError
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# (see PEP 479 for sync generators; async generators also
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# have this behavior). But do this only if the exception wrapped
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# by the RuntimeError is actually Stop(Async)Iteration (see
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# issue29692).
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if (
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isinstance(value, (StopIteration, StopAsyncIteration))
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and exc.__cause__ is value
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):
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value.__traceback__ = traceback
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return False
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raise
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except BaseException as exc:
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# only re-raise if it's *not* the exception that was
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# passed to throw(), because __exit__() must not raise
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# an exception unless __exit__() itself failed. But throw()
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# has to raise the exception to signal propagation, so this
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# fixes the impedance mismatch between the throw() protocol
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# and the __exit__() protocol.
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if exc is not value:
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raise
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exc.__traceback__ = traceback
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return False
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raise RuntimeError("generator didn't stop after athrow()")
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def asynccontextmanager(func):
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"""@asynccontextmanager decorator.
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Typical usage:
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@asynccontextmanager
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async def some_async_generator(<arguments>):
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<setup>
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try:
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yield <value>
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finally:
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<cleanup>
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This makes this:
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async with some_async_generator(<arguments>) as <variable>:
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<body>
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equivalent to this:
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<setup>
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try:
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<variable> = <value>
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<body>
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finally:
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<cleanup>
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"""
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def helper(*args, **kwds):
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return _AsyncGeneratorContextManager(func, args, kwds)
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return helper
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