153 lines
6.1 KiB
Python
153 lines
6.1 KiB
Python
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"""
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Call loop machinery
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"""
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from __future__ import annotations
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from typing import cast
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from typing import Generator
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from typing import Mapping
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from typing import Sequence
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from typing import Tuple
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from typing import Union
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from ._hooks import HookImpl
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from ._result import _raise_wrapfail
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from ._result import HookCallError
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from ._result import Result
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# Need to distinguish between old- and new-style hook wrappers.
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# Wrapping one a singleton tuple is the fastest type-safe way I found to do it.
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Teardown = Union[
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Tuple[Generator[None, Result[object], None]],
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Generator[None, object, object],
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]
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def _multicall(
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hook_name: str,
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hook_impls: Sequence[HookImpl],
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caller_kwargs: Mapping[str, object],
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firstresult: bool,
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) -> object | list[object]:
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"""Execute a call into multiple python functions/methods and return the
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result(s).
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``caller_kwargs`` comes from HookCaller.__call__().
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"""
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__tracebackhide__ = True
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results: list[object] = []
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exception = None
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only_new_style_wrappers = True
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try: # run impl and wrapper setup functions in a loop
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teardowns: list[Teardown] = []
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try:
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for hook_impl in reversed(hook_impls):
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try:
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args = [caller_kwargs[argname] for argname in hook_impl.argnames]
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except KeyError:
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for argname in hook_impl.argnames:
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if argname not in caller_kwargs:
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raise HookCallError(
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f"hook call must provide argument {argname!r}"
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)
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if hook_impl.hookwrapper:
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only_new_style_wrappers = False
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try:
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# If this cast is not valid, a type error is raised below,
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# which is the desired response.
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res = hook_impl.function(*args)
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wrapper_gen = cast(Generator[None, Result[object], None], res)
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next(wrapper_gen) # first yield
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teardowns.append((wrapper_gen,))
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except StopIteration:
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_raise_wrapfail(wrapper_gen, "did not yield")
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elif hook_impl.wrapper:
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try:
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# If this cast is not valid, a type error is raised below,
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# which is the desired response.
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res = hook_impl.function(*args)
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function_gen = cast(Generator[None, object, object], res)
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next(function_gen) # first yield
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teardowns.append(function_gen)
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except StopIteration:
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_raise_wrapfail(function_gen, "did not yield")
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else:
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res = hook_impl.function(*args)
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if res is not None:
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results.append(res)
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if firstresult: # halt further impl calls
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break
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except BaseException as exc:
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exception = exc
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finally:
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# Fast path - only new-style wrappers, no Result.
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if only_new_style_wrappers:
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if firstresult: # first result hooks return a single value
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result = results[0] if results else None
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else:
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result = results
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# run all wrapper post-yield blocks
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for teardown in reversed(teardowns):
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try:
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if exception is not None:
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teardown.throw(exception) # type: ignore[union-attr]
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else:
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teardown.send(result) # type: ignore[union-attr]
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# Following is unreachable for a well behaved hook wrapper.
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# Try to force finalizers otherwise postponed till GC action.
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# Note: close() may raise if generator handles GeneratorExit.
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teardown.close() # type: ignore[union-attr]
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except StopIteration as si:
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result = si.value
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exception = None
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continue
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except BaseException as e:
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exception = e
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continue
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_raise_wrapfail(teardown, "has second yield") # type: ignore[arg-type]
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if exception is not None:
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raise exception.with_traceback(exception.__traceback__)
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else:
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return result
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# Slow path - need to support old-style wrappers.
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else:
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if firstresult: # first result hooks return a single value
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outcome: Result[object | list[object]] = Result(
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results[0] if results else None, exception
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)
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else:
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outcome = Result(results, exception)
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# run all wrapper post-yield blocks
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for teardown in reversed(teardowns):
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if isinstance(teardown, tuple):
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try:
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teardown[0].send(outcome)
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_raise_wrapfail(teardown[0], "has second yield")
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except StopIteration:
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pass
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else:
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try:
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if outcome._exception is not None:
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teardown.throw(outcome._exception)
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else:
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teardown.send(outcome._result)
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# Following is unreachable for a well behaved hook wrapper.
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# Try to force finalizers otherwise postponed till GC action.
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# Note: close() may raise if generator handles GeneratorExit.
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teardown.close()
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except StopIteration as si:
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outcome.force_result(si.value)
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continue
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except BaseException as e:
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outcome.force_exception(e)
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continue
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_raise_wrapfail(teardown, "has second yield")
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return outcome.get_result()
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