mirror of
https://github.com/element-hq/synapse.git
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144 lines
5.2 KiB
Python
144 lines
5.2 KiB
Python
# Copyright 2020 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""This is a mypy plugin for Synpase to deal with some of the funky typing that
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can crop up, e.g the cache descriptors.
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"""
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from typing import Callable, Optional, Type
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from mypy.erasetype import remove_instance_last_known_values
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from mypy.nodes import ARG_NAMED_OPT
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from mypy.plugin import MethodSigContext, Plugin
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from mypy.typeops import bind_self
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from mypy.types import CallableType, Instance, NoneType, UnionType
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class SynapsePlugin(Plugin):
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def get_method_signature_hook(
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self, fullname: str
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) -> Optional[Callable[[MethodSigContext], CallableType]]:
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if fullname.startswith(
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(
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"synapse.util.caches.descriptors.CachedFunction.__call__",
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"synapse.util.caches.descriptors._LruCachedFunction.__call__",
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)
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):
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return cached_function_method_signature
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return None
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def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
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"""Fixes the `CachedFunction.__call__` signature to be correct.
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It already has *almost* the correct signature, except:
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1. the `self` argument needs to be marked as "bound";
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2. any `cache_context` argument should be removed;
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3. an optional keyword argument `on_invalidated` should be added.
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"""
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# First we mark this as a bound function signature.
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signature = bind_self(ctx.default_signature)
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# Secondly, we remove any "cache_context" args.
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#
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# Note: We should be only doing this if `cache_context=True` is set, but if
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# it isn't then the code will raise an exception when its called anyway, so
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# its not the end of the world.
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context_arg_index = None
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for idx, name in enumerate(signature.arg_names):
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if name == "cache_context":
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context_arg_index = idx
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break
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arg_types = list(signature.arg_types)
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arg_names = list(signature.arg_names)
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arg_kinds = list(signature.arg_kinds)
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if context_arg_index:
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arg_types.pop(context_arg_index)
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arg_names.pop(context_arg_index)
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arg_kinds.pop(context_arg_index)
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# Third, we add an optional "on_invalidate" argument.
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#
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# This is a either
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# - a callable which accepts no input and returns nothing, or
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# - None.
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calltyp = UnionType(
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[
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NoneType(),
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CallableType(
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arg_types=[],
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arg_kinds=[],
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arg_names=[],
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ret_type=NoneType(),
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fallback=ctx.api.named_generic_type("builtins.function", []),
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),
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]
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)
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arg_types.append(calltyp)
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arg_names.append("on_invalidate")
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arg_kinds.append(ARG_NAMED_OPT) # Arg is an optional kwarg.
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# Finally we ensure the return type is a Deferred.
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if (
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isinstance(signature.ret_type, Instance)
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and signature.ret_type.type.fullname == "twisted.internet.defer.Deferred"
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):
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# If it is already a Deferred, nothing to do.
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ret_type = signature.ret_type
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else:
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ret_arg = None
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if isinstance(signature.ret_type, Instance):
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# If a coroutine, wrap the coroutine's return type in a Deferred.
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if signature.ret_type.type.fullname == "typing.Coroutine":
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ret_arg = signature.ret_type.args[2]
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# If an awaitable, wrap the awaitable's final value in a Deferred.
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elif signature.ret_type.type.fullname == "typing.Awaitable":
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ret_arg = signature.ret_type.args[0]
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# Otherwise, wrap the return value in a Deferred.
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if ret_arg is None:
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ret_arg = signature.ret_type
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# This should be able to use ctx.api.named_generic_type, but that doesn't seem
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# to find the correct symbol for anything more than 1 module deep.
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#
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# modules is not part of CheckerPluginInterface. The following is a combination
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# of TypeChecker.named_generic_type and TypeChecker.lookup_typeinfo.
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sym = ctx.api.modules["twisted.internet.defer"].names.get("Deferred") # type: ignore[attr-defined]
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ret_type = Instance(sym.node, [remove_instance_last_known_values(ret_arg)])
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signature = signature.copy_modified(
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arg_types=arg_types,
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arg_names=arg_names,
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arg_kinds=arg_kinds,
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ret_type=ret_type,
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)
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return signature
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def plugin(version: str) -> Type[SynapsePlugin]:
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# This is the entry point of the plugin, and lets us deal with the fact
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# that the mypy plugin interface is *not* stable by looking at the version
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# string.
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#
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# However, since we pin the version of mypy Synapse uses in CI, we don't
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# really care.
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return SynapsePlugin
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