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# -*- coding: utf-8 -*-
# Copyright 2020 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""This is a mypy plugin for Synpase to deal with some of the funky typing that
can crop up, e.g the cache descriptors.
"""
from typing import Callable, Optional
from mypy.nodes import ARG_NAMED_OPT
from mypy.plugin import MethodSigContext, Plugin
from mypy.typeops import bind_self
from mypy.types import CallableType, NoneType
class SynapsePlugin(Plugin):
def get_method_signature_hook(
self, fullname: str
) -> Optional[Callable[[MethodSigContext], CallableType]]:
if fullname.startswith(
"synapse.util.caches.descriptors._CachedFunction.__call__"
):
return cached_function_method_signature
return None
def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
"""Fixes the `_CachedFunction.__call__` signature to be correct.
It already has *almost* the correct signature, except:
1. the `self` argument needs to be marked as "bound";
2. any `cache_context` argument should be removed;
3. an optional keyword argument `on_invalidated` should be added.
"""
# First we mark this as a bound function signature.
signature = bind_self(ctx.default_signature)
# Secondly, we remove any "cache_context" args.
#
# Note: We should be only doing this if `cache_context=True` is set, but if
# it isn't then the code will raise an exception when its called anyway, so
# its not the end of the world.
context_arg_index = None
for idx, name in enumerate(signature.arg_names):
if name == "cache_context":
context_arg_index = idx
break
arg_types = list(signature.arg_types)
arg_names = list(signature.arg_names)
arg_kinds = list(signature.arg_kinds)
if context_arg_index:
arg_types.pop(context_arg_index)
arg_names.pop(context_arg_index)
arg_kinds.pop(context_arg_index)
# Third, we add an optional "on_invalidate" argument.
#
# This is a callable which accepts no input and returns nothing.
calltyp = CallableType(
arg_types=[],
arg_kinds=[],
arg_names=[],
ret_type=NoneType(),
fallback=ctx.api.named_generic_type("builtins.function", []),
)
arg_types.append(calltyp)
arg_names.append("on_invalidate")
arg_kinds.append(ARG_NAMED_OPT) # Arg is an optional kwarg.
signature = signature.copy_modified(
arg_types=arg_types, arg_names=arg_names, arg_kinds=arg_kinds,
)
return signature
def plugin(version: str):
# This is the entry point of the plugin, and let's us deal with the fact
# that the mypy plugin interface is *not* stable by looking at the version
# string.
#
# However, since we pin the version of mypy Synapse uses in CI, we don't
# really care.
return SynapsePlugin
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