1# Copyright 2021 The Duet Authors 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); 4# you may not use this file except in compliance with the License. 5# You may obtain a copy of the License at 6# 7# https://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, 11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12# See the License for the specific language governing permissions and 13# limitations under the License. 14 15"""Mypy plugin to provide better typechecking of duet functions. 16 17For more information about mypy plugins see: 18https://mypy.readthedocs.io/en/stable/extending_mypy.html#extending-mypy-using-plugins 19""" 20 21from typing import Callable, Optional 22 23from mypy.plugin import FunctionContext, Plugin 24from mypy.types import CallableType, get_proper_type, Instance, Type 25 26 27def duet_sync_callback(ctx: FunctionContext) -> Type: 28 """Callback to provide an accurate signature for duet.sync. 29 30 The duet.sync function wraps an async callable in a synchronous wrapper: 31 32 def sync(f: Callable[..., Awaitable[T]]) -> Callable[..., T]: 33 34 This plugin basically tells mypy that the two ellipses are exactly the same, 35 that is, that the new synchronous callable accepts exactly the same args as 36 the original function. This allows for precise typechecking of calls to 37 functions wrapped by duet.sync. 38 """ 39 func_type = get_proper_type(ctx.arg_types[0][0]) 40 if not isinstance(func_type, CallableType): 41 ctx.api.msg.fail(f"expected Callable[..., Awaitable[T]], got {func_type}", ctx.context) 42 return ctx.default_return_type 43 44 # Note that the return type of an async function is Coroutine[Any, Any, T], 45 # which is a subtype of Awaitable[T]. See: 46 # https://mypy.readthedocs.io/en/stable/more_types.html#typing-async-await 47 ret_type = get_proper_type(func_type.ret_type) 48 if not (isinstance(ret_type, Instance) and ret_type.type.name == "Coroutine"): 49 if not func_type.implicit: 50 ctx.api.msg.fail(f"expected return type Awaitable[T], got {ret_type}", ctx.context) 51 return ctx.default_return_type 52 53 result_type = ret_type.args[-1] 54 return func_type.copy_modified(ret_type=result_type) 55 56 57class DuetPlugin(Plugin): 58 def get_function_hook(self, fullname: str) -> Optional[Callable[[FunctionContext], Type]]: 59 if fullname == "duet.api.sync": 60 return duet_sync_callback 61 return None 62 63 64def plugin(version: str): 65 return DuetPlugin 66