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Move imports of `ThreadPoolExecutor` into `reformat_many()`, allowing Black-in-the...
[etc/vim.git] / src / blackd / middlewares.py
1 from typing import Iterable, Awaitable, Callable
2 from aiohttp.web_response import StreamResponse
3 from aiohttp.web_request import Request
4 from aiohttp.web_middlewares import middleware
5
6 Handler = Callable[[Request], Awaitable[StreamResponse]]
7 Middleware = Callable[[Request, Handler], Awaitable[StreamResponse]]
8
9
10 def cors(allow_headers: Iterable[str]) -> Middleware:
11     @middleware
12     async def impl(request: Request, handler: Handler) -> StreamResponse:
13         is_options = request.method == "OPTIONS"
14         is_preflight = is_options and "Access-Control-Request-Method" in request.headers
15         if is_preflight:
16             resp = StreamResponse()
17         else:
18             resp = await handler(request)
19
20         origin = request.headers.get("Origin")
21         if not origin:
22             return resp
23
24         resp.headers["Access-Control-Allow-Origin"] = "*"
25         resp.headers["Access-Control-Expose-Headers"] = "*"
26         if is_options:
27             resp.headers["Access-Control-Allow-Headers"] = ", ".join(allow_headers)
28             resp.headers["Access-Control-Allow-Methods"] = ", ".join(
29                 ("OPTIONS", "POST")
30             )
31
32         return resp
33
34     return impl  # type: ignore