Correct annotation of headers parameter of HTTP event handlers #5854
Conversation
While the documentation of `BaseHandler.http_error_default()` describes the `hdrs` (`headers` in most other handlers) as "a mapping object with the headers of the error", the implementation that is located in `URLopener._open_generic_http()` will pass `response.msg` instead, which is of type `http.client.HTTPMessage`.
When the standard library constructs `HTTPError`, it will pass an `http.client.HTTPMessage`, which is a subclass of `email.message.Message`. Picking the superclass for the annotations gives users the flexibility to for example the result of the `email.message_from_X()` functions. The only thing unique to `HTTPMessage` is the undocumented `getallmatchingheaders()` method, which is only called by `http.server.CGIHTTPRequestHandler.run_cgi()`. That class gets its headers from `http.client.parse_headers()` and not from `HTTPError`, so I think it's safe to use `Message` as the annotation.
mthuurne
force-pushed
the
http-handler-headers
branch
from
3919b6a to
92bff52
Compare
This comment has been minimized.
This comment has been minimized.
2 similar comments
This comment has been minimized.
This comment has been minimized.
|
According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
|
fwiw, this makes it a little annoying to mock an |
I actually had the same issue. The documentation just states:
The stdlib always initializes |
|
Maybe custom |
|
it wasn't too difficult to update for me, though def _msg(dct: Mapping[str, str]) -> email.message.Message:
msg = email.message.Message()
for k, v in dct.items():
msg[k] = v
return msg |
The standard library implementation (I checked Python 3.8.10) passes
http.client.HTTPMessagefor the headers parameter, which does not implementMapping[str, str]: the value type isAnyinstead ofstrand__iter__()is missing. AlsoHTTPMessagehas a lot of methods that are not present inMapping.Please read the individual commit comments for more details.