requests: Allow files={"example": ("filename", bytes)}

[prauscher]

According to https://github.com/psf/requests/blob/2d5517682b3b38547634d153cea43d48fbc8cdb5/requests/models.py#L170 It should be possible to provide files={"fieldname": ("filename", [bytes-object])}, but since the last update of mypy this fails with

packet_analyser/daemon/uploader.py:78: error: Argument "files" to "post" has incompatible type "Dict[str, Tuple[str, bytes]]"; expected "Optional[Union[MutableMapping[str, IO[Any]], MutableMapping[str, Tuple[Optional[str], IO[Any]]], MutableMapping[str, Tuple[Optional[str], IO[Any], str]], MutableMapping[str, Tuple[Optional[str], IO[Any], str, MutableMapping[str, str]]]]]"  [arg-type]

The issue seems to be in

typeshed/stubs/requests/requests/sessions.pyi

Lines 51 to 56 in 63fb9af

	_Files: TypeAlias = (
	MutableMapping[str, IO[Any]]
	| MutableMapping[str, tuple[str | None, IO[Any]]]
	| MutableMapping[str, tuple[str | None, IO[Any], str]]
	| MutableMapping[str, tuple[str | None, IO[Any], str, _TextMapping]]
	)

Can this be fixed?

[bersbersbers]

I see a similar issue for the example from https://docs.python-requests.org/en/latest/user/quickstart/#post-a-multipart-encoded-file:

import requests

url = "https://httpbin.org/post"
files = {"file": open("report.xls", "rb")}

r = requests.post(url, files=files)

bug.py:6: error: Argument "files" to "post" has incompatible type "Dict[str, BufferedReader]"; expected "Optional[Union[MutableMapping[str, IO[Any]], MutableMapping[str, Tuple[str, IO[Any]]], MutableMapping[str, Tuple[str, IO[Any], str]], MutableMapping[str, Tuple[str, IO[Any], str, MutableMapping[str, str]]]]]" [arg-type]

This issue reproduces with mypy==0.942 and types-requests==2.27.21, but not with types-requests==2.27.20.

[bersbersbers]

I'd say the issue is in #7696, specifically, https://github.com/python/typeshed/pull/7696/files#diff-c7fb924dc4d234c3cc1a615ee40522b3a0bb8641f0662ecb1a89762a090b8db9R32 and https://github.com/python/typeshed/pull/7696/files#diff-bfcfcf0d08b5e5c2965394517079c5cfb2b2a11b2e27cf9d08fb07090cd9a4ceR51.

[shawnwall]

I'm also seeing this issue when utilizing StringIO in a test:

response = client.put(
    f"{BASE_PATH}/name/file-import",
    files={"file": StringIO("mockfile")},
)

error: Argument "files" to "post" has incompatible type "Dict[str, Tuple[str, bytes]]"; expected "Optional[Union[MutableMapping[str, IO[Any]], MutableMapping[str, Tuple[Optional[str], IO[Any]]], MutableMapping[str, Tuple[Optional[str], IO[Any], str]], MutableMapping[str, Tuple[Optional[str], IO[Any], str, MutableMapping[str, str]]]]]"  [arg-type]

[AlexWaygood]

Thanks all — a new version of types-requests should be uploaded to PyPI shortly. Feel free to leave a comment here or open a new issue if there are still problems with the new release :)

[bersbersbers]

I have tried 2.27.23 and while the error message has changed, it is still there:

bug.py:6: error: Argument "files" to "post" has incompatible type "Dict[str, BufferedReader]"; expected "Optional[Union[MutableMapping[str, Union[SupportsRead[Union[str, bytes]], str, bytes]], MutableMapping[str, Tuple[Optional[str], Union[SupportsRead[Union[str, bytes]], str, bytes]]], MutableMapping[str, Tuple[Optional[str], Union[SupportsRead[Union[str, bytes]], str, bytes], str]], MutableMapping[str, Tuple[Optional[str], Union[SupportsRead[Union[str, bytes]], str, bytes], str, MutableMapping[str, str]]]]]" [arg-type]

This is with the code example from #7724 (comment)

[etiennecrb]

I think this issue should be reopened. The problem here I believe is the usage of MutableMapping which is invariant. Mypy recommends using immutable collections as annotations when possible so I believe Mapping should be used here (if it's true that it is not mutated), otherwise we might be stuck.

Edit: sorry, didn't see the new issue opened, which properly describes the problem.

[AlexWaygood]

Okay, #7732 has just been merged, and a new release will be uploaded shortly — please let us know if there are still problems with the new release!

[bersbersbers]

2.27.24 works fine for me, thanks for the quick fix!

[svenpanne]

I am not really sure if this bug should be closed: Using MutableMapping instead of Mapping seems to be wrong at several other places, too: _TextMapping, which is mutable, is e.g. used for headers or cookies kwargs, but I somehow doubt that those arguments are actually mutated.

This incorrect(?) variance leads to quite a few false positives on our SW, and I guess we're not alone with this...