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HTTPResponse is not recognized as a subtype of typing.IO #3108
Description
From SO:
request = urllib.request.Request(get_file_url, headers=self.data_api_headers)
with urllib.request.urlopen(request) as response:
with open(export_file_path, 'wb') as out_file:
shutil.copyfileobj(response, out_file)
This fails with Argument 1 to "copyfileobj" has incompatible type "Union[HTTPResponse, BinaryIO]"; expected IO[Any] because HTTPResponse derives from io.BufferedIOBase, which (despite being a binary IO) does not derive from typing.BinaryIO (nor does io.RawIOBase; also io.IOBase does not derive from typing.IO).
When I attempted to derive them as I thought would make sense, I got errors because __enter__ and other methods are defined both in io.IOBase and in typing.BinaryIO.
Not sure how to solve it.
Activity
ilevkivskyi commentedon Apr 2, 2017
I think this kind of problems could be solved by protocols. I have encountered many similar issues recently. I will probably submit a PR today or tomorrow.
(Note that extensive changes to typeshed may be required, replacing nominal types with corresponding protocols).
JelleZijlstra commentedon Apr 2, 2017
The IO types are especially complicated; there are lots of different "file-like" types with subtly different sets of methods. Maybe somebody will need to spend the time to carefully review all file-like types in the standard library to come up with a good set of protocols.
emmatyping commentedon Jun 4, 2018
This came up again in python/typeshed#2188 (comment) it seems.
JelleZijlstra commentedon Jun 4, 2018
This seems like a typeshed bug, not a mypy bug.
asottile commentedon Jun 4, 2018
I've copied this issue to typeshed: python/typeshed#2189