Response doesn't deal well with CIMultiDictProxy headers

[ArthurKantor]

Long story short

Example badness:

from aiohttp.web_exceptions import HTTPNotFound
from multidict import CIMultiDictProxy, CIMultiDict
raise HTTPNotFound(text='hi',headers=CIMultiDictProxy(CIMultiDict()))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-12-51ed331c9efe> in <module>()
      1 from aiohttp.web_exceptions import HTTPNotFound
      2 from multidict import CIMultiDictProxy, CIMultiDict
----> 3 raise HTTPNotFound(text='hi',headers=CIMultiDictProxy(CIMultiDict()))

/usr/local/lib/python3.7/dist-packages/aiohttp/web_exceptions.py in __init__(self, headers, reason, body, text, content_type)
     79         Response.__init__(self, status=self.status_code,
     80                           headers=headers, reason=reason,
---> 81                           body=body, text=text, content_type=content_type)
     82         Exception.__init__(self, self.reason)
     83         if self.body is None and not self.empty_body:

/usr/local/lib/python3.7/dist-packages/aiohttp/web_response.py in __init__(self, body, status, reason, text, headers, content_type, charset)
    467                     charset = 'utf-8'
    468                 headers[hdrs.CONTENT_TYPE] = (
--> 469                     content_type + '; charset=' + charset)
    470                 body = text.encode(charset)
    471                 text = None

TypeError: 'CIMultiDictProxy' object does not support item assignment

This is useful e.g. when an aiohttp app is acting like a proxy and is relaying errors from backends.

Expected behaviour

same as when using CIMultiDict:

from aiohttp.web_exceptions import HTTPNotFound
from multidict import CIMultiDictProxy, CIMultiDict
raise HTTPNotFound(text='hi',headers=CIMultiDict(CIMultiDict()))

---------------------------------------------------------------------------
HTTPNotFound                              Traceback (most recent call last)
<ipython-input-14-cc0e33a6117b> in <module>()
      1 from aiohttp.web_exceptions import HTTPNotFound
      2 from multidict import CIMultiDictProxy, CIMultiDict
----> 3 raise HTTPNotFound(text='hi',headers=CIMultiDict(CIMultiDict()))

HTTPNotFound: Not Found

Actual behaviour

see above

Steps to reproduce

Your environment

AIOHTTP 3.3.2
python3.7

[webknjaz]

This might need to go to multidict project itself.

[ArthurKantor]

it seems to me that CIMultiDictProxy is actually behaving correctly. It's supposed to be immutable.

[webknjaz]

Well... Yeah. That's why it's called "proxy" :)

[ArthurKantor]

I think a simple fix would be here:
by changing

        elif not isinstance(headers, (CIMultiDict, CIMultiDictProxy)):
            headers = CIMultiDict(headers)

to

        elif not isinstance(headers, CIMultiDict):
            headers = CIMultiDict(headers)

[webknjaz]

Feel free to create a PR and invite @asvetlov to give more feedback on it.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new