Clone web request's state

[asvetlov]

Fix for #2284

[kxepal]

I hope there are no nested dicts/list in state, right?

[codecov-io]

Codecov Report

Merging #2287 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2287      +/-   ##
==========================================
+ Coverage   97.24%   97.24%   +<.01%     
==========================================
  Files          39       39              
  Lines        8094     8096       +2     
  Branches     1410     1411       +1     
==========================================
+ Hits         7871     7873       +2     
  Misses         97       97              
  Partials      126      126

Impacted Files	Coverage Δ
aiohttp/web_request.py	99.68% <100%> (ø)	⬆️

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[asvetlov]

It's impossible to perform deep state copy for an obvious reasons: values are not copyable very often, they could be an opened socket for example.

Thus we have 3 options:

1. Cleanup a state on copy.
2. Do swallow copy.
3. Share state between all copies.

I believe the option 2 is better than others.

[kxepal]

@asvetlov What's a case for req.clone()? May be we can make it immutable instead to do not any copies?

[asvetlov]

.clone() is intended to be used in middlewares:

@asyncio.coroutine
def middleware_factory(app, next_handler):
    @asyncio.coroutine
    def middleware(request):
        request2 = request.clone(rel_url="/new_url", method="GET")
        response = yield from next_handler(request2)
    return middleware

I'd like to extend clone() params for fixing #2171 too.

[kxepal]

Hm...I see. Then it seems swallow copy is the only option.

[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