Ascola/add handler type aliases

[AustinScola]

What do these changes do?

• Add a request handler type alias aiohttp.typedefs.Handler
• Use the Handler type alias in other parts of the package

Are there changes in behavior for the user?

Users can now use the type alias to annotate their code.

Related issue number

Issue #4686

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[Dreamsorcerer]

If you could have a quick search for places in the examples and tests where this annotation can be used, that would suffice for test coverage (as messing up the type would cause a mypy error in the example code).

A couple of locations that look good:

aiohttp/examples/web_rewrite_headers_middleware.py

Line 16 in 09ac1cb

async def middleware(request: web.Request, handler: _WebHandler) -> web.StreamResponse:

aiohttp/tests/test_web_middleware.py

Line 14 in 09ac1cb

async def middleware(request, handler):

[codecov]

Codecov Report

Merging #5847 (a00d2f9) into master (d55728d) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5847      +/-   ##
==========================================
- Coverage   96.75%   96.75%   -0.01%     
==========================================
  Files          44       44              
  Lines        9849     9848       -1     
  Branches     1591     1591              
==========================================
- Hits         9529     9528       -1     
  Misses        182      182              
  Partials      138      138              

Flag	Coverage Δ
unit	96.64% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiohttp/web_app.py	97.33% <ø> (ø)
aiohttp/typedefs.py	100.00% <100.00%> (ø)
aiohttp/web_middlewares.py	100.00% <100.00%> (ø)
aiohttp/web_routedef.py	98.11% <100.00%> (-0.02%)	⬇️
aiohttp/web_urldispatcher.py	97.83% <100.00%> (-0.01%)	⬇️

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[Dreamsorcerer]

Looks good to me. Hopefully someone else can take a quick look as well and approve.

[greshilov]

LGTM! Reasonable change, since typing in python becomes more and more common.

P.S. Maybe Middleware object deserves its public type alias too.

_Middleware = Union[
    Callable[[Request, Handler], Awaitable[StreamResponse]],
    Callable[["Application", Handler], Awaitable[Handler]],  # old-style
]

[patchback]

Backport to 3.8: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 1b45c73 on top of patchback/backports/3.8/1b45c733f07d59f9f56cf468b39cec109f745ff8/pr-5847

Backporting merged PR #5847 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git add remote upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.8/1b45c733f07d59f9f56cf468b39cec109f745ff8/pr-5847 upstream/3.8

4. Now, cherry-pick PR Ascola/add handler type aliases #5847 contents into that branch:

   $ git cherry-pick -x 1b45c733f07d59f9f56cf468b39cec109f745ff8

   If it'll yell at you with something like fatal: Commit 1b45c733f07d59f9f56cf468b39cec109f745ff8 is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x 1b45c733f07d59f9f56cf468b39cec109f745ff8

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Ascola/add handler type aliases #5847 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.8/1b45c733f07d59f9f56cf468b39cec109f745ff8/pr-5847

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[webknjaz]

@AustinScola @Dreamsorcerer could you backport this manually per the bot comment above?

[AustinScola]

@AustinScola @Dreamsorcerer could you backport this manually per the bot comment above?

Sure thing

[AustinScola]

Fixed the conflicts for the backport and made PR #5861.