Remove overlapping slots and fix broken slots inheritance

[ariebovenberg]

What do these changes do?

There were a few __slots__ related mistakes:

python -m slotscheck aiohttp -v
ERROR: 'aiohttp.web_protocol:RequestHandler' defines overlapping slots.
       - _reading_paused (aiohttp.base_protocol:BaseProtocol)
ERROR: 'aiohttp.web_response:StreamResponse' has slots but superclass does not.
       - aiohttp.helpers:CookieMixin

Fixing the second error was more problematic than it seems. The straightforward solution of adding __slots__ = ('_cookies', ) was not possible, because this triggered a TypeError: multiple bases have instance lay-out conflict in HTTPException since non-emptly slots cannot be combined with an Exception case class:

>>> class CookieMixin:
...  __slots__ = ('_cookies', )
...
>>> class HTTPException(CookieMixin, Exception):
...  pass
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: multiple bases have instance lay-out conflict

There are several possible solutions:

1. put empty slots in CookieMixin, since it's an abstract class. This is the currently implemented solution.
2. leave the situation as-is. The __slots__ in StreamResponse will be mostly ineffective.
3. remove __slots__ from StreamResponse. They aren't saving memory or preventing __dict__ from being created.

Are there changes in behavior for the user?

StreamResponse will no longer have a __dict__, so arbitrary attributes cannot be set. This is not documented, so likely not a problem

Related issue number

No issue. This is a small change.

Checklist

• I think the code is well written
• Unit tests for the changes exist n/a (see questions below)
• Documentation reflects the changes n/a
• 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."

Questions

• regarding tests: probably not needed. I discovered the slots issue with slotscheck, a tool I wrote. Of course, If you like, I can add it to tox/CI as I've done for instagram/LibCST and dry-python/returns.

[Dreamsorcerer]

Would be great if you could add this test to the linter step in CI. Then we can avoid introducing new overlaps in future.

[ariebovenberg]

@Dreamsorcerer You mean in workflows/ci.yaml?

    - name: Run linters
      run: |
        make mypy
        make slotscheck  # after adding slotscheck to Makefile

Alternatively I can add the hook to the .pre-commit-config.yaml. Whichever you prefer.

[Dreamsorcerer]

@Dreamsorcerer You mean in workflows/ci.yaml?

    - name: Run linters
      run: |
        make mypy
        make slotscheck  # after adding slotscheck to Makefile

That looks fine to me. Not sure it needs to go in the Makefile. But, I'd make it a separate step (and probably rename that existing step to 'Run Mypy'). I meant lint job earlier, rather than linter step..

[ariebovenberg]

That looks fine to me. Not sure it needs to go in the Makefile. But, I'd make it a separate step (and probably rename that existing step to 'Run Mypy'). I meant lint job earlier, rather than linter step.

Can do. I'm curious though: what's the reasoning behind what goes in pre-commit vs GitHub workflow?

[codecov]

Codecov Report

Merging #6547 (32ce395) into master (21aff1f) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #6547   +/-   ##
=======================================
  Coverage   93.36%   93.36%           
=======================================
  Files         104      104           
  Lines       30506    30509    +3     
  Branches     3068     3069    +1     
=======================================
+ Hits        28482    28485    +3     
  Misses       1850     1850           
  Partials      174      174           

Flag	Coverage Δ
unit	93.29% <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_protocol.py	88.31% <ø> (ø)
aiohttp/web_response.py	98.41% <ø> (ø)
aiohttp/helpers.py	96.94% <100.00%> (+<0.01%)	⬆️
tests/test_helpers.py	98.96% <100.00%> (+<0.01%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 21aff1f...32ce395. Read the comment docs.

[Dreamsorcerer]

That looks fine to me. Not sure it needs to go in the Makefile. But, I'd make it a separate step (and probably rename that existing step to 'Run Mypy'). I meant lint job earlier, rather than linter step.

Can do. I'm curious though: what's the reasoning behind what goes in pre-commit vs GitHub workflow?

Probably a question for someone else. I'd assume that pre-commit is being run as a git hook, so it makes sense to have primarily fast checks which are likely to catch mistakes. If it only catches an error for 1 in 500 PRs or something, it's probably best not delaying a developer's commit. But, not sure if that's what has been done so far, I didn't set up anything in pre-commit and don't really mind which way it goes in.

[ariebovenberg]

That looks fine to me. Not sure it needs to go in the Makefile. But, I'd make it a separate step (and probably rename that existing step to 'Run Mypy'). I meant lint job earlier, rather than linter step.

Can do. I'm curious though: what's the reasoning behind what goes in pre-commit vs GitHub workflow?

Probably a question for someone else. I'd assume that pre-commit is being run as a git hook, so it makes sense to have primarily fast checks which are likely to catch mistakes. If it only catches an error for 1 in 500 PRs or something, it's probably best not delaying a developer's commit. But, not sure if that's what has been done so far, I didn't set up anything in pre-commit and don't really mind which way it goes in.

Indeed, problems with slots probably won't occur in most PRs. I'll add it to the GH workflow for now.

[asvetlov]

Thanks!

[webknjaz]

@Dreamsorcerer @ariebovenberg does anybody remember why this never got backported to stable branches?

[patchback]

Backport to 3.15: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 65de218 on top of patchback/backports/3.15/65de218c6297284663eeae5c07e9146ef1e4485e/pr-6547

Backporting merged PR #6547 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 remote add 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/3.15/65de218c6297284663eeae5c07e9146ef1e4485e/pr-6547 upstream/3.15

4. Now, cherry-pick PR Remove overlapping slots and fix broken slots inheritance #6547 contents into that branch:

   $ git cherry-pick -x 65de218c6297284663eeae5c07e9146ef1e4485e

   If it'll yell at you with something like fatal: Commit 65de218c6297284663eeae5c07e9146ef1e4485e is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x 65de218c6297284663eeae5c07e9146ef1e4485e

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Remove overlapping slots and fix broken slots inheritance #6547 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.15/65de218c6297284663eeae5c07e9146ef1e4485e/pr-6547

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]

@Dreamsorcerer I think we need to figure this out: #13466