Do not restrict +json media type suffix to application/

[scop]

What do these changes do?

Fix +json media type suffix handling to apply to other main types besides application/.

An example of a registered media type triggering this issue is https://www.iana.org/assignments/media-types/model/gltf+json

Are there changes in behavior for the user?

Media types with main type other than application using the '+json` suffix are accepted as JSON now.

Related issue number

Checklist

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• Unit tests for the changes exist
• Documentation reflects the changes
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[codecov]

Codecov Report

Merging #5894 (b0eaa72) into master (ae23fd6) will decrease coverage by 0.84%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5894      +/-   ##
==========================================
- Coverage   96.75%   95.90%   -0.85%     
==========================================
  Files          44      102      +58     
  Lines        9851    31442   +21591     
  Branches     1591     3218    +1627     
==========================================
+ Hits         9531    30155   +20624     
- Misses        182     1099     +917     
- Partials      138      188      +50     

Flag	Coverage Δ
unit	95.82% <100.00%> (-0.83%)	⬇️

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

Impacted Files	Coverage Δ
aiohttp/helpers.py	97.67% <100.00%> (+0.84%)	⬆️
tests/test_helpers.py	98.87% <100.00%> (ø)
aiohttp/client.py	77.27% <0.00%> (-16.72%)	⬇️
aiohttp/resolver.py	84.12% <0.00%> (-9.21%)	⬇️
aiohttp/http_writer.py	97.35% <0.00%> (-1.78%)	⬇️
aiohttp/connector.py	94.85% <0.00%> (-1.66%)	⬇️
aiohttp/web_app.py	97.00% <0.00%> (-0.34%)	⬇️
aiohttp/typedefs.py	100.00% <0.00%> (ø)
aiohttp/web_middlewares.py	100.00% <0.00%> (ø)
tests/test_web_request_handler.py	97.56% <0.00%> (ø)
... and 68 more

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[asvetlov]

Sorry, I think that the PR should be rejected.
There is no guarantee that the content type like xxx/yyy+json is fully JSON compatible.

If in your particular case model/gltf+json can be processed by .json() call -- pass the content type explicitly:
await resp.json(content_type="model/gltf+json").

[scop]

Can you cite a reference that says +json might not be JSON compatible? The suffix registration is not restricted to the application/ main type.

https://www.rfc-editor.org/rfc/rfc6839.html#section-3.1 says:

The suffix "+json" MAY be used with any media type whose representation follows that established for "application/json".

Additionally, from https://www.rfc-editor.org/rfc/rfc6839.html#section-2

At the same time, using the suffix allows receivers of the media
types to do generic processing of the underlying representation in
cases where

 they do not need to perform special handling of the particular
 semantics of the exact media type, and

 there is no special knowledge needed by such a generic processor
 in order to parse that underlying representation other than what
 would be needed to parse any example of that underlying
 representation.

This is exactly the case for aiohttp.

I think that's guarantee enough, as much as there is guarantee that anything served as application/json is JSON compatible (there is no guarantee about that either, but both that and +json are reasonable expectations).

[asvetlov]

Thank you for clarification.
Let's keep the PR open until I re-read the mentioned RFC

[asvetlov]

I've changed my mind, the PR is correct.
Thanks!

[patchback]

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

❌ Failed to cleanly apply a82d289 on top of patchback/backports/3.8/a82d2892dbe1266f248362725be0bb338069fbf7/pr-5894

Backporting merged PR #5894 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/3.8/a82d2892dbe1266f248362725be0bb338069fbf7/pr-5894 upstream/3.8

4. Now, cherry-pick PR Do not restrict +json media type suffix to application/  #5894 contents into that branch:

   $ git cherry-pick -x a82d2892dbe1266f248362725be0bb338069fbf7

   If it'll yell at you with something like fatal: Commit a82d2892dbe1266f248362725be0bb338069fbf7 is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x a82d2892dbe1266f248362725be0bb338069fbf7

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Do not restrict +json media type suffix to application/  #5894 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.8/a82d2892dbe1266f248362725be0bb338069fbf7/pr-5894

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.

[aio-libs-github-bot]

💔 Backport was not successful

The PR was attempted backported to the following branches:

• ❌ 3.8: Commit could not be cherrypicked due to conflicts

[asvetlov]

Sorry, the backporting is very hard since previous pull requests that introduced and updated json_re were not backported too.