You're right, this is for master.

Do we follow any RFC regarding the formatting of the json/xml/etc payloads?
If not, what about doing it? See #30559

Do we follow any RFC regarding the formatting of the json/xml/etc payloads?

Not really, I just copied the content format from TwigBundle exceptions.

If not, what about doing it? See #30559

Good idea! I'll check the RFC for each response format.

Later, I guess we should update the TwigBundle errors/exceptions as well.

Status: Needs Work

Status: Needs Review

This is ready so far, because we don't have more info from HttpException, but if we wanted to complete the spec details...

https://tools.ietf.org/html/rfc7807#section-3
The ability to convey problem-specific extensions allows more than one problem to be conveyed.

... we might need a meta argument containing standard (e.g. type, instance) and/or non-standard (e.g. balance, invalid-params, etc) meta-information about the error.

Ideally something like this:

throw new ProblemDetailsHttpException(400, 'Your request parameters didn't validate.', null, ['Content-Type' => 'application/problem+json'], 0, [
    'type' => 'https://example.net/validation-error',
    'invalid-params' => [ 
        [
            'name' => 'age',
            'reason' => 'must be a positive integer'
        ],
        [
            'name' => 'color',
            'reason' => 'must be green, red or blue'
        ],
    ],
]);

then, the last argument (named e.g. meta) could be handled by FlattenException and merge it into the final formatted content. WDYT?

@yceruto Thank you for working on this topic, which we should tackle. But I don't think this is the right approach. Let's talk about this this week-end during the Hackaton.

@fabpot then I guess should I close here, right?

No, we should talk first

As discussed, this code should be moved to a new component (maybe ErrorException) that could be used in both "prod" (where a Debug component doesn't make sense) and dev as hard dep of the HttpKernel component.

Later, the ExceptionListener can use it and also the Debug req can be moved to require-dev section in the future.

See #31065