REST API: Allow arrays to be sent as CSVs

[pento]

After #38531, it'd be helpful if arrays could be sent as CSVs.

Related: #38553, #38577, #38579.

[pento]

In 39048:

REST API: Allow parameters defined as array to be sent as CSVs.

This allows parameters that are often handled as CSVs to be properly parsed.

Fixes #38586.

[rmccue]

This needs to be documented further, and we should check whether this is the best way to implement it. Right now, there's no hint to the client that "array" means you can send CSV as well. Potentially, using JSON Schema's anyOf would be better here.

[pento]

I'm cool with whatever option. Everywhere endpoint parameters have the type array, we also want to allow CSV.

Actually, I'd be fine with just documenting that, and leaving it, particularly as changing the type in the endpoint docs will be confusing. Apps that care about JSON Schema can send actual arrays, apps that don't can send either.

[rmccue]

I'm OK with that too, so long as it's documented. If we can come up with a standard, self-documenting way though, probably best to do that.

[TimothyBlynJacobs]

I would really like to see anyOf or oneOf, etc. being used. Currently I'm going to need to add my own validation callbacks for handling those more complex schema, but it'd be great if something like that is handled in core.

[pento]

Updating ​schema.html to say "array or CSV" will do the job, but I don't know what the plan is for merging the API docs to devhub.

[joehoyle]

Hmm I'm not too keen on this approach, and I think this was committed without too much consideration to different types etc. It appears this would also need a modification to the sanitizer also, as right now, it doesn't look like this is doing both validation and sanitization.

Just because the value isn't an array doesn't mean we can pass it to preg_split, what if it's other types?

[joehoyle]

In 39061:

REST API: Sanitize arrays being sent as CSVs.

In #38586 the ability to parse arrays as csv was introduced, however it didn't add any support for validating csv arrays. This adds such sanitization, and also a good amount of unit tests for all sanitization baed off schema.

See #38586.

[joehoyle]

In #38617 I audited all the endpoints to make sure we are using array / type combos wherever we can. These all support CSVs by default now, thanks to this ticket - given we haven't run into any issues in all those instances I think it's safe to say this was a good thing to do so I'm closing it out.

[SergeyBiryukov]

In 44703:

Build/Test Tools: Correct WP_Test_REST_Schema_Sanitization::test_type_string() to check for both 1.1 float and '1.10' string explicitly.

Previously, the test only passed due to a bug in PHPUnit 7.1.x and older versions.

Fixes #43218. See #38586.