Json schema validation

[sorenbronsted]

Instead of implementing json schema validation there exists implementations for php out there in the wild. I will suggest using one of these instead of inventing the wheel once again :-)

[TimothyBlynJacobs]

Thanks for the ticket @sorenbronsted!

Did you have any libraries in mind?

Some things we need to consider:

1. Sanitization. Our schema implementation also supports sanitizing values. Are there any other json schema libraries that do this?
2. Translation. The libraries I've seen aren't very amenable to translating the error messages. They also often concatenate parts of different English strings together, which doesn't work for all languages.
3. Type conversion. We need to make sure things like are boolean checks behave the same way. Additionally we support csv syntax for arrays. This would need to be checked for all types.
4. v3 required syntax.
5. Our schema validators don't work on an entire schema for top level requests properties. So we'd need to transform those values into something the validator could work with.
6. Dependency size. Our schema validator is comparably small to the other PHP schema validators I've seen. We don't want to bring on a large dependency.

[TimothyBlynJacobs]

Closing per my latest comment. If something significantly changed around WP's attitude to including third party libraries, and we wanted to totally redo our schema validation, we could maybe take a look at this then. But I don't foresee this happening in the short-medium term.