Implement the custom format validator

[arjan]

See #50

[jonasschmidt]

Sounds like a great idea! I will have a look at the PR later today and give some feedback.

[arjan]

The potential issue I see with this solution that it's using the Application environment. Meaning that when two independent parts of the project use a custom format validator, they need to ensure that they reach agreement of the callback module to use.

A better solution would be to add an extra context argument to the validate call, which can carry this validator configuration all the way into the validation. This would also allow to put custom values in the context which then could be used in the validation callback. However, this would be a very large change, wiring that context argument through every function call.. so my proposal is maybe not ideal, but quite pragmatic.

[jonasschmidt]

Yes, good point. Another option would be to put the format validator in the %ExJsonSchema.Schema.Root{} struct that contains the resolved schema. One could argue that it's logically a part of the schema anyway, so it would fit there. That struct would only have to be passed to ExJsonSchema.Validator.Format.validate to make it available there.

[jonasschmidt]

So a great approach would be to (optionally) pass configuration options to ExJsonSchema.Schema.resolve and put them in the schema struct. The current logic could also stay there as a fallback, so the user has the choice of whether to define the format validator globally or per schema.

[coveralls]

Coverage increased (+0.01%) to 98.673% when pulling 9b9c758 on botsquad:custom-format-validator into 134b61a on jonasschmidt:master.

[arjan]

I force-pushed to remove my last commit which made the return value "nicer", so now the validator should return a list of errors again.

I agree that passing down a format validator inside the struct would be nice, but it's additional to this PR, I'll create a ticket for it after this is merged.

[jonasschmidt]

Ah, sorry, that was a misunderstanding. I prefer the version you had in the end, where the format validator function just returns a boolean. I should have phrased that comment a bit more clearly.

Any comments on the idea of putting the custom format validator in the schema struct?

[arjan]

Oh, hah, oops :-) Git reflog ftw, I've pushed again.

About the custom format validator, I think it could be stored in the %Root{} struct under an options key or whatever. And then pass this options down into the ExJsonSchema.Validator.validate_aspect function, which forwards it to each validator.

[arjan]

But like I said maybe it's better to do that in a separate PR.

[jonasschmidt]

Ok, that makes sense. I will merge and release the current state. Thank you for the excellent work 👍

[arjan]

Thanks!

[jonasschmidt]

Just released on Hex as well as version 0.7.0.