Ignore other properties when $ref is present

[gazpachoking]

According to the json reference spec, we should ignore all other properties when $ref is present. Currently we validate them all anyway.

[Julian]

Not saying we shouldn't do this as an optimization, but doesn't it say something like "when ref is encountered", which sounded like it meant whenever you happen to see the reference while you are validating that schema?

[gazpachoking]

I was thinking of this line

Any members other than "$ref" in a JSON Reference object SHALL be ignored.

From here: http://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03

[Julian]

That line governs JSON Reference. It means that if you're resolving JSON References you shouldn't fail to resolve because the reference has other members.

The relevant line covering what to do when validating JSON Schemas is:

When a validator encounters this attribute, it SHOULD replace the current schema with the schema referenced by the value's URI (if known and available) and re- validate the instance.

From http://tools.ietf.org/html/draft-zyp-json-schema-03#section-5.28

[gazpachoking]

Hmm, draft 4 just says:

JSON Schema uses JSON Reference [json‑reference] as a mechanism for schema addressing.

[gazpachoking]

Oh, and the 're- validate the instance' bit from draft 3 implies that any of the keywords you have already validated should be thrown out.

[Julian]

I don't think that means anything has changed, it just means either it was
left out accidentally or deemed unnecessary.

I'm also not sure that the intent of "re-validate" is to throw out what was
already seen, if it meant that out should have just mandated ignoring
everything but ref and said exactly those words.

Either way, if you want to add the pre-check I'm fine with that, since from
my standpoint even if allowing validating the other stuff is allowed, it's
not mandated and isn't something someone writing a schema should at all be
relying on, so it's a reasonable (although probably small) optimization.

Hmm, draft 4 just says:

JSON Schema uses JSON Reference [json‑reference] as a mechanism for schema
addressing.

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[gazpachoking]

Yeah, I think ultimately there aren't going to be any schemas that have stuff other than the $ref, unless they are written wrong, so it doesn't much matter. But I think @fge has also mentioned the intent of the spec was for other properties to be ignored when $ref is present.