extends + additionalProperties doesn't seem supported about json-schema-validator

[fge]

You are yet another victim of the misunderstanding of how extends works ;)

extends adds constraints to a schema, it does not make any attempts to merge schemas at all.

Both of your schemas expect an object instance. So far so good.

The first schema forbids any other members than "foo" to be present, so, when it see "bar", it complains -- rightfully so.

And the second schema forbids any other members than "bar" to be present, so, when it see "foo", it complains -- rightfully so as well.

This is not a bug: this is how it is supposed to work. And this is why the next proposed specification replaces extends with allOf, which has the same meaning, without the ambiguities. With allOf, your schema becomes:

{
    "allOf": [
        {
            "properties": {
                "foo": {
                    "type": "string"
                }
            },
            "additionalProperties": false
         },
         {
            "properties": {
                "bar": {
                    "type": "string"
                }
            },
            "additionalProperties": false
        }
    ]
}

[bpfoster]

Doh, well sorry for polluting your tracker then.
Based on that, is there no way using the current spec to accomplish what I'm describing here (instance of A to allow both "foo" and "bar", but an instance of B to only allow "bar")? I love the reuse that $ref gives me, but it sounds like I can't utilize that if I want to restrict the additional properties?

[fge]

Doh, well sorry for polluting your tracker then.

No problem... Actually, it is a recurring demand, and JSON Schema currently has no mechanism for that :/ And given the set of current keywords, I don't see how this is possible.

Last time someone had this problem on the group, I suggested that he just ignored properties he didn't want instead of using additionalProperties... I know of no way to achieve what you want. What would actually be needed is indeed schema merging, and it leads to a whole new class of problems!

[bpfoster]

Ok, thanks! If it's possible to bring something like this in for consideration on the spec, I would certainly love to see it!