Schema validation should not clear cache

[windlass]

It looks like $ref schemas are not useable when schema validation is enabled. The following schema is valid, but is only useable to validate documents if schema validation is disabled:

{ 
  "type": "object"
  "definitions": {
    "test": {
      "type": "string"
    }
  },
  "properties": {
    "foo": { "$ref": "#/definitions/test" }
  }
}

The problem seems to be that when validated with :validate_schema, the schema is first validated. Then, the cache is cleared, which has a side-effect of removing the schema for #/definitions/test as well has the schemas for schema itself. Then, when you validate a document against it the $ref fails to resolve.

One easy workaround for this (but not necessarily the right fix) would be to turn schema caching on before validating:

JSON::Validator.cache_schemas = true

This causes the cache to be retained between validating the schema and the data, so the $ref URI resolves. But since this is probably the desired behavior whenever doing a schema validation plus a validation against the schema, it's probably better to implicitly set @@cache_schemas = true when schema validation is requested.

[windlass]

It occurs to me that another approach may be to retain the current caching behavior, but to selectively purge the cache of the "schema schemas"; i.e. the ones used to validate the schema itself, after validating the schema.

[dkowis]

More interestingly, this doesn't happen all the time.

The full schema from http://json-schema.org/example2.html doesn't fail the $ref resolving problem.

[hoxworth]

This should be fixed in 2.1.9. Clearing of the schema cache will become a validation option, which will explicitly be set to false for schema validation. The old cache_schemas= method will be deprecated and removed in a future version.