json-schema 2.0.1 broke schema validation

[dazza-codes]

The full validation broke with v2.0.1 when it was fine with v2.0.0, for example:

### BEGIN JSON SCHEMA RUBY CODE
 PAGE_SCHEMA = <<-END_SCHEMA
  {
    "type": "object",
    "title": "page",
    "description": "A Resource Index page of results.",
    "additionalProperties": false,
    "properties": {
      "page": { "type": "number", "required": true },
      "pageCount": { "type": "number", "required": true },
      "prevPage": { "type": ["number","null"], "required": true },
      "nextPage": { "type": ["number","null"], "required": true },
      "links": { "type": "object", "required": true },
      "collection": { "type": "array", "required": true }
    }
  }
  END_SCHEMA
### END JSON SCHEMA RUBY CODE

The validation error reads: "JSON::Schema::ValidationError: The property '#/properties/page/required' of type TrueClass did not match the following type: array in schema http://json-schema.org/draft-04/schema#"

This can't be right for a "required" property, surely?

[hoxworth]

The major version change from 1.x to 2.x was made due to the breaking changes introduced in JSON Schema Draft-04 with respect to a number of properties. Since Draft-04 is final, this library now uses it as the default validator when the specific version is not specified. The usage of the required keyword did change in Draft-04, and thus validation is failing.

Draft-03 support is still provided, so existing schemas can validate against Draft-03 through a variety of methods. The simplest and most portable way of doing this is to use the $schema keyword in your schema and set it to draft-03, as follows:

PAGE_SCHEMA <<-END_SCHEMA
  {
    "$schema": "http://json-schema.org/draft-03/schema#",
    "type": "object",
    "title": "page",
    ...
  }
END_SCHEMA

Alternatively, you can specify the draft-03 validator from the validation call, if you cannot or do not want to edit your schema itself.

JSON::Validator.validate(schema, data, :version => :draft3)

I know this is a frustrating change, and I'm not exactly sure what the right approach is to ensure backwards compatibility. My supposition is that since JSON Schema is still in draft 4 and is (slowly) changing, the best we can do with this library is give users the ability to lock to specific schema versions while updating the major version number whenever a new breaking change occurs in a published draft.

For reference, the following link outlines changes from draft-03 to draft-04, if you are interested in some of the updates: https://github.com/json-schema/json-schema/wiki/ChangeLog.

[hoxworth]

Closing this until a failure case can be presented with respect to schema versions.