Better documentation on extending RefResolver

[foxx]

The documentation made it quite difficult to understand how RefResolver should be extended, and I had to trawl through code to make it work. This is useful when you want to reference other schemas, but you don't want to use file://

It would be nice to see better documentation on this, but in the mean time, here is how I got it working for anyone who runs into the same problem;

import jsonschema

class SchemaResolver(jsonschema.RefResolver):
    def resolve_remote(self, uri):
        if uri.startswith('/SOMETHING'):
            # your custom schema goes here
            return {}
        else:
            # fallback to original
            return super(SchemaResolver, self).resolve_remote(uri)

def validate(schema, doc):
    """Validate using custom resolver"""
    resolver = SchemaResolver.from_schema(schema)
    validator_cls = jsonschema.validators.validator_for(schema)
    validator_cls.check_schema(schema)
    validator = validator_cls(schema, resolver=resolver)
    validator.validate(doc)

schema = {"$ref": "/SOMETHING/v1/definitions.json"}
doc = {"field": "value"}

validate(schema, doc)

[Julian]

Hey!

This is a duplicate of #135, but yes you're certainly right, documentation would be great here, would be awesome if you could write up what you've found possibly?

For your specific solution, jsonschema doesn't encourage (or explicitly support) inheritance for RefResolver (or really any of its APIs) -- I suspect you'll find other "solutions" for relative file references in that issue ticket, but it's certainly something that comes up enough to warrant some more direction.

Thanks!

[foxx]

Thanks for the quick reply, sorry I didn't see #135 previously. I'll have a read through and leave my thoughts, thanks again :)

[foxx]

I was able to find an alternative way to support this on 2.4.0 without needing to subclass. Either works fine, admittedly you have more customisation control if you subclass, but this is more readable and forces you to use correctly formed URIs

#!/usr/bin/env python

import jsonschema
import json

rootschema = json.load("""
{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "definitions": {
      "link": {
        "type": "number"
      }
    }
}
""")

schema = json.load("""
{
  "type": "object",
  "properties": {
    "field": { "$ref": "/v1/rootschema.json#/definitions/link" }
  }
}
""")

doc = json.load("""
{
    "field": 0
}
""")

validator_cls = jsonschema.validators.validator_for(schema)
validator_cls.check_schema(schema)
validator = validator_cls(schema)

validator.resolver.store['/v1/rootschema.json'] = rootschema
validator.validate(doc)

[ksolie]

@foxx Were you able to find a solution using Registry?