json_ schema

May 24, 2014

After a few primitive attempts at developing some basic JSON Schema validation systems for Committee, I finally mustered a bit of initiative and developed a fully spec-compliant schema and hyper-schema validator which I’ve officially released as json_schema).

During a validation, json_schema will build JSON Pointers to any data that failed, and to the exact schema rule that failed it. This is designed to help with the validation debugging process:

schema.json#/properties: failed schema #/properties/properties: Expected data to be of type "object"; value was: [].

schema.json#: failed schema #: Data did not match all subschemas of "allOf" condition.

I tried to pay special attention to the more difficult features that weren’t well covered by my previous implementations like self-referencing schemas, tuple validation in items, schema dependencies, along with a multitude of other things.

Besides validation, json_schema should also provide a nice way to introspect and traverse schemas programmatically. Committee’s already been reworked to use it, and I hope to soon start moving over other Interagent projects.

A final thought: there is no better way to understand a spec than to write an implementation for it. I thought that I had an okay understanding the V4 JSON Schema spec before starting the project, but then as you might expect, I ran into every mental grey area, gap in understanding, obscure feature, and special case. I now realize just how tenuous my understanding actually was.

Check it out on GitHub.

json_ schema was published on May 24, 2014.

Find me on Twitter at @brandur.

Did I make a mistake? Please consider sending a pull request.