Question: Json-schema evolution always not compatible with earlier version

[tatitati]

Hi people, thanks for this cool tool. Is awesome. I'm trying to use json-schemas for my developments, however I'm having something that still I don't understand:

I'm trying to do a very basic json-schema evolution: From this:

{
  "$id": "http://example.com/myURI.schema.json",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "properties": {
    "myField1": {
      "type": "integer"
    }
  },
  "required": ["myField1"],
  "type": "object"
}

To this new version, which adds another field "myField2", but is not required.

{
  "$id": "http://example.com/myURI.schema.json",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "properties": {
    "myField1": {
      "type": "integer"
    },
    "myField2": {
      "type": "integer", 
      "default": 0
    }
  },
  "required": [
    "myField1"
  ],
  "type": "object"
}

However I have always in schema registry UI:

Schema being registered is incompatible with an earlier schema

Am I missing something?

[rayokota]

You need to specify "additionalProperties": false on the original schema. That is because otherwise the first schema can accept JSON documents with "myField2": "foo" which would not be compatible with the second schema.

[big-andy-coates]

I ran into the same issue. In fact, if you're looking for full compatibility then you're out of luck. While it's technically possible to add and remove optional properties with full compatibility checks, there are some serious hoops to jump through. This makes it, IMHO, not workable as a solution.

I've detailed my findings in a quick post, the second part of which proposes a more user friendly approach to implementing JSON Schema compatibility checks.

I've raised #2927 to get feedback and look at the potential of including this in the Schema Registry.