MergeAdditionalProperties and JSON Schema spec

[Allam76]

According to here: "Schema inheritance", the following is true:

JSON Schema doesn't use an object oriented paradigm, so concepts like inheritance don't translate well. JSON Schema is a collection of constraints. It's subtractive rather than additive like most people are used to. This means that given an empty schema, the set of valid JSON documents is the set of all JSON documents. As you add keywords, you are subtracting from the set of valid JSON documents. Once something is removed from the set, it can't be added back in.

This means that for instance enums: from a subschema, instead as beeing merged with the enums of the base schema, they should restrict the base schema. This is obviously not what lodash merge does and if desired, requires some additional logic.

If people already use mergeAdditionalProperties, maybe another option could be used?
Also beware, combining two schema is apparently against the philosophy of JSON schema.

I'll take a look and come back.
#17
#18

[Allam76]

Ok I solved this by lodash.mergeWith. Assuming that all arrays in the schema should be overwritten, I copied from here.
I added another option: restrictWithAdditionalProperties and code:

//// Below mergeAdditionalProperties
          if(options.restrictWithAdditionalProperties){
            delete node.$ref
            newValue = _.mergeWith(newValue, node, mergeCopyArrays)
          }

and

function mergeCopyArrays(objValue, srcValue) {
  if (Array.isArray(objValue)) {
    return srcValue;
  }
}

This is obviously a too simple solution to be used as-is in the framework but it handles my use case. For a more mature solution, I believe the options have to be refined. One could imagine going through the JSON Schema Spec and add all relevant cases.

Feel free to close this if out of scope...
Cheers
Martin