JsonSchema - Should have one of two properties

Question

I'm trying to create a schema for the config file that supports Gaspar.

At the root of the object you need to specify at least one of Models and Controllers (or both).

I found this: https://stackoverflow.com/a/31841897/404459 which seems to answer the question, and gives me something like this (Model and Controllers are really complex objects, but this simplified version proves the point):

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "type": "object",
    "anyOf": [
        {
            "required": [
                "Models"
            ]
        },
        {
            "required": [
                "Controllers"
            ]
        }
    ],
    "properties": {
        "Models": {
            "type": "string"
        },
        "Controllers": {
            "type": "string"
        },
        "IgnoreAnnotations": {
          "type": "boolean"
        }
    }
}

This all works well and validates in VS Code, but it fails strict validation using the https://www.schemastore.org/json/ validator, which returns:

################ Error message
>> compile              | schemas/json/gaspar.json (draft-07)(FullStrictMode)
>> Error: strict mode: required property "Models" is not defined at "https://json.schemastore.org/gaspar.json#/anyOf/0" (strictRequired)
##############################

I've tried moving the properties inside the anyOf, but it opens up more issues than it solves; maybe that's the right approach but needs more stuff than I'm aware of.

How can I get this to pass strict validation and work?

Answer 1

Adding minProperties: 1 with the anyOf array of required schemas provides the constraint needed to choose at least one of the required properties and any other optional property.

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "anyOf": [
    {
      "required": [
        "Models"
      ]
    },
    {
      "required": [
        "Controllers"
      ]
    }
  ],
  "minProperties": 1,
  "properties": {
    "Models": {
      "type": "string"
    },
    "Controllers": {
      "type": "string"
    },
    "IgnoreAnnotations": {
      "type": "boolean"
    }
  }
}

Passing instances

{
  "Models": ""
}

{
  "Controllers": ""
}

{
  "Models": "",
  "IgnoreAnnotations": true
}

{
  "Controllers": "",
  "IgnoreAnnotations": true
}

{
  "Models": "",
  "Controllers": "",
  "IgnoreAnnotations": true
}

Failing instances

{
  "IgnoreAnnotations": true
}

{
  "Test": ""
}

EDIT: To add this type of schema to schemastore.org following the contribution guidelines and their use of Ajv strict mode. You can re-write this schema as follows:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "anyOf": [
    {
      "type": "object",
      "required": [
        "Models"
      ],
      "minProperties": 1,
      "properties": {
        "Models": {
          "type": "string"
        },
        "IgnoreAnnotations": {
          "type": "boolean"
        }
      }
    },
    {
      "type": "object",
      "required": [
        "Controllers"
      ],
      "minProperties": 1,
      "properties": {
        "Controllers": {
          "type": "string"
        },
        "IgnoreAnnotations": {
          "type": "boolean"
        }
      }
    }
  ]
}