Customizable refactor of draft-07 meta-schema

schema.json

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "http://example.com/my-custom-draft-07/schema#",
  "title": "Core schema meta-schema",

  "allOf": [{ "$ref": "#/definitions/schema" }],
  "$comment": "Add constraints here that should only apply to root schemas and not sub-schemas",

  "definitions": {
    "schema": {
      "$comment": "Add constainsts here that should apply to any schema including sub-schemas",

      "type": ["object", "boolean"],
      "properties": {
        "$id": {
          "type": "string",
          "format": "uri-reference"
        },
        "$schema": {
          "type": "string",
          "format": "uri"
        },
        "$ref": {
          "type": "string",
          "format": "uri-reference"
        },
        "$comment": {
          "type": "string"
        },
        "title": {
          "type": "string"
        },
        "description": {
          "type": "string"
        },
        "default": true,
        "readOnly": {
          "type": "boolean",
          "default": false
        },
        "writeOnly": {
          "type": "boolean",
          "default": false
        },
        "examples": {
          "type": "array",
          "items": true
        },
        "multipleOf": {
          "type": "number",
          "exclusiveMinimum": 0
        },
        "maximum": {
          "type": "number"
        },
        "exclusiveMaximum": {
          "type": "number"
        },
        "minimum": {
          "type": "number"
        },
        "exclusiveMinimum": {
          "type": "number"
        },
        "maxLength": { "$ref": "#/definitions/nonNegativeInteger" },
        "minLength": { "$ref": "#/definitions/nonNegativeIntegerDefault0" },
        "pattern": {
          "type": "string",
          "format": "regex"
        },
        "additionalItems": { "$ref": "#/definitions/schema" },
        "items": {
          "anyOf": [
            { "$ref": "#/definitions/schema" },
            { "$ref": "#/definitions/schemaArray" }
          ],
          "default": true
        },
        "maxItems": { "$ref": "#/definitions/nonNegativeInteger" },
        "minItems": { "$ref": "#/definitions/nonNegativeIntegerDefault0" },
        "uniqueItems": {
          "type": "boolean",
          "default": false
        },
        "contains": { "$ref": "#/definitions/schema" },
        "maxProperties": { "$ref": "#/definitions/nonNegativeInteger" },
        "minProperties": { "$ref": "#/definitions/nonNegativeIntegerDefault0" },
        "required": { "$ref": "#/definitions/stringArray" },
        "additionalProperties": { "$ref": "#/definitions/property-schema" },
        "definitions": {
          "type": "object",
          "additionalProperties": { "$ref": "#/definitions/schema" },
          "default": {}
        },
        "properties": {
          "type": "object",
          "additionalProperties": { "$ref": "#/definitions/property-schema" },
          "default": {}
        },
        "patternProperties": {
          "type": "object",
          "additionalProperties": { "$ref": "#/definitions/property-schema" },
          "propertyNames": { "format": "regex" },
          "default": {}
        },
        "dependencies": {
          "type": "object",
          "additionalProperties": {
            "anyOf": [
              { "$ref": "#/definitions/schema" },
              { "$ref": "#/definitions/stringArray" }
            ]
          }
        },
        "propertyNames": { "$ref": "#/definitions/schema" },
        "const": true,
        "enum": {
          "type": "array",
          "items": true,
          "minItems": 1,
          "uniqueItems": true
        },
        "type": {
          "anyOf": [
            { "$ref": "#/definitions/simpleTypes" },
            {
              "type": "array",
              "items": { "$ref": "#/definitions/simpleTypes" },
              "minItems": 1,
              "uniqueItems": true
            }
          ]
        },
        "format": { "type": "string" },
        "contentMediaType": { "type": "string" },
        "contentEncoding": { "type": "string" },
        "if": { "$ref": "#/definitions/schema" },
        "then": { "$ref": "#/definitions/schema" },
        "else": { "$ref": "#/definitions/schema" },
        "allOf": { "$ref": "#/definitions/schemaArray" },
        "anyOf": { "$ref": "#/definitions/schemaArray" },
        "oneOf": { "$ref": "#/definitions/schemaArray" },
        "not": { "$ref": "#/definitions/schema" }
      },
      "default": true
    },

    "property-schema": {
      "allOf": [{ "$ref": "#/definitions/schema" }],

      "$comment": "Add constraints here that should only apply to property sub-schemas"
    },

    "schemaArray": {
      "type": "array",
      "minItems": 1,
      "items": { "$ref": "#/definitions/schema" }
    },

    "nonNegativeInteger": {
      "type": "integer",
      "minimum": 0
    },

    "nonNegativeIntegerDefault0": {
      "allOf": [
        { "$ref": "#/definitions/nonNegativeInteger" },
        { "default": 0 }
      ]
    },

    "simpleTypes": {
      "enum": [
        "array",
        "boolean",
        "integer",
        "null",
        "number",
        "object",
        "string"
      ]
    },

    "stringArray": {
      "type": "array",
      "items": { "type": "string" },
      "uniqueItems": true,
      "default": []
    }
  }
}

This is a refactored version of the Draft-07 meta-schema. It doesn't do anything more or less that the official meta-schemas, but it's structured in a way that that makes it easier to add constraints for different parts of the schema. There is a space for contraints that should apply globally, constraints that should only apply to the root schema, and constraints that should only apply to property sub-schemas. If you are taking on the task of writing a custom draft-07 meta-schema, this is a good place to start.