json-schema-faker/src/core/infer.js

JSON-Schema + fake data generators

const inferredProperties = {
  array: [
    'additionalItems',
    'items',
    'maxItems',
    'minItems',
    'uniqueItems',
  ],
  integer: [
    'exclusiveMaximum',
    'exclusiveMinimum',
    'maximum',
    'minimum',
    'multipleOf',
  ],
  object: [
    'additionalProperties',
    'dependencies',
    'maxProperties',
    'minProperties',
    'patternProperties',
    'properties',
    'required',
  ],
  string: [
    'maxLength',
    'minLength',
    'pattern',
    'format',
  ],
};

inferredProperties.number = inferredProperties.integer;

const subschemaProperties = [
  'additionalItems',
  'items',
  'additionalProperties',
  'dependencies',
  'patternProperties',
  'properties',
];

/**
 * Iterates through all keys of `obj` and:
 * - checks whether those keys match properties of a given inferred type
 * - makes sure that `obj` is not a subschema; _Do not attempt to infer properties named as subschema containers. The
 * reason for this is that any property name within those containers that matches one of the properties used for
 * inferring missing type values causes the container itself to get processed which leads to invalid output. (Issue 62)_
 *
 * @returns {boolean}
 */
function matchesType(obj, lastElementInPath, inferredTypeProperties) {
  return Object.keys(obj).filter(prop => {
    const isSubschema = subschemaProperties.indexOf(lastElementInPath) > -1;
    const inferredPropertyFound = inferredTypeProperties.indexOf(prop) > -1;

    if (inferredPropertyFound && !isSubschema) {
      return true;
    }

    return false;
  }).length > 0;
}

/**
 * Checks whether given `obj` type might be inferred. The mechanism iterates through all inferred types definitions,
 * tries to match allowed properties with properties of given `obj`. Returns type name, if inferred, or null.
 *
 * @returns {string|null}
 */
function inferType(obj, schemaPath) {
  const keys = Object.keys(inferredProperties);

  for (let i = 0; i < keys.length; i += 1) {
    const typeName = keys[i];
    const lastElementInPath = schemaPath[schemaPath.length - 1];

    if (matchesType(obj, lastElementInPath, inferredProperties[typeName])) {
      return typeName;
    }
  }
}

export default inferType;