blockly/core/field_registry.ts

/**
 * @license
 * Copyright 2019 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @fileoverview Fields can be created based on a JSON definition. This file
 *    contains methods for registering those JSON definitions, and building the
 *    fields based on JSON.
 */

/**
 * Fields can be created based on a JSON definition. This file
 *    contains methods for registering those JSON definitions, and building the
 *    fields based on JSON.
 * @namespace Blockly.fieldRegistry
 */
import * as goog from '../closure/goog/goog.js';
goog.declareModuleId('Blockly.fieldRegistry');

import type {Field} from './field.js';
import type {IRegistrableField} from './interfaces/i_registrable_field.js';
import * as registry from './registry.js';


/**
 * Registers a field type.
 * fieldRegistry.fromJson uses this registry to
 * find the appropriate field type.
 * @param type The field type name as used in the JSON definition.
 * @param fieldClass The field class containing a fromJson function that can
 *     construct an instance of the field.
 * @throws {Error} if the type name is empty, the field is already registered,
 *     or the fieldClass is not an object containing a fromJson function.
 * @alias Blockly.fieldRegistry.register
 */
export function register(type: string, fieldClass: IRegistrableField) {
  registry.register(registry.Type.FIELD, type, fieldClass);
}

/**
 * Unregisters the field registered with the given type.
 * @param type The field type name as used in the JSON definition.
 * @alias Blockly.fieldRegistry.unregister
 */
export function unregister(type: string) {
  registry.unregister(registry.Type.FIELD, type);
}

/**
 * Construct a Field from a JSON arg object.
 * Finds the appropriate registered field by the type name as registered using
 * fieldRegistry.register.
 * @param options A JSON object with a type and options specific to the field
 *     type.
 * @return The new field instance or null if a field wasn't found with the given
 *     type name
 * @alias Blockly.fieldRegistry.fromJson
 * @internal
 */
export function fromJson(options: AnyDuringMigration): Field|null {
  return TEST_ONLY.fromJsonInternal(options);
}

/**
 * Private version of fromJson for stubbing in tests.
 */
function fromJsonInternal(options: AnyDuringMigration): Field|null {
  const fieldObject =
      registry.getObject(registry.Type.FIELD, options['type']) as
          IRegistrableField |
      null;
  if (!fieldObject) {
    console.warn(
        'Blockly could not create a field of type ' + options['type'] +
        '. The field is probably not being registered. This could be because' +
        ' the file is not loaded, the field does not register itself (Issue' +
        ' #1584), or the registration is not being reached.');
    return null;
  }
  return fieldObject.fromJson(options);
}

export const TEST_ONLY = {
  fromJsonInternal,
}