locale_plugin.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import {NodePath, PluginObj} from '@babel/core';
import {LogicalExpression, MemberExpression, stringLiteral} from '@babel/types';

import {TranslatePluginOptions, isLocalize} from './source_file_utils';

/**
 * This Babel plugin will replace the following code forms with a string literal containing the
 * given `locale`.
 *
 * * `$localize.locale`                     -> `"locale"`
 * * `$localize && $localize.locale`        -> `"locale"`
 * * `xxx && $localize && $localize.locale` -> `"xxx && locale"`
 * * `$localize.locale || default`          -> `"locale" || default`
 *
 * @param locale The name of the locale to inline into the code.
 * @param options Additional options including the name of the `$localize` function.
 */
export function makeLocalePlugin(
    locale: string, {localizeName = '$localize'}: TranslatePluginOptions = {}): PluginObj {
  return {
    visitor: {
      MemberExpression(expression: NodePath<MemberExpression>) {
        const obj = expression.get('object');
        if (!isLocalize(obj, localizeName)) {
          return;
        }
        const property = expression.get('property') as NodePath;
        if (!property.isIdentifier() || property.node.name !== 'locale') {
          return;
        }
        debugger;
        // Check for the `$localize.locale` being guarded by a check on the existence of
        // `$localize`.
        const parent = expression.parentPath;
        if (parent.isLogicalExpression() && parent.node.operator === '&&' &&
            parent.get('right') === expression) {
          const left = parent.get('left');
          if (isLocalize(left, localizeName)) {
            // Replace `$localize && $localize.locale` with `$localize.locale`
            parent.replaceWith(expression);
          } else if (
              left.isLogicalExpression() && left.node.operator === '&&' &&
              isLocalize(left.get('right'), localizeName)) {
            // The `$localize` is part of a preceding logical AND.
            // Replace XXX && $localize && $localize.locale` with `XXX && $localize.locale`
            left.replaceWith(left.get('left'));
          }
        }

        // Replace the `$localize.locale` with the string literal
        expression.replaceWith(stringLiteral(locale));
      }
    }
  };
}