Closure compiler warns about undefined property from extern

Question

The closure compiler a warning about a property that isn't defined on an extern when as far as I can tell the property is defined on that extern.

I would like to get the closure compiler to compile this cleanly without issuing this warning.

I am using the following options for the compiler:

• angular_pass
• compilation_level=ADVANCED_OPTIMIZATIONS
• create_source_map
• language_in=ECMASCRIPT5_STRICT
• manage_closure_dependencies
• warning_level=VERBOSE

The warning that is produced is:

trFilter.js:19: WARNING - Property instant never defined on pascalprecht.translate.$translate
            target = $translate.instant(texts.toString());
                     ^

The file that produces the warning has the following contents:

var myApp = {};

/*
 * The trFilter generates translated strings.
 */
(function () {
  'use strict';

  /**
   * @param {pascalprecht.translate.$translate} $translate
   * @returns {function((Array.<string>|string)): string}
   */
  var trFilter = function ($translate) {
    return function(texts) {
      var target;
      target = $translate.instant(texts.toString());
      return target;
    };
  };

  myApp.trFilter = ['$translate', trFilter];
})();

angular.module('myApp')
    .filter('tr', myApp.trFilter);

My extern for angular-translate contains the following:

/**
 * @fileoverview Externs for Angular Translate.
 * @externs
 */

/**
 * Base namespace
 * @type {Object}
 * @const
 */
var pascalprecht = {};
goog.provide('pascalprecht');

/**
 * angular-translate namespace
 * @type {Object}
 * @const
 */
pascalprecht.translate = {};
goog.provide('pascalprecht.translate');

/**
 * The $translate service
 * @constructor
 */
pascalprecht.translate.$translate;
goog.provide('pascalprecht.translate.$translate');

/**
 * Returns a translation instantly from the internal state of loaded translation. All rules
 * regarding the current language, the preferred language of even fallback languages will be
 * used except any promise handling. If a language was not found, an asynchronous loading
 * will be invoked in the background.
 *
 * @param {string} translationId Translation ID
 * @param {Object=} interpolateParams Params
 * @param {string=} interpolationId
 *
 * @return {string} translation
 */
pascalprecht.translate.$translate.instant = function (translationId, interpolateParams, interpolationId) {};
goog.exportProperty(pascalprecht.translate.$translate, 'instant',  pascalprecht.translate.$translate.instant);

I don't think the goog.provide() and goog.exportProperty() calls are required in the extern file. I have tested with and without them in the file, but they don't seem to make any difference.

I am running closure using the grunt-closure-compiler grunt helper.

Changing to warning_level=QUIET does eliminate the warning, but it also eliminates warnings about things that would be an issue. For example, if I change the call to this:

target = $translate.instatn(texts.toString(());

I would like to get a warning, because there is no instatn() function on the $translate object.

What do I need to change to get the closure compiler to find the correct extern function in this case?

Answer 1

I try this:

/**
 * The $translate service
 * @type {Object}
 * @constructor
 */
pascalprecht.translate.$translate;
goog.provide('pascalprecht.translate.$translate');

(put the @type {Object}). And the

"WARNING - Property instant never defined on pascalprecht.translate.$translate"

not show more.