Add Player#tech.

src/js/player.js

@@ -612,6 +612,30 @@ class Player extends Component {
     this.tech_ = false;
   }
 
+  /**
+   * Return a reference to the current tech.
+   * It will only return a reference to the tech if given an object with the
+   * `IWillNotUseThisInPlugins` property on it. This is try and prevent misuse
+   * of techs by plugins.
+   *
+   * @param {Object}
+   * @return {Object} The Tech
+   * @method tech
+   */
+  tech(safety) {
+    if (safety && safety.IWillNotUseThisInPlugins) {
+      return this.tech_;
+    }
+    let errorText = `
+      Please make sure that you are not using this inside of a plugin.
+      To disable this alert and error, please pass in an object with
+      \`IWillNotUseThisInPlugins\` to the \`tech\` method. See
+      https://github.com/videojs/video.js/issues/2617 for more info.
+    `;
+    window.alert(errorText);
+    throw new Error(errorText);
+  }
+
   /**
    * Set up click and touch listeners for the playback element
    *

test/unit/player.test.js

@@ -7,6 +7,7 @@ import MediaError from '../../src/js/media-error.js';
 import Html5 from '../../src/js/tech/html5.js';
 import TestHelpers from './test-helpers.js';
 import document from 'global/document';
+import window from 'global/window';
 import Tech from '../../src/js/tech/tech.js';
 import TechFaker from './tech/tech-faker.js';
 
@@ -861,3 +862,25 @@ test('you can clear error in the error event', function() {
 
   log.error.restore();
 });
+
+test('Player#tech will return tech given the appropriate input', function() {
+  let tech_ = {};
+  let returnedTech = Player.prototype.tech.call({tech_}, {IWillNotUseThisInPlugins: true});
+
+  equal(returnedTech, tech_, 'We got back the tech we wanted');
+});
+
+test('Player#tech alerts and throws without the appropriate input', function() {
+  let alertCalled;
+  let oldAlert = window.alert;
+  window.alert = () => alertCalled = true;
+
+  let tech_ = {};
+  throws(function() {
+    Player.prototype.tech.call({tech_});
+  }, new RegExp('https://github.com/videojs/video.js/issues/2617'),
+  'we threw an error');
+
+  ok(alertCalled, 'we called an alert');
+  window.alert = oldAlert;
+});