feat: don't throw when re-registering a plugin unless it's a player m…

…ethod (#4140)

src/js/plugin.js

@@ -5,6 +5,7 @@ import evented from './mixins/evented';
 import stateful from './mixins/stateful';
 import * as Events from './utils/events';
 import * as Fn from './utils/fn';
+import log from './utils/log';
 import Player from './player';
 
 /**
@@ -305,8 +306,10 @@ class Plugin {
       throw new Error(`Illegal plugin name, "${name}", must be a string, was ${typeof name}.`);
     }
 
-    if (pluginExists(name) || Player.prototype.hasOwnProperty(name)) {
-      throw new Error(`Illegal plugin name, "${name}", already exists.`);
+    if (pluginExists(name)) {
+      log.warn(`A plugin named "${name}" already exists. You may want to avoid re-registering plugins!`);
+    } else if (Player.prototype.hasOwnProperty(name)) {
+      throw new Error(`Illegal plugin name, "${name}", cannot share a name with an existing player method!`);
     }
 
     if (typeof plugin !== 'function') {

test/unit/plugin-static.test.js

@@ -1,4 +1,6 @@
 /* eslint-env qunit */
+import sinon from 'sinon';
+import log from '../../src/js/utils/log';
 import Player from '../../src/js/player';
 import Plugin from '../../src/js/plugin';
 
@@ -53,12 +55,6 @@ QUnit.test('registerPlugin() illegal arguments', function(assert) {
     'plugins must have a name'
   );
 
-  assert.throws(
-    () => Plugin.registerPlugin('play'),
-    new Error('Illegal plugin name, "play", already exists.'),
-    'plugins cannot share a name with an existing player method'
-  );
-
   assert.throws(
     () => Plugin.registerPlugin('foo'),
     new Error('Illegal plugin for "foo", must be a function, was undefined.'),
@@ -70,6 +66,18 @@ QUnit.test('registerPlugin() illegal arguments', function(assert) {
     new Error('Illegal plugin for "foo", must be a function, was object.'),
     'plugins must be functions'
   );
+
+  assert.throws(
+    () => Plugin.registerPlugin('play', function() {}),
+    new Error('Illegal plugin name, "play", cannot share a name with an existing player method!'),
+    'plugins must be functions'
+  );
+
+  sinon.spy(log, 'warn');
+  Plugin.registerPlugin('foo', function() {});
+  Plugin.registerPlugin('foo', function() {});
+  assert.strictEqual(log.warn.callCount, 1, 'warn on re-registering a plugin');
+  log.warn.restore();
 });
 
 QUnit.test('getPlugin()', function(assert) {