Event: Patch jQuery.event.special's prototype

Allow to use common `Object.prototype` properties on `jQuery.event.special` but
warn as well.

Closes gh-572
Fixes gh-542

Author: mgol

src/jquery/event.js

@@ -5,6 +5,7 @@ import {
 	migrateWarnProp
 } from "../main.js";
 import "../disablePatches.js";
+import { patchProto } from "../utils.js";
 
 var oldLoad = jQuery.fn.load,
 	oldEventAdd = jQuery.event.add,
@@ -136,3 +137,11 @@ migratePatchAndWarnFunc( jQuery.fn, "undelegate", function( selector, types, fn
 migratePatchAndWarnFunc( jQuery.fn, "hover", function( fnOver, fnOut ) {
 	return this.on( "mouseenter", fnOver ).on( "mouseleave", fnOut || fnOver );
 }, "pre-on-methods", "jQuery.fn.hover() is deprecated" );
+
+// We can apply the patch unconditionally here as in the `3.x` line the API
+// inherits from `Object.prototype` even without a patch and `migrateWarn`
+// inside `patchProto` will already silence warnings if the patch gets disabled.
+patchProto( jQuery.event.special, {
+	warningId: "event-special-null-proto",
+	apiName: "jQuery.event.special"
+} );

test/unit/jquery/event.js

@@ -190,3 +190,27 @@ TestManager.runIframeTest( "Load within a ready handler", "event-lateload.html",
 			JSON.stringify( jQuery.migrateWarnings ) );
 		assert.ok( /load/.test( jQuery.migrateWarnings[ 0 ] ), "message ok" );
 	} );
+
+QUnit.test( "jQuery.event.special: properties from Object.prototype", function( assert ) {
+	assert.expect( 4 );
+
+	try {
+		expectNoWarning( assert, "Regular properties", function() {
+			jQuery.event.special.fakeevent = {};
+
+			// eslint-disable-next-line no-unused-expressions
+			jQuery.event.special.fakeevent;
+		} );
+
+		(
+			Object.setPrototypeOf ? expectWarning : expectNoWarning
+		)( assert, "Properties from Object.prototype", 2, function() {
+			assert.ok( jQuery.event.special.hasOwnProperty( "fakeevent" ),
+				"hasOwnProperty works (property present)" );
+			assert.ok( !jQuery.event.special.hasOwnProperty( "fakeevent2" ),
+				"hasOwnProperty works (property missing)" );
+		} );
+	} finally {
+		delete jQuery.event.special.fakeevent;
+	}
+} );