Event: Patch jQuery.event.special's prototype

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

Fixes gh-542

Author: mgol

src/jquery/event.js

@@ -1,9 +1,11 @@
 import {
 	migrateWarn,
 	migratePatchAndInfoFunc,
-	migratePatchFunc
+	migratePatchFunc,
+	migratePatchProp
 } from "../main.js";
 import "../disablePatches.js";
+import { patchProto } from "../utils.js";
 
 var oldEventAdd = jQuery.event.add;
 
@@ -41,3 +43,10 @@ migratePatchAndInfoFunc( jQuery.fn, "undelegate", jQuery.fn.undelegate,
 
 migratePatchAndInfoFunc( jQuery.fn, "hover", jQuery.fn.hover,
 	"hover", "jQuery.fn.hover() is deprecated" );
+
+migratePatchProp( jQuery.event, "special",
+	patchProto( jQuery.extend( Object.create( null ), jQuery.event.special ), {
+		warningId: "event-special-null-proto",
+		apiName: "jQuery.event.special"
+	} ),
+	"event-special-null-proto" );

test/unit/jquery/event.js

@@ -84,3 +84,25 @@ TestManager.runIframeTest( "Load within a ready handler", "event-lateload.html",
 			JSON.stringify( jQuery.migrateMessages ) );
 		assert.ok( /load/.test( jQuery.migrateMessages[ 0 ] ), "message ok" );
 	} );
+
+QUnit.test( "jQuery.event.special: properties from Object.prototype", function( assert ) {
+	assert.expect( 4 );
+
+	try {
+		expectNoMessage( assert, "Regular properties", function() {
+			jQuery.event.special.fakeevent = {};
+
+			// eslint-disable-next-line no-unused-expressions
+			jQuery.event.special.fakeevent;
+		} );
+
+		expectMessage( 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;
+	}
+} );