Event: Fix handling of multiple async focus events

(cherry-picked from 24d71ac70406f522fc1b09bf7c4025251ec3aee6)

Fixes gh-4350
Closes gh-4354

1 files changed, 18 insertions, 12 deletions

diff --git a/src/event.js b/src/event.js
index b63b93b96..48d9095c9 100644
--- a/src/event.js
+++ b/src/event.js
@@ -554,9 +554,13 @@ function leverageNative( el, type, expectSync ) {
 			if ( ( event.isTrigger & 1 ) && this[ type ] ) {
 
 				// Interrupt processing of the outer synthetic .trigger()ed event
-				if ( !saved ) {
+				// Saved data should be false in such cases, but might be a leftover capture object
+				// from an async native handler (gh-4350)
+				if ( !saved.length ) {
 
 					// Store arguments for use when handling the inner native event
+					// There will always be at least one argument (an event object), so this array
+					// will not be confused with a leftover capture object.
 					saved = slice.call( arguments );
 					dataPriv.set( this, type, saved );
 
@@ -569,14 +573,14 @@ function leverageNative( el, type, expectSync ) {
 					if ( saved !== result || notAsync ) {
 						dataPriv.set( this, type, false );
 					} else {
-						result = undefined;
+						result = {};
 					}
 					if ( saved !== result ) {
 
 						// Cancel the outer synthetic event
 						event.stopImmediatePropagation();
 						event.preventDefault();
-						return result;
+						return result.value;
 					}
 
 				// If this is an inner synthetic event for an event with a bubbling surrogate
@@ -591,17 +595,19 @@ function leverageNative( el, type, expectSync ) {
 
 			// If this is a native event triggered above, everything is now in order
 			// Fire an inner synthetic event with the original arguments
-			} else if ( saved ) {
+			} else if ( saved.length ) {
 
 				// ...and capture the result
-				dataPriv.set( this, type, jQuery.event.trigger(
-
-					// Support: IE <=9 - 11+
-					// Extend with the prototype to reset the above stopImmediatePropagation()
-					jQuery.extend( saved.shift(), jQuery.Event.prototype ),
-					saved,
-					this
-				) );
+				dataPriv.set( this, type, {
+					value: jQuery.event.trigger(
+
+						// Support: IE <=9 - 11+
+						// Extend with the prototype to reset the above stopImmediatePropagation()
+						jQuery.extend( saved[ 0 ], jQuery.Event.prototype ),
+						saved.slice( 1 ),
+						this
+					)
+				} );
 
 				// Abort handling of the native event
 				event.stopImmediatePropagation();