Deferred: Make jQuery.when synchronous when possible

Closes gh-3102
Fixes gh-3100
Closes gh-3105

1 files changed, 7 insertions, 2 deletions

diff --git a/src/deferred.js b/src/deferred.js
index 6e4d43b31..73b2f9ef2 100644
--- a/src/deferred.js
+++ b/src/deferred.js
@@ -366,16 +366,21 @@ jQuery.extend( {
 
 		// Single- and empty arguments are adopted like Promise.resolve
 		if ( remaining <= 1 ) {
-			adoptValue( singleValue, master.resolve, master.reject );
+			adoptValue( singleValue, master.done( updateFunc( i ) ).resolve, master.reject );
 
 			// Use .then() to unwrap secondary thenables (cf. gh-3000)
-			return master.then();
+			if ( master.state() === "pending" ||
+				jQuery.isFunction( resolveValues[ i ] && resolveValues[ i ].then ) ) {
+
+				return master.then();
+			}
 		}
 
 		// Multiple arguments are aggregated like Promise.all array elements
 		while ( i-- ) {
 			adoptValue( resolveValues[ i ], updateFunc( i ), master.reject );
 		}
+
 		return master.promise();
 	}
 } );