Moves Deferred-related code into a separate module. Context handling has been simplified in _Deferred.resolve and jQuery.when has been refactored for clarity (and minor optimization).

src/deferred.js

@@ -0,0 +1,169 @@
+(function( jQuery ) {
+
+var // Promise methods
+	promiseMethods = "then done fail isResolved isRejected promise".split( " " ),
+	// Static reference to slice
+	sliceDeferred = [].slice;
+
+jQuery.extend({
+	// Create a simple deferred (one callbacks list)
+	_Deferred: function() {
+		var // callbacks list
+			callbacks = [],
+			// stored [ context , args ]
+			fired,
+			// to avoid firing when already doing so
+			firing,
+			// flag to know if the deferred has been cancelled
+			cancelled,
+			// the deferred itself
+			deferred  = {
+
+				// done( f1, f2, ...)
+				done: function() {
+					if ( !cancelled ) {
+						var args = arguments,
+							i,
+							length,
+							elem,
+							type,
+							_fired;
+						if ( fired ) {
+							_fired = fired;
+							fired = 0;
+						}
+						for ( i = 0, length = args.length; i < length; i++ ) {
+							elem = args[ i ];
+							type = jQuery.type( elem );
+							if ( type === "array" ) {
+								deferred.done.apply( deferred, elem );
+							} else if ( type === "function" ) {
+								callbacks.push( elem );
+							}
+						}
+						if ( _fired ) {
+							deferred.resolveWith( _fired[ 0 ], _fired[ 1 ] );
+						}
+					}
+					return this;
+				},
+
+				// resolve with given context and args
+				resolveWith: function( context, args ) {
+					if ( !cancelled && !fired && !firing ) {
+						// make sure args are available (#8421)
+						args = args || [];
+						firing = 1;
+						try {
+							while( callbacks[ 0 ] ) {
+								callbacks.shift().apply( context, args );
+							}
+						}
+						finally {
+							fired = [ context, args ];
+							firing = 0;
+						}
+					}
+					return this;
+				},
+
+				// resolve with this as context and given arguments
+				resolve: function() {
+					deferred.resolveWith( this, arguments );
+					return this;
+				},
+
+				// Has this deferred been resolved?
+				isResolved: function() {
+					return !!( firing || fired );
+				},
+
+				// Cancel
+				cancel: function() {
+					cancelled = 1;
+					callbacks = [];
+					return this;
+				}
+			};
+
+		return deferred;
+	},
+
+	// Full fledged deferred (two callbacks list)
+	Deferred: function( func ) {
+		var deferred = jQuery._Deferred(),
+			failDeferred = jQuery._Deferred(),
+			promise;
+		// Add errorDeferred methods, then and promise
+		jQuery.extend( deferred, {
+			then: function( doneCallbacks, failCallbacks ) {
+				deferred.done( doneCallbacks ).fail( failCallbacks );
+				return this;
+			},
+			fail: failDeferred.done,
+			rejectWith: failDeferred.resolveWith,
+			reject: failDeferred.resolve,
+			isRejected: failDeferred.isResolved,
+			// Get a promise for this deferred
+			// If obj is provided, the promise aspect is added to the object
+			promise: function( obj ) {
+				if ( obj == null ) {
+					if ( promise ) {
+						return promise;
+					}
+					promise = obj = {};
+				}
+				var i = promiseMethods.length;
+				while( i-- ) {
+					obj[ promiseMethods[i] ] = deferred[ promiseMethods[i] ];
+				}
+				return obj;
+			}
+		} );
+		// Make sure only one callback list will be used
+		deferred.done( failDeferred.cancel ).fail( deferred.cancel );
+		// Unexpose cancel
+		delete deferred.cancel;
+		// Call given func if any
+		if ( func ) {
+			func.call( deferred, deferred );
+		}
+		return deferred;
+	},
+
+	// Deferred helper
+	when: function( firstParam ) {
+		var args = arguments,
+			i = 0,
+			length = args.length,
+			count = length,
+			deferred = length <= 1 && firstParam && jQuery.isFunction( firstParam.promise ) ?
+				firstParam :
+				jQuery.Deferred();
+		function resolveFunc( i ) {
+			return function( value ) {
+				args[ i ] = arguments.length > 1 ? sliceDeferred.call( arguments, 0 ) : value;
+				if ( !( --count ) ) {
+					deferred.resolveWith( deferred, args );
+				}
+			};
+		}
+		if ( length > 1 ) {
+			for( ; i < length; i++ ) {
+				if ( args[ i ] && jQuery.isFunction( args[ i ].promise ) ) {
+					args[ i ].promise().then( resolveFunc(i), deferred.reject );
+				} else {
+					--count;
+				}
+			}
+			if ( !count ) {
+				deferred.resolveWith( deferred, args );
+			}
+		} else if ( deferred !== firstParam ) {
+			deferred.resolveWith( deferred, length ? [ firstParam ] : [] );
+		}
+		return deferred.promise();
+	}
+});
+
+})( jQuery );