Deferred cannot be cancelled by returning false in a callback. Exception in the callback are still propagated and execution of remaining callbacks is still possible.

src/core.js

@@ -805,10 +805,7 @@ jQuery.extend({
 	},
 	
 	// Create a simple deferred (one callbacks list)
-	_Deferred: function( cancellable ) {
+	_Deferred: function() {
-		
-		// cancellable by default
-		cancellable = cancellable !== false;
 		
 		var // callbacks list
 			callbacks = [],
@@ -852,24 +849,23 @@ jQuery.extend({
 							deferred.fire( _fired[ 0 ] , _fired[ 1 ] );
 						}
 					}
+					
 					return this;
 				},
 				
 				// resolve with given context and args
-				// (i is used internally)
+				fire: function( context , args ) {
-				fire: function( context , args , i ) {
 					if ( ! cancelled && ! fired && ! firing ) {
+						
 						firing = 1;
+						
 						try {
-							for( i = 0 ; ! cancelled && callbacks[ i ] ; i++ ) {
+							while( callbacks[ 0 ] ) {
-								cancelled = ( callbacks[ i ].apply( context , args ) === false ) && cancellable;
+								callbacks.shift().apply( context , args );
 							}
-						} catch( e ) {
+						}
-							cancelled = cancellable;
+						finally {
-							jQuery.error( e );
-						} finally {
 							fired = [ context , args ];
-							callbacks = cancelled ? [] : callbacks.slice( i + 1 );
 							firing = 0;
 						}
 					}
@@ -882,15 +878,22 @@ jQuery.extend({
 					return this;
 				},
 				
-				// cancelling further callbacks
+				// Has this deferred been resolved?
-				cancel: function() {
+				isResolved: function() {
-					if ( cancellable ) {
+					return !!( firing || fired );
-						callbacks = [];
+				},
-						cancelled = 1;
-					}
-					return this;
-				}
 				
+				// Cancel
+				cancel: function() {
+					cancelled = 1;
+					callbacks = [];
+					return this;
+				},
+				
+				// Has this deferred been cancelled?
+				isCancelled: function() {
+					return !!cancelled;
+				}
 			};
 		
 		// Add the deferred marker
@@ -901,21 +904,11 @@ jQuery.extend({
 	
 	// Full fledged deferred (two callbacks list)
 	// Typical success/error system
-	Deferred: function( func , cancellable ) {
+	Deferred: function( func ) {
 		
-		// Handle varargs
+		var errorDeferred = jQuery._Deferred(),
-		if ( arguments.length === 1 ) {
+			deferred = jQuery._Deferred(),
-			
+			successCancel = deferred.cancel;
-			if ( typeof func === "boolean" ) {
-				cancellable = func;
-				func = 0;
-			}
-		}
-		
-		var errorDeferred = jQuery._Deferred( cancellable ),
-			deferred = jQuery._Deferred( cancellable ),
-			// Keep reference of the cancel method since we'll redefine it
-			cancelThen = deferred.cancel;
 			
 		// Add errorDeferred methods and redefine cancel			
 		jQuery.extend( deferred , {
@@ -923,16 +916,16 @@ jQuery.extend({
 				fail: errorDeferred.then,
 				fireReject: errorDeferred.fire,
 				reject: errorDeferred.resolve,
-				cancel: function() {
+				isRejected: errorDeferred.isResolved
-					cancelThen();
-					errorDeferred.cancel();
-					return this;
-				}
 
 		} );
 		
+		// Remove cancel related
+		delete deferred.cancel;
+		delete deferred.isCancelled;
+		
 		// Make sure only one callback list will be used
-		deferred.then( errorDeferred.cancel ).fail( cancelThen );
+		deferred.then( errorDeferred.cancel ).fail( successCancel );
 		
 		// Call given func if any
 		if ( func ) {
@@ -979,7 +972,7 @@ jQuery.extend({
 
 // Create readyList deferred
 // also force $.fn.ready to be recognized as a defer
-readyList = jQuery._Deferred( false );
+readyList = jQuery._Deferred();
 jQuery.fn.ready._ = deferredMarker;
 
 // Populate the class2type map

test/unit/core.js

@@ -907,7 +907,7 @@ test("jQuery.parseJSON", function(){
 
 test("jQuery._Deferred()", function() {
 	
-	expect( 14 );
+	expect( 10 );
 	
 	var deferred,
 		object,
@@ -940,31 +940,19 @@ test("jQuery._Deferred()", function() {
 	test = true;
 	
 	deferred.then( function() {
-		ok( false , "Manual cancel was ignored" );
+		ok( false , "Cancel was ignored" );
 		test = false;
 	} );
 	
-	ok( test , "Test manual cancel" );
+	ok( test , "Test cancel" );
 	
-	deferred = jQuery._Deferred().then( function() {
+	deferred = jQuery._Deferred().resolve();
-		return false;
-	} );
-	
-	deferred.resolve();
-	
-	test = true;
-	
-	deferred.then( function() {
-		test = false;
-	} );
-	
-	ok( test , "Test cancel by returning false" );
 	
 	try {
-		deferred = jQuery._Deferred().resolve().then( function() {
+		deferred.then( function() {
 			throw "Error";
 		} , function() {
-			ok( false , "Test deferred cancel on exception" );
+			ok( true , "Test deferred do not cancel on exception" );
 		} );
 	} catch( e ) {
 		strictEqual( e , "Error" , "Test deferred propagates exceptions");
@@ -1003,28 +991,6 @@ test("jQuery._Deferred()", function() {
 	
 	strictEqual( test , "ABC" , "Test then callbacks order" );
 	
-	deferred = jQuery._Deferred( false ).resolve().cancel();
-	
-	deferred.then( function() {
-		ok( true , "Test non-cancellable deferred not cancelled manually");
-		return false;
-	} );
-
-	deferred.then( function() {
-		ok( true , "Test non-cancellable deferred not cancelled by returning false");
-	} );
-	
-	try {
-		deferred.then( function() {
-			throw "Error";
-		} , function() {
-			ok( true , "Test non-cancellable deferred keeps callbacks after exception" );
-		} );
-	} catch( e ) {
-		strictEqual( e , "Error" , "Test non-cancellable deferred propagates exceptions");
-		deferred.then();
-	}
-	
 	deferred = jQuery._Deferred();
 	
 	deferred.fire( jQuery , [ document ] ).then( function( doc ) {
@@ -1034,7 +1000,7 @@ test("jQuery._Deferred()", function() {
 
 test("jQuery.Deferred()", function() {
 	
-	expect( 8 );
+	expect( 4 );
 	
 	jQuery.Deferred( function( defer ) {
 		strictEqual( this , defer , "Defer passed as this & first argument" );
@@ -1054,39 +1020,6 @@ test("jQuery.Deferred()", function() {
 	}).fail( function() {
 		ok( true , "Error on reject" );
 	});
-	
-	var flag = true;
-	
-	jQuery.Deferred().resolve().cancel().then( function() {
-		ok( flag = false , "Success on resolve/cancel" );
-	}).fail( function() {
-		ok( flag = false , "Error on resolve/cancel" );
-	});
-	
-	ok( flag , "Cancel on resolve" );
-	
-	flag = true;
-	
-	jQuery.Deferred().reject().cancel().then( function() {
-		ok( flag = false , "Success on reject/cancel" );
-	}).fail( function() {
-		ok( flag = false , "Error on reject/cancel" );
-	});
-	
-	ok( flag , "Cancel on reject" );
-	
-	jQuery.Deferred( false ).resolve().then( function() {
-		return false;
-	} , function() {
-		ok( true , "Not cancelled on resolve" );
-	});
-	
-	jQuery.Deferred( false ).reject().fail( function() {
-		return false;
-	} , function() {
-		ok( true , "Not cancelled on reject" );
-	});
-	
 });
 	
 test("jQuery.isDeferred()", function() {