"then" renamed "complete" and new "then" method defined using "complete" and "fail" internally. The API is still symetrical (complete/fail), still promotes AOP but is also now Promise/A compliant. Changed unit tests and ajax module accordingly.

src/ajax.js

@@ -496,9 +496,9 @@ jQuery.extend({
 		
 		// Attach deferreds
 		deferred.promise( jXHR );
-		jXHR.success = jXHR.then;
+		jXHR.success = jXHR.complete;
 		jXHR.error = jXHR.fail;
-		jXHR.complete = completeDeferred.then;
+		jXHR.complete = completeDeferred.complete;
 
 		// Remove hash character (#7531: and string promotion)
 		s.url = ( "" + s.url ).replace( rhash , "" );

src/core.js

@@ -258,7 +258,7 @@ jQuery.fn = jQuery.prototype = {
 		jQuery.bindReady();
 		
 		// Change ready & apply
-		return ( jQuery.fn.ready = readyList.then ).apply( this , arguments );
+		return ( jQuery.fn.ready = readyList.complete ).apply( this , arguments );
 	},
 
 	eq: function( i ) {
@@ -815,8 +815,8 @@ jQuery.extend({
 			// the deferred itself
 			deferred  = {
 				
-				// then( f1, f2, ...)
-				then: function () {
+				// complete( f1, f2, ...)
+				complete: function () {
 					
 					if ( ! cancelled ) {
 						
@@ -836,7 +836,7 @@ jQuery.extend({
 							elem = args[ i ];
 							type = jQuery.type( elem );
 							if ( type === "array" ) {
-								deferred.then.apply( deferred , elem );
+								deferred.complete.apply( deferred , elem );
 							} else if ( type === "function" ) {
 								callbacks.push( elem );
 							}
@@ -901,27 +901,31 @@ jQuery.extend({
 		// Add errorDeferred methods and redefine cancel			
 		jQuery.extend( deferred , {
 
-				fail: failDeferred.then,
-				fireReject: failDeferred.fire,
-				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 ) {
-					obj = obj || {};
-					jQuery.each( "then fail isResolved isRejected".split( " " ) , function( _ , method ) {
-						obj[ method ] = deferred[ method ];
-					});
-					obj.promise = function() {
-						return obj;
-					};
+		    then: function( completeCallbacks , failCallbacks ) {
+		    	deferred.complete( completeCallbacks ).fail( failCallbacks );
+		    	return this;
+		    },
+			fail: failDeferred.complete,
+			fireReject: failDeferred.fire,
+			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 ) {
+				obj = obj || {};
+				jQuery.each( "then complete fail isResolved isRejected".split( " " ) , function( _ , method ) {
+					obj[ method ] = deferred[ method ];
+				});
+				obj.promise = function() {
 					return obj;
-				}
+				};
+				return obj;
+			}
 
 		} );
 		
 		// Make sure only one callback list will be used
-		deferred.then( failDeferred.cancel ).fail( deferred.cancel );
+		deferred.then( failDeferred.cancel , deferred.cancel );
 		
 		// Unexpose cancel
 		delete deferred.cancel;

test/unit/core.js

@@ -917,7 +917,7 @@ test("jQuery._Deferred()", function() {
 		
 	test = false;
 		
-	deferred.then( function( value ) {
+	deferred.complete( function( value ) {
 		equals( value , "value" , "Test pre-resolve callback" );
 		test = true;
 	} );
@@ -928,7 +928,7 @@ test("jQuery._Deferred()", function() {
 
 	test = false;
 	
-	deferred.then( function( value ) {
+	deferred.complete( function( value ) {
 		equals( value , "value" , "Test post-resolve callback" );
 		test = true;
 	} );
@@ -939,7 +939,7 @@ test("jQuery._Deferred()", function() {
 	
 	test = true;
 	
-	deferred.then( function() {
+	deferred.complete( function() {
 		ok( false , "Cancel was ignored" );
 		test = false;
 	} );
@@ -949,18 +949,18 @@ test("jQuery._Deferred()", function() {
 	deferred = jQuery._Deferred().resolve();
 	
 	try {
-		deferred.then( function() {
+		deferred.complete( function() {
 			throw "Error";
 		} , function() {
 			ok( true , "Test deferred do not cancel on exception" );
 		} );
 	} catch( e ) {
 		strictEqual( e , "Error" , "Test deferred propagates exceptions");
-		deferred.then();
+		deferred.complete();
 	}
 	
 	test = "";
-	deferred = jQuery._Deferred().then( function() {
+	deferred = jQuery._Deferred().complete( function() {
 		
 		test += "A";
 		
@@ -970,13 +970,13 @@ test("jQuery._Deferred()", function() {
 		
 	} ).resolve();
 	
-	strictEqual( test , "AB" , "Test multiple then parameters" );
+	strictEqual( test , "AB" , "Test multiple complete parameters" );
 	
 	test = "";
 	
-	deferred.then( function() {
+	deferred.complete( function() {
 		
-		deferred.then( function() {
+		deferred.complete( function() {
 			
 			test += "C";
 			
@@ -989,11 +989,11 @@ test("jQuery._Deferred()", function() {
 		test += "B";
 	} );
 	
-	strictEqual( test , "ABC" , "Test then callbacks order" );
+	strictEqual( test , "ABC" , "Test complete callbacks order" );
 	
 	deferred = jQuery._Deferred();
 	
-	deferred.fire( jQuery , [ document ] ).then( function( doc ) {
+	deferred.fire( jQuery , [ document ] ).complete( function( doc ) {
 		ok( this === jQuery && arguments.length === 1 && doc === document , "Test fire context & args" );
 	});
 });
@@ -1011,13 +1011,13 @@ test("jQuery.Deferred()", function() {
 	
 	jQuery.Deferred().resolve().then( function() {
 		ok( true , "Success on resolve" );
-	}).fail( function() {
+	}, function() {
 		ok( false , "Error on resolve" );
 	});
 	
 	jQuery.Deferred().reject().then( function() {
 		ok( false , "Success on reject" );
-	}).fail( function() {
+	}, function() {
 		ok( true , "Error on reject" );
 	});
 });
@@ -1055,7 +1055,7 @@ test("jQuery.when()", function() {
 		}) ).then( function( value ) {
 			strictEqual( value , 1 , "Function executed" + ( i > 1 ? " only once" : "" ) );
 			cache = value;
-		}).fail( function() {
+		}, function() {
 			ok( false , "Fail called" );
 		});
 	}