Replaces "text in-between" technique with a full-fledged one-level transitive search for converters (unit tests added). Also cleans up auto dataType determination and adds converter checks in order to guess the best dataType possible.

src/ajax.js

@@ -372,8 +372,9 @@ jQuery.extend({
 				clearTimeout(timeoutTimer);
 			}
 
-			var // Reference dataTypes and responseFields
+			var // Reference dataTypes, converters and responseFields
 				dataTypes = s.dataTypes,
+				converters = s.converters,
 				responseFields = s.responseFields,
 				responseField,
 
@@ -400,44 +401,64 @@ jQuery.extend({
 					transportDataType = dataTypes[0],
 					ct,
 					type,
-					finalDataType;
+					finalDataType,
+					firstDataType;
 
 				// Auto (xml, json, script or text determined given headers)
-				if ( transportDataType === "*" && ( ct = jXHR.getResponseHeader( "content-type" ) ) ) {
+				if ( transportDataType === "*" ) {
 
+					// Remove all auto types
+					while( dataTypes[0] === "*" ) {
+						dataTypes.shift();
+					}
+					transportDataTypes = dataTypes[0];
+
+					// Get content type
+					ct = jXHR.getResponseHeader( "content-type" );
+
+					// Check if it's a known type
 					for ( type in contents ) {
 						if ( contents[ type ] && contents[ type ].test( ct ) ) {
-							transportDataType = dataTypes[0] = type;
+							dataTypes.unshift( ( transportDataType = type ) );
 							break;
 						}
 					}
-
-					type = undefined;
 				}
 
-				// Get final dataType
+				// Check to see if we have a response for the expected dataType
-				for( type in responses ) {
+				if ( transportDataType in responses ) {
-					if ( ! finalDataType && type === transportDataType ) {
+					finalDataType = transportDataType;
+				} else {
+					// Try convertible dataTypes
+					for ( type in responses ) {
+						if ( ! firstDataType ) {
+							firstDataType = type;
+						}
+						if ( ! transportDataType || converters[ type + " " + transportDataType ] ) {
 							finalDataType = type;
+							break;
 						}
-					responseField = responseFields[ type ];
-					if ( responseField && ! ( responseField in jXHR ) ) {
-						jXHR[ responseField ] = responses[ type ];
 					}
+					// Or just use first one
+					finalDataType = finalDataType || firstDataType;
 				}
 
-				// If no response with the expected dataType was provided
+				// If we found a dataType
-				// Take the last response as a default if it exists
+				// We get the corresponding response
-				if ( ! finalDataType && type ) {
+				// and add the dataType to the list if needed
-					finalDataType = type;
+				if ( finalDataType ) {
-					if ( transportDataType === "*" ) {
+					response = responses[ finalDataType ];
-						dataTypes.shift();
+					if ( finalDataType !== transportDataType ) {
-					}
 						dataTypes.unshift( finalDataType );
 					}
+				}
 
-				// Get final response
+				// Fill responseXXX fields
-				response = responses[ finalDataType ];
+				for( type in responseFields ) {
+					if ( type in responses ) {
+						jXHR[ responseFields[ type ] ] = responses[ type ];
+					}
+				}
 			}
 
 			// If successful, handle type chaining
@@ -473,6 +494,7 @@ jQuery.extend({
 					try {
 
 						var i,
+							tmp,
 							// Current dataType
 							current,
 							// Previous dataType
@@ -483,9 +505,7 @@ jQuery.extend({
 							conv,
 							// Conversion functions (when text is used in-between)
 							conv1,
-							conv2,
+							conv2;
-							// Local references to converters
-							converters = s.converters;
 
 						// For each dataType in the chain
 						for( i = 0 ; i < dataTypes.length ; i++ ) {
@@ -505,27 +525,32 @@ jQuery.extend({
 								// Get the dataType to convert from
 								prev = dataTypes[ i - 1 ];
 
-								// If no catch-all and dataTypes are actually different
+								// If no auto and dataTypes are actually different
 								if ( prev !== "*" && current !== "*" && prev !== current ) {
 
 									// Get the converter
 									conversion = prev + " " + current;
 									conv = converters[ conversion ] || converters[ "* " + current ];
 
-									conv1 = conv2 = 0;
+									// If there is no direct converter, search transitively
+									if ( ! conv ) {
+										conv1 = conv2 = undefined;
 
-									// If there is no direct converter and none of the dataTypes is text
+										for( conv1 in converters ) {
-									if ( ! conv && prev !== "text" && current !== "text" ) {
+											tmp = conv1.split( " " );
-										// Try with text in-between
+											if ( tmp[ 0 ] === prev || tmp[ 0 ] === "*" ) {
-										conv1 = converters[ prev + " text" ] || converters[ "* text" ];
+												conv2 = converters[ tmp[ 1 ] + " " + current ];
-										conv2 = converters[ "text " + current ];
+												if ( conv2 ) {
-										// Revert back to a single converter
+													conv1 = converters[ conv1 ];
-										// if one of the converter is an equivalence
 													if ( conv1 === true ) {
 														conv = conv2;
 													} else if ( conv2 === true ) {
 														conv = conv1;
 													}
+													break;
+												}
+											}
+										}
 									}
 									// If we found no converter, dispatch an error
 									if ( ! ( conv || conv1 && conv2 ) ) {

test/unit/ajax.js

@@ -2006,6 +2006,49 @@ test( "jQuery.ajax - statusCode" , function() {
 	});
 });
 
+test("jQuery.ajax - transitive conversions", function() {
+
+	expect( 8 );
+
+	stop();
+
+	jQuery.when(
+
+		jQuery.ajax( url("data/json.php") , {
+			converters: {
+				"json myjson": function( data ) {
+					ok( true , "converter called" );
+					return data;
+				}
+			},
+			dataType: "myjson",
+			success: function() {
+				ok( true , "Transitive conversion worked" );
+				strictEqual( this.dataTypes[0] , "text" , "response was retrieved as text" );
+				strictEqual( this.dataTypes[1] , "myjson" , "request expected myjson dataType" );
+			}
+		}),
+
+		jQuery.ajax( url("data/json.php") , {
+			converters: {
+				"json myjson": function( data ) {
+					ok( true , "converter called (*)" );
+					return data;
+				}
+			},
+			contents: false, /* headers are wrong so we ignore them */
+			dataType: "* myjson",
+			success: function() {
+				ok( true , "Transitive conversion worked (*)" );
+				strictEqual( this.dataTypes[0] , "text" , "response was retrieved as text (*)" );
+				strictEqual( this.dataTypes[1] , "myjson" , "request expected myjson dataType (*)" );
+			}
+		})
+
+	).then( start , start );
+
+});
+
 test("jQuery.ajax - active counter", function() {
     ok( jQuery.active == 0, "ajax active counter should be zero: " + jQuery.active );
 });