Fixes #4897. Added ?? as a context-insensitive placeholder for the callback...

Fixes #4897. Added ?? as a context-insensitive placeholder for the callback name of a JSONP request. Unit tests provided.

src/ajax/jsonp.js

 (function( jQuery ) {
 
 var jsc = jQuery.now(),
-	jsre = /\=(?:\?|%3F)(&|$)/i,
+	jsre = /(\=)(?:\?|%3F)(&|$)|()(?:\?\?|%3F%3F)()/i,
 	rquery_jsonp = /\?/;
 
 // Default jsonp settings
@@ -25,8 +25,8 @@ jQuery.ajax.prefilter("json jsonp", function(s, originalSettings) {
 
 		var jsonpCallback = s.jsonpCallback =
 				jQuery.isFunction( s.jsonpCallback ) ? s.jsonpCallback() : s.jsonpCallback,
-			url = s.url.replace(jsre, "=" + jsonpCallback + "$1"),
-			data = s.url === url && typeof(s.data) === "string" ? s.data.replace(jsre, "=" + jsonpCallback + "$1") : s.data;
+			url = s.url.replace(jsre, "$1" + jsonpCallback + "$2"),
+			data = s.url === url && typeof(s.data) === "string" ? s.data.replace(jsre, "$1" + jsonpCallback + "$2") : s.data;
 
 		if ( url === s.url && data === s.data ) {
 			url += (rquery_jsonp.test( url ) ? "&" : "?") + s.jsonp + "=" + jsonpCallback;

test/data/jsonp.php

 <?php
 error_reporting(0);
 $callback = $_REQUEST['callback'];
+if ( ! $callback ) {
+	$callback = explode("?",end(explode("/",$_SERVER['REQUEST_URI'])));
+	$callback = $callback[0];
+}
 $json = $_REQUEST['json'];
 if($json) {
 	echo $callback . '([ {"name": "John", "age": 21}, {"name": "Peter", "age": 25 } ])';

test/unit/ajax.js

@@ -1115,10 +1115,10 @@ test("jQuery.getScript(String, Function) - no callback", function() {
 });
 
 test("jQuery.ajax() - JSONP, Local", function() {
-	expect(10);
+	expect(14);
 
 	var count = 0;
-	function plus(){ if ( ++count == 10 ) start(); }
+	function plus(){ if ( ++count == 14 ) start(); }
 
 	stop();
 
@@ -1162,6 +1162,59 @@ test("jQuery.ajax() - JSONP, Local", function() {
 		}
 	});
 
+	jQuery.ajax({
+		url: "data/jsonp.php?callback=??",
+		dataType: "jsonp",
+		success: function(data){
+			ok( data.data, "JSON results returned (GET, url context-free callback)" );
+			plus();
+		},
+		error: function(data){
+			ok( false, "Ajax error JSON (GET, url context-free callback)" );
+			plus();
+		}
+	});
+
+	jQuery.ajax({
+		url: "data/jsonp.php",
+		dataType: "jsonp",
+		data: "callback=??",
+		success: function(data){
+			ok( data.data, "JSON results returned (GET, data context-free callback)" );
+			plus();
+		},
+		error: function(data){
+			ok( false, "Ajax error JSON (GET, data context-free callback)" );
+			plus();
+		}
+	});
+
+	jQuery.ajax({
+		url: "data/jsonp.php/??",
+		dataType: "jsonp",
+		success: function(data){
+			ok( data.data, "JSON results returned (GET, REST-like)" );
+			plus();
+		},
+		error: function(data){
+			ok( false, "Ajax error JSON (GET, REST-like)" );
+			plus();
+		}
+	});
+
+	jQuery.ajax({
+		url: "data/jsonp.php/???json=1",
+		dataType: "jsonp",
+		success: function(data){
+			strictEqual( jQuery.type(data), "array", "JSON results returned (GET, REST-like with param)" );
+			plus();
+		},
+		error: function(data){
+			ok( false, "Ajax error JSON (GET, REST-like with param)" );
+			plus();
+		}
+	});
+
 	jQuery.ajax({
 		url: "data/jsonp.php",
 		dataType: "jsonp",