Make sure to call jsonp always as script tag. Fix for #5955 with unit test.

Fixing this bug is simple and for me it won't break any unit tests.
The unit test I've added is a bit strange, but worked for me across Firefox 3.6, Chrome and IE6.

Author: irae

src/ajax.js

@@ -289,7 +289,7 @@ jQuery.extend({
 
 		// If we're requesting a remote document
 		// and trying to load JSON or Script with a GET
-		if ( s.dataType === "script" && type === "GET" && remote ) {
+		if ( s.dataType === "script" && type === "GET" && (remote || jsonp) ) {
 			var head = document.getElementsByTagName("head")[0] || document.documentElement;
 			var script = document.createElement("script");
 			script.src = s.url;

test/data/jsonp.php

@@ -2,7 +2,21 @@
 error_reporting(0);
 $callback = $_REQUEST['callback'];
 $json = $_REQUEST['json'];
-if($json) {
+$verifyScriptTag = $_REQUEST['verifyScriptTag'];
+if($verifyScriptTag) {
+	?>
+	window.isScriptTag = false;
+	(function(){
+		var i,script,scripts = document.getElementsByTagName('script');
+		for ( i=0 ; i < scripts.length ; i++ ) { script = scripts[i];
+		    if( (''+script.src).indexOf('verifyScriptTag') != -1 ) {
+		        window.isScriptTag = true;
+		    }
+		}
+	})();
+	<?php	
+	echo $callback . '({ "whatever": "data" })';
+} else if($json) {
 	echo $callback . '([ {"name": "John", "age": 21}, {"name": "Peter", "age": 25 } ])';
 } else {
 	echo $callback . '({ "data": {"lang": "en", "length": 25} })';

test/unit/ajax.js

@@ -770,8 +770,8 @@ test("JSONP - Custom JSONP Callback", function() {
 	});
 });
 
-test("jQuery.ajax() - JSONP, Remote", function() {
-	expect(4);
+test("jQuery.ajax() - JSONP, Remote or Local", function() {
+	expect(5);
 
 	var count = 0;
 	function plus(){ if ( ++count == 4 ) start(); }
@@ -833,6 +833,20 @@ test("jQuery.ajax() - JSONP, Remote", function() {
 			plus();
 		}
 	});
+
+	jQuery.ajax({
+		url: base + "data/jsonp.php",
+		dataType: "jsonp",
+		data: {"verifyScriptTag":true},
+		success: function(data){
+			ok( window.isScriptTag, "JSONP is script tag" );
+			// garbage collect
+			try {
+				delete window.isScriptTag;
+			} catch(e) {}
+			plus();
+		}
+	});
 });
 
 test("jQuery.ajax() - script, Remote", function() {