Make sure that elements are returned in document order - and that the results are unique.

src/selector.js

@@ -111,6 +111,19 @@ var Sizzle = function(selector, context, results, seed) {
 
 	if ( extra ) {
 		Sizzle( extra, context, results, seed );
+
+		if ( sortOrder ) {
+			hasDuplicate = false;
+			results.sort(sortOrder);
+
+			if ( hasDuplicate ) {
+				for ( var i = 1; i < results.length; i++ ) {
+					if ( results[i] === results[i-1] ) {
+						results.splice(i--, 1);
+					}
+				}
+			}
+		}
 	}
 
 	return results;
@@ -648,6 +661,26 @@ try {
 	};
 }
 
+var sortOrder;
+
+if ( document.documentElement.compareDocumentPosition ) {
+	sortOrder = function( a, b ) {
+		var ret = a.compareDocumentPosition(b) & 4 ? -1 : a === b ? 0 : 1;
+		if ( ret === 0 ) {
+			hasDuplicate = true;
+		}
+		return ret;
+	};
+} else if ( document.documentElement.sourceIndex === 0 ) {
+	sortOrder = function( a, b ) {
+		var ret = a.sourceIndex - b.sourceIndex;
+		if ( ret === 0 ) {
+			hasDuplicate = true;
+		}
+		return ret;
+	};
+}
+
 // Check to see if the browser returns elements by name when
 // querying by getElementById (and provide a workaround)
 (function(){

test/unit/selector.js

 module("selector");
 
 test("element", function() {
-	expect(9);
+	expect(13);
 	reset();
 
 	ok( jQuery("*").size() >= 30, "Select all" );
@@ -18,6 +18,13 @@ test("element", function() {
 	
 	ok( jQuery("#length").length, '<input name="length"> cannot be found under IE, see #945' );
 	ok( jQuery("#lengthtest input").length, '<input name="length"> cannot be found under IE, see #945' );
+
+	// Check for unique-ness and sort order
+	isSet( jQuery("*"), jQuery("*, *"), "Check for duplicates: *, *" );
+	isSet( jQuery("p"), jQuery("p, div p"), "Check for duplicates: p, div p" );
+
+	t( "Checking sort order", "h2, h1", ["header", "banner", "userAgent"] );
+	t( "Checking sort order", "p, p a", ["firstp", "simon1", "ap", "google", "groups", "anchor1", "mark", "sndp", "en", "yahoo", "sap", "anchor2", "simon", "first"] );
 });
 
 if ( location.protocol != "file:" ) {
@@ -333,7 +340,7 @@ test("pseudo (:) selectors", function() {
 	t( "Form element :text", "#form :text", ["text1", "text2", "hidden2", "name"] );
 	t( "Form element :radio:checked", "#form :radio:checked", ["radio2"] );
 	t( "Form element :checkbox:checked", "#form :checkbox:checked", ["check1"] );
-	t( "Form element :checkbox:checked, :radio:checked", "#form :checkbox:checked, #form :radio:checked", ["check1", "radio2"] );
+	t( "Form element :radio:checked, :checkbox:checked", "#form :radio:checked, #form :checkbox:checked", ["radio2", "check1"] );
 
 	t( "Headers", ":header", ["header", "banner", "userAgent"] );
 	t( "Has Children - :has()", "p:has(a)", ["firstp","ap","en","sap"] );