Return correct index for no-arg index() calls. Fixes #10977. Closes gh-971

src/traversing.js

@@ -112,7 +112,7 @@ jQuery.fn.extend({
 
 		// No argument, return index in parent
 		if ( !elem ) {
-			return ( this[0] && this[0].parentNode ) ? this.prevAll().length : -1;
+			return ( this[0] && this[0].parentNode ) ? this.first().prevAll().length : -1;
 		}
 
 		// index in selector

test/unit/traversing.js

@@ -651,3 +651,12 @@ test("eq('-1') #10616", function() {
 	equal( $divs.eq( "-1" ).length, 1, "The string '-1' returns a selection that has length 1" );
 	deepEqual( $divs.eq( "-1" ), $divs.eq( -1 ), "String and number -1 match" );
 });
+
+test("index(no arg) #10977", function() {
+	expect(1);
+	
+	var $list = jQuery("<ul id='indextest'><li>THIS ONE</li><li class='one'>a</li><li class='two'>b</li><li class='three'>c</li></ul>");
+	jQuery("#qunit-fixture").append( $list );
+	strictEqual ( jQuery( "#indextest li:not(.one,.two)" ).index() , 0, "No Argument Index Check" );
+	$list.remove();
+});