Make default comparison assert that undefined > null > any other value

Fixes dojo#131 by making the default comparison function created in
SimpleQuery#_createSortQuerier treat undefined as greater than any
value, and null greater than any value besides undefined.
This conveniently places all null and undefined values at
the end of a sorted list.

src/SimpleQuery.js

@@ -162,10 +162,8 @@ define([
 						return object[properties];
 					});
 			};
-		}
+		},
 
-		/* jshint ignore:start */
-		,
 		_createSortQuerier: function (sorted) {
 			var queryAccessors = this.queryAccessors;
 			return function (data) {
@@ -184,10 +182,16 @@ define([
 
 							aValue != null && (aValue = aValue.valueOf());
 							bValue != null && (bValue = bValue.valueOf());
-
-							comparison = aValue === bValue
-								? 0
-								: (!!descending === (aValue === null || aValue > bValue && bValue !== null) ? -1 : 1);
+							if (aValue === bValue) {
+								comparison = 0;
+							}
+							else {
+								// Prioritize undefined > null > defined
+								var isALessThanB = typeof bValue === 'undefined' ||
+									bValue === null && typeof aValue !== 'undefined' ||
+									aValue != null && aValue < bValue;
+								comparison = Boolean(descending) === isALessThanB ? 1 : -1;
+							}
 						}
 
 						if (comparison !== 0) {
@@ -199,6 +203,5 @@ define([
 				return data;
 			};
 		}
-		/* jshint ignore:end */
 	});
 });

tests/unit/SimpleQuery.js

@@ -72,6 +72,65 @@ define([
 			]);
 		},
 
+		'sort null and undefined with strings': function () {
+			var sort = simpleQuery._createSortQuerier([ { property: 'name' } ]);
+			var sortDescending = simpleQuery._createSortQuerier([ { descending: true, property: 'name' } ]);
+			var data = testData.slice();
+			data.splice(2 , 0, { id: 6, odd: false });
+			data.splice(2, 0, { id: 7, name: null, odd: true });
+
+			assert.deepEqual(sort(data), [
+				{ id: 5, name: 'five', odd: true },
+				{ id: 4, name: 'four', odd: false },
+				{ id: 1, name: 'one', odd: true },
+				{ id: 3, name: 'three', odd: true },
+				{ id: 2, name: 'two', odd: false },
+				{ id: 7, name: null, odd: true },
+				{ id: 6, odd: false }
+			]);
+
+			assert.deepEqual(sortDescending(data), [
+				{ id: 6, odd: false },
+				{ id: 7, name: null, odd: true },
+				{ id: 2, name: 'two', odd: false },
+				{ id: 3, name: 'three', odd: true },
+				{ id: 1, name: 'one', odd: true },
+				{ id: 4, name: 'four', odd: false },
+				{ id: 5, name: 'five', odd: true }
+			]);
+		},
+
+		'sort null and undefined with numbers': function () {
+			var sort = simpleQuery._createSortQuerier([ { property: 'id' } ]);
+			var sortDescending = simpleQuery._createSortQuerier([ { descending: true, property: 'id' } ]);
+			var data = testData.slice();
+			data.splice(2 , 0, {});
+			data.splice(2, 0, { id: null});
+			data.splice(2, 0, { id: -1});
+
+			assert.deepEqual(sort(data), [
+				{ id: -1 },
+				{ id: 1, name: 'one', odd: true },
+				{ id: 2, name: 'two', odd: false },
+				{ id: 3, name: 'three', odd: true },
+				{ id: 4, name: 'four', odd: false },
+				{ id: 5, name: 'five', odd: true },
+				{ id: null },
+				{}
+			]);
+
+			assert.deepEqual(sortDescending(data), [
+				{},
+				{ id: null },
+				{ id: 5, name: 'five', odd: true },
+				{ id: 4, name: 'four', odd: false },
+				{ id: 3, name: 'three', odd: true },
+				{ id: 2, name: 'two', odd: false },
+				{ id: 1, name: 'one', odd: true },
+				{ id: -1 }
+			]);
+		},
+
 		'nested queries': function () {
 			var f = new Filter.default();
 			var isEven = f.eq('odd', false);