fix: respect preload set to false (#1298)

Author: jeeyyy

lib/checks/mobile/css-orientation-lock.json

@@ -5,7 +5,8 @@
 		"impact": "serious",
 		"messages": {
 			"pass": "Display is operable, and orientation lock does not exist",
-			"fail": "CSS Orientation lock is applied, and makes display inoperable"
+			"fail": "CSS Orientation lock is applied, and makes display inoperable",
+			"incomplete": "CSS Orientation lock cannot be determined"
 		}
 	}
 }

lib/core/utils/preload.js

@@ -14,7 +14,7 @@ function isValidPreloadObject(preload) {
  * @return {boolean} defaults to true
  */
 axe.utils.shouldPreload = function shouldPreload(options) {
-	if (!options || !options.preload) {
+	if (!options || options.preload === undefined || options.preload === null) {
 		return true; // by default `preload` requested assets eg: ['cssom']
 	}
 	if (typeof options.preload === 'boolean') {

test/core/utils/preload.js

@@ -38,6 +38,23 @@ describe('axe.utils.preload', function() {
 			});
 	});
 
+	it('should return empty array as result', function(done) {
+		var options = {
+			preload: false
+		};
+		var actual = axe.utils.preload(options);
+		actual
+			.then(function(results) {
+				assert.isDefined(results);
+				assert.isArray(results);
+				assert.lengthOf(results, 0);
+				done();
+			})
+			.catch(function(error) {
+				done(error);
+			});
+	});
+
 	it('should return an object with property cssom and verify result is same output from preloadCssom', function(done) {
 		var options = {
 			preload: {
@@ -63,6 +80,29 @@ describe('axe.utils.preload', function() {
 
 	describe('axe.utils.shouldPreload', function() {
 		it('should return true if preload configuration is valid', function() {
+			var actual = axe.utils.shouldPreload({
+				preload: {
+					assets: ['cssom']
+				}
+			});
+			assert.isTrue(actual);
+		});
+
+		it('should return true if preload is undefined', function() {
+			var actual = axe.utils.shouldPreload({
+				preload: undefined
+			});
+			assert.isTrue(actual);
+		});
+
+		it('should return true if preload is null', function() {
+			var actual = axe.utils.shouldPreload({
+				preload: null
+			});
+			assert.isTrue(actual);
+		});
+
+		it('should return true if preload is not set', function() {
 			var actual = axe.utils.shouldPreload({});
 			assert.isTrue(actual);
 		});