[ASDisplayNode] Allow explicit setting of accessibilityElements (Text…

…ureGroup#1807)

* [ASDisplayNode] Allow explicit setting of accessibilityElements

Since `NSObject` conforms to the informal accessibility protocol, `ASDisplayNode` has an inherited property for `accessibilityElements`. However, setting this property has no effect since `ASDisplayNode` overrides the `accessibilityElements` getter. Added a small change to the getter to check if the `accessibilityElements` property on `ASDisplayNode` has been explicitly set, and if so return that.

I also added a comment around  `_ASDisplayView`’s `setAccessibilityElements:` method to clear up some (of my own) confusion.

* comment tweak

* Fix flakey test

Source/Details/_ASDisplayViewAccessiblity.mm

@@ -259,6 +259,10 @@ @implementation _ASDisplayView (UIAccessibilityContainer)
 - (void)setAccessibilityElements:(NSArray *)accessibilityElements
 {
   ASDisplayNodeAssertMainThread();
+  // While it looks very strange to ignore the accessibilyElements param and set _accessibilityElements to nil, it is actually on purpose.
+  // _ASDisplayView's accessibilityElements method will always defer to the node for accessibilityElements when _accessibilityElements is
+  // nil. Calling setAccessibilityElements on _ASDisplayView is basically clearing the cache and forcing _ASDisplayView to ask the node
+  // for its accessibilityElements the next time they are requested.
   _accessibilityElements = nil;
 }
 
@@ -283,6 +287,14 @@ @implementation ASDisplayNode (AccessibilityInternal)
 
 - (NSArray *)accessibilityElements
 {
+  // NSObject implements the informal accessibility protocol. This means that all ASDisplayNodes already have an accessibilityElements
+  // property. If an ASDisplayNode subclass has explicitly set the property, let's use that instead of traversing the node tree to try
+  // to create the elements automatically
+  NSArray *elements = [super accessibilityElements];
+  if (elements.count) {
+    return elements;
+  }
+
   if (!self.isNodeLoaded) {
     ASDisplayNodeFailAssert(@"Cannot access accessibilityElements since node is not loaded");
     return @[];

Tests/ASDisplayViewAccessibilityTests.mm

@@ -12,6 +12,8 @@
 
 #import <XCTest/XCTest.h>
 
+#import <AsyncDisplayKit/_ASDisplayView.h>
+#import <AsyncDisplayKit/ASButtonNode.h>
 #import <AsyncDisplayKit/ASDisplayNode.h>
 #import <AsyncDisplayKit/ASDisplayNode+Beta.h>
 #import <AsyncDisplayKit/ASTextNode.h>
@@ -193,4 +195,60 @@ - (void)testActionForwarding {
   OCMVerifyAll(mockNode);
 }
 
+#pragma mark -
+#pragma mark AccessibilityElements
+
+// dummy action for a button
+- (void)fakeSelector:(id)sender { }
+
+- (void)testThatAccessibilityElementsWorks {
+  ASDisplayNode *containerNode = [[ASDisplayNode alloc] init];
+  containerNode.frame = CGRectMake(0, 0, 100, 200);
+
+  ASTextNode *label = [[ASTextNode alloc] init];
+  label.attributedText = [[NSAttributedString alloc] initWithString:@"test label"];
+  label.frame = CGRectMake(0, 0, 100, 20);
+
+  ASButtonNode *button = [[ASButtonNode alloc] init];
+  [button setTitle:@"tap me" withFont:[UIFont systemFontOfSize:17] withColor:nil forState:UIControlStateNormal];
+  [button addTarget:self action:@selector(fakeSelector:) forControlEvents:ASControlNodeEventTouchUpInside];
+  button.frame = CGRectMake(0, 25, 100, 20);
+
+  [containerNode addSubnode:label];
+  [containerNode addSubnode:button];
+
+  // force load
+  __unused UIView *view = containerNode.view;
+
+  NSArray *elements = [containerNode accessibilityElements];
+  XCTAssertTrue(elements.count == 2);
+  XCTAssertEqual([elements.firstObject asyncdisplaykit_node], label);
+  XCTAssertEqual([elements.lastObject asyncdisplaykit_node], button);
+}
+
+- (void)testThatAccessibilityElementsOverrideWorks {
+  ASDisplayNode *containerNode = [[ASDisplayNode alloc] init];
+  containerNode.frame = CGRectMake(0, 0, 100, 200);
+
+  ASTextNode *label = [[ASTextNode alloc] init];
+  label.attributedText = [[NSAttributedString alloc] initWithString:@"test label"];
+  label.frame = CGRectMake(0, 0, 100, 20);
+
+  ASButtonNode *button = [[ASButtonNode alloc] init];
+  [button setTitle:@"tap me" withFont:[UIFont systemFontOfSize:17] withColor:nil forState:UIControlStateNormal];
+  [button addTarget:self action:@selector(fakeSelector:) forControlEvents:ASControlNodeEventTouchUpInside];
+  button.frame = CGRectMake(0, 25, 100, 20);
+
+  [containerNode addSubnode:label];
+  [containerNode addSubnode:button];
+  containerNode.accessibilityElements = @[ label ];
+
+  // force load
+  __unused UIView *view = containerNode.view;
+
+  NSArray *elements = [containerNode accessibilityElements];
+  XCTAssertTrue(elements.count == 1);
+  XCTAssertEqual(elements.firstObject, label);
+}
+
 @end

Tests/ASViewControllerTests.mm

@@ -77,8 +77,9 @@ - (void)testThatViewControllerFrameIsRightAfterCustomTransitionWithNonextendedEd
   nav.delegate = navDelegate;
   window.rootViewController = nav;
   [window makeKeyAndVisible];
-  [[NSRunLoop mainRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate date]];
+  [[NSRunLoop mainRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:2]];
   [nav pushViewController:vc animated:YES];
+  [[NSRunLoop mainRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:2]];
 
   [self waitForExpectationsWithTimeout:2 handler:nil];