Preload accessibility framework if not already loaded

Summary:
It looks like there are some edge cases when app did not load private accessibility framework (probably if it never set any accessibility values?)

This diff makes calls to accessibility hierarchy safer and ensures to preload framework if available

Reviewed By: lblasa

Differential Revision: D49501064

fbshipit-source-id: b46216b58bf6c9c63f900e199fea035e3262afb2

iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Serializers/UIDInitEvent+Foundation.m

@@ -8,6 +8,7 @@
 #if FB_SONARKIT_ENABLED
 
 #import "NSArray+Foundation.h"
+#import "UIDAllyTraversal.h"
 #import "UIDInitEvent+Foundation.h"
 #import "UIDTraversalMode.h"
 
@@ -20,12 +21,15 @@ FB_LINKABLE(UIDInitEvent_Foundation)
     @"frameworkEventMetadata" : self.frameworkEventMetadata
         ? [self.frameworkEventMetadata toFoundation]
         : @[],
-    @"supportedTraversalModes" : @[
+    @"supportedTraversalModes" : UIDAllyTraversal.isSupported ? @[
       NSStringFromUIDTraversalMode(UIDTraversalModeViewHierarchy),
       NSStringFromUIDTraversalMode(UIDTraversalModeAccessibilityHierarchy),
+    ] : @[
+      NSStringFromUIDTraversalMode(UIDTraversalModeViewHierarchy),
     ],
-    @"currentTraversalMode" :
-        NSStringFromUIDTraversalMode(self.currentTraversalMode),
+    @"currentTraversalMode" : NSStringFromUIDTraversalMode(
+        UIDAllyTraversal.isSupported ? self.currentTraversalMode
+                                     : UIDTraversalModeViewHierarchy),
   };
 }
 

iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.h

@@ -17,6 +17,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface UIDAllyTraversal : NSObject
 
+@property(nonatomic, class, readonly, getter=isSupported) BOOL supported;
+
 - (instancetype)initWithDescriptorRegister:
     (UIDDescriptorRegister*)descriptorRegister;
 

iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.m

@@ -27,6 +27,13 @@
   UIDDescriptorRegister* _descriptorRegister;
 }
 
++ (BOOL)isSupported {
+  return _loadAccessibilityFramework() &&
+      [UIApplication.sharedApplication
+             respondsToSelector:@selector
+             (_accessibilityLeafDescendantsWithOptions:)];
+}
+
 - (instancetype)initWithDescriptorRegister:
     (UIDDescriptorRegister*)descriptorRegister {
   self = [super init];
@@ -41,10 +48,18 @@
     return @[];
   }
 
+  if (!_loadAccessibilityFramework()) {
+    return @[];
+  }
+
   // create voice over representation of the app
   id options = [NSClassFromString(@"UIAccessibilityElementTraversalOptions")
       voiceOverOptionsIncludingElementsFromOpaqueProviders:YES
                                               honorsGroups:NO];
+  if (![application respondsToSelector:@selector
+                    (_accessibilityLeafDescendantsWithOptions:)]) {
+    return @[];
+  }
   NSArray<NSObject*>* const allyNodes = [[application
       _accessibilityLeafDescendantsWithOptions:options] mutableCopy];
 
@@ -78,6 +93,27 @@
   return uidNode;
 }
 
+static BOOL _loadAccessibilityFramework(void) {
+  static BOOL isAccessibilityFrameworkLoaded;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    NSURL* const knownFrameworkUrl =
+        [NSBundle bundleForClass:UIApplication.class].bundleURL;
+    if (!knownFrameworkUrl) {
+      isAccessibilityFrameworkLoaded = NO;
+    } else {
+      NSURL* const accessibilityFrameworkUrl =
+          [knownFrameworkUrl.URLByDeletingLastPathComponent
+                  .URLByDeletingLastPathComponent
+              URLByAppendingPathComponent:
+                  @"PrivateFrameworks/UIAccessibility.framework"];
+      isAccessibilityFrameworkLoaded =
+          [[NSBundle bundleWithURL:accessibilityFrameworkUrl] load];
+    }
+  });
+  return isAccessibilityFrameworkLoaded;
+}
+
 static NSString* _nameForNode(NSObject* node) {
   NSMutableArray* const parts = [NSMutableArray new];
   if (node.accessibilityLabel.length > 0) {