From 21d86c09af54475b48cd3c12ffddd573aec087a1 Mon Sep 17 00:00:00 2001
From: Sash Zats <zats@meta.com>
Date: Thu, 21 Sep 2023 10:14:43 -0700
Subject: [PATCH] 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
---
 .../Serializers/UIDInitEvent+Foundation.m     | 10 ++++--
 .../Traversal/UIDAllyTraversal.h              |  2 ++
 .../Traversal/UIDAllyTraversal.m              | 36 +++++++++++++++++++
 3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Serializers/UIDInitEvent+Foundation.m b/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Serializers/UIDInitEvent+Foundation.m
index 9b6eb5065..89a2c1b27 100644
--- a/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Serializers/UIDInitEvent+Foundation.m
+++ b/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),
   };
 }
 
diff --git a/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.h b/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.h
index 95c17a457..4f97a2e79 100644
--- a/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.h
+++ b/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;
 
diff --git a/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.m b/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.m
index 040a8e98b..7e0ed379d 100644
--- a/iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Traversal/UIDAllyTraversal.m
+++ b/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) {