From dca7480bd3f9acdffa8ac2dffc94c2845b8bd6e2 Mon Sep 17 00:00:00 2001
From: Michael Goderbauer <goderbauer@google.com>
Date: Wed, 20 Sep 2017 14:17:50 -0700
Subject: [PATCH] Don't crash on iOS if there is only a single SemanticsNode
 (flutter/engine#4128)

* Don't crash if there is only a single SemanticsNode

Previously, the code assumed that the root SemanticsNode will allways have a child. This is not true as can be seen in the hello_world example app, which would crash when a11y is turned on.

* review comment
---
 .../darwin/ios/framework/Source/accessibility_bridge.mm        | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm b/engine/src/flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm
index 06135d426c..9953ebdf57 100644
--- a/engine/src/flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm
+++ b/engine/src/flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm
@@ -206,11 +206,12 @@ bool GeometryComparator(SemanticsObject* a, SemanticsObject* b) {
 #pragma mark - UIAccessibilityElement protocol
 
 - (id)accessibilityContainer {
-  if ([self hasChildren]) {
+  if ([self hasChildren] || _uid == kRootNodeId) {
     if (_container == nil)
       _container = [[SemanticsObjectContainer alloc] initWithSemanticsObject:self bridge:_bridge];
     return _container;
   }
+  NSAssert(_parent != nil, @"Illegal access to non-existent parent of root semantics node");
   return [_parent accessibilityContainer];
 }