[ios] presence of a semantics action affects platform view positioning #150030

Adding a SemanticsAction to an ancestor node of an iOS platform view can cause the platform view to be incorrectly positioned.

To reproduce:

• Basics
  • Setup your local environment for iOS development (e.g. install Xcode)
  • cd dev/integration_tests/ios_platform_view_tests
  • open ios/Runner.xcworkspace in Xcode
  • Open PlatformViewUITests
• Passing configuration:
  • Run the test as is
  • Witness the test passing
• On this line wrap UiKitView in a Semantics widget adding it any non-scrolling action (adjusting const as needed), say, onIncrease, like so:

            child: Semantics(
              onIncrease: () {},
              child: UiKitView(viewType: 'platform_text_field'),
            ),

• Rerun the test in Xcode
• Witness the test failing on this line with the following error:

Failed to failed to scroll to visible (by AX action) TextField, {{46.5, 115.0}, {300.0, 50.0}}, identifier: 'platform_view[0]', value: Platform Text Field, error: Error kAXErrorCannotComplete performing AXAction kAXScrollToVisibleAction on element AX element pid: 88534, elementOrHash.elementID: 4546916864.36. (Underlying Error: Error kAXErrorCannotComplete performing AXAction kAXScrollToVisibleAction on element AX element pid: 88534, elementOrHash.elementID: 4546916864.36)

Breadcrumbs:

• The problem starts with this line, where the presence of an action alters the value if isFocusable.
• From @jmagman: the problem manifests as an incorrectly positioned platform view.
• From @jmagman: detailed instructions for how to repro with a custom engine build.

Expected behavior

Simply adding an action to an ancestor of a platform view should not alter the platform view's position on the screen.