Prevent Race Condition Allowing Simultaneous Calling of Navigation.PushModalAsync() / Shell.GotoAsync() in PopupExtensions

[TheCodeTraveler]

Description of Change

This PR fixes the race condition where PopupExtensions could call Navigation.PushModalAsync() / Shell.GotoAsync() to display a Popup while a previously-called Navigation.PushModalAsync() / Shell.GotoAsync() could actively be running.

To avoid this race condition, I added SemaphoreSlim showPopupSemaphoreSlim = new(1, 1); and now call showPopupSemaphoreSlim.WaitAsync() before each Navigation.PushModalAsync() / Shell.GotoAsync() method call. This ensures we wait until the modal page has finished pushing before we ask MAUI to push a new modal page.

Linked Issues

• Fixes [BUG] Concurrently produced popups cannot be closed (iOS) #3192

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard

Additional information

This is more likely a bug internally in MAUI, as this SemaphoreSlim is not needed on Android.

[Copilot]

Pull request overview

This PR addresses a race condition when multiple popups are shown concurrently by serializing popup navigation so PushModalAsync() / Shell.GoToAsync() calls don’t overlap.

Changes:

• Added a shared SemaphoreSlim to gate popup display navigation.
• Wrapped INavigation.PushModalAsync(...) and Shell.GoToAsync(...) calls with semaphore WaitAsync() / Release().

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.