fix(apple): Load tunnel manager after creating it

[jamilbk]

When launching Firezone for the first time, the VPN profile doesn't exist. We prompt the user to create it with "Grant VPN Permission", but then we fail to reload it, which initializes the tunnelManager instance variables properly and binds observers.

The result of this was that we failed to react to VPN status changes on the first launch of Firezone.

This can (and should be) refactored to be cleaner, but that is out of scope for this PR and will be saved for #6554.

Refs #7579

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Name	Status	Preview	Comments	Updated (UTC)
firezone	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Dec 30, 2024 6:56pm

[thomaseizinger]

I don't know Swift very well. What is the point of spawning a task inside a dispatch queue? Those sound like equivalent things?

[jamilbk]

Good question. DispatchQueue.main.async takes a synchronous function as its argument, so we need to wrap the call to TunnelManager.shared.create() with a Task.

However, I think it makes more sense to flip these around like so:

  func createVPNProfile() {
    Task {
      try await TunnelManager.shared.create()

      DispatchQueue.main.async { [weak self] in
        guard let self else { return }
        
        // Load the new settings and bind observers
        self.loadTunnelManager()
      }
    }
  }

[thomaseizinger]

Task itself spawns, right? In other words, the task starts executing as soon as the task is created. So it seems redundant here?

[jamilbk]

They serve different purposes -- Task creates an async context which starts executing immediately, but without any guarantees on which thread.

DispatchQueue.main queues the function to execute asynchronously on the main thread, where it's required to be for UI updates. Because the self.loadTunnelManager function updates the UI and binds the tunnel manager updates to the MenuBar / UI views, that needs to happen on the main thread.

[jamilbk]

And since the function passed to DispatchQueue.main.async must be synchronous, we can't call try await TunnelManager.shared.create() directly in that block.

Hmm, actually, since this is the only place where that async function is called, maybe I can just make it blocking. Let me see.