🔒 Fix unsafe nonisolated construct in MapKitPlugin

[esenmx]

🔒 Security Fix: Remove unsafe 'nonisolated(unsafe)' construct during plugin registration

🎯 What: Removed nonisolated(unsafe) binding of registrar in MapKitPlugin.register(with:).
⚠️ Risk: The use of nonisolated(unsafe) bypassed Swift 6 compiler concurrency and memory safety checks for a shared resource during plugin initialization, potentially allowing data races or unsafe concurrent access if initialization semantics changed.
🛡️ Solution: registrar is safely passed and captured directly within MainActor.assumeIsolated { ... } without disabling compiler safety checks.

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PR created automatically by Jules for task 3499962934664309862 started by @esenmx

[google-labs-jules]

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[esenmx]

Closing: this change breaks every macOS consumer. Flutter's generated macos/Flutter/GeneratedPluginRegistrant.swift calls MapKitPlugin.register(with:) from a nonisolated global function compiled in Swift 5 mode, so making register main-actor-isolated fails with error: call to main actor-isolated static method 'register(with:)' in a synchronous nonisolated context (reproduced with flutter build macos --debug on Xcode 26.6 / Flutter 3.44.9 stable; base ba7857d builds green). CI passed only because it builds the iOS example, whose registrant is Objective-C and performs no Swift isolation checking.

The nonisolated(unsafe) binding is not a security issue: it rebinds a local non-Sendable reference that is consumed synchronously inside MainActor.assumeIsolated, which asserts main-thread at runtime. There is no shared mutable state or concurrent access; the existing comment and commit 6c298e3 document why Xcode 26 requires it.

There is no alternative shape to request: the plain deletion (this branch's first commit 71f2bb5) fails with MapKitPlugin.swift:19:27: error: sending 'registrar' risks causing data races, and a sending FlutterPluginRegistrar parameter cannot witness the FlutterPlugin requirement. The base design is forced by Flutter's macOS Swift registrant. (Separately, we will add a macOS build job to CI so this class of change is caught before review.)

[google-labs-jules]

Closing: this change breaks every macOS consumer. Flutter's generated macos/Flutter/GeneratedPluginRegistrant.swift calls MapKitPlugin.register(with:) from a nonisolated global function compiled in Swift 5 mode, so making register main-actor-isolated fails with error: call to main actor-isolated static method 'register(with:)' in a synchronous nonisolated context (reproduced with flutter build macos --debug on Xcode 26.6 / Flutter 3.44.9 stable; base ba7857d builds green). CI passed only because it builds the iOS example, whose registrant is Objective-C and performs no Swift isolation checking.

The nonisolated(unsafe) binding is not a security issue: it rebinds a local non-Sendable reference that is consumed synchronously inside MainActor.assumeIsolated, which asserts main-thread at runtime. There is no shared mutable state or concurrent access; the existing comment and commit 6c298e3 document why Xcode 26 requires it.

There is no alternative shape to request: the plain deletion (this branch's first commit 71f2bb5) fails with MapKitPlugin.swift:19:27: error: sending 'registrar' risks causing data races, and a sending FlutterPluginRegistrar parameter cannot witness the FlutterPlugin requirement. The base design is forced by Flutter's macOS Swift registrant. (Separately, we will add a macOS build job to CI so this class of change is caught before review.)

Understood. Thank you for the detailed explanation regarding macOS GeneratedPluginRegistrant.swift behavior and the runtime guarantees of MainActor.assumeIsolated. Acknowledging and stopping work on this task.