dotnet watch fails when targeting sandboxed maccatalyst apps

[vitek-karas]

This was tested using .NET 11 Preview 5.

dotnet new maui
dotnet watch -> select net11.0-maccatalyst

On mono it fails with:

=================================================================
	Native Crash Reporting
=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================

=================================================================
	Native stacktrace:
=================================================================
	0x100748150 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_dump_native_crash_info
	0x1006ff620 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_handle_native_crash
	0x1008de844 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : sigabrt_signal_handler.cold.1
	0x100747a14 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_runtime_setup_stat_profiler
	0x1854e3744 - /usr/lib/system/libsystem_platform.dylib : _sigtramp
	0x1854d98d8 - /usr/lib/system/libsystem_pthread.dylib : pthread_kill
	0x1853e0644 - /usr/lib/system/libsystem_c.dylib : abort
	0x1004e0e78 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : xamarin_register_assembly
	0x1004e12b0 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : xamarin_print_all_exceptions_wrapper
	0x1004e4388 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : xamarin_print_all_exceptions
	0x1004e4a4c - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : xamarin_unhandled_exception_handler
	0x100600424 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_invoke_unhandled_exception_hook
	0x1006ff4bc - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_handle_exception_internal
	0x1006fdb20 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_handle_exception
	0x100744734 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_arm_throw_exception
	0x1004b057c - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : throw_exception
	0x1006491e8 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mono_runtime_run_startup_hooks
	0x100697888 - /Users/<user>/repro/maui/mp5debug/bin/Debug/net11.0-maccatalyst/maccatalyst-arm64/mp5debug.app/Contents/MacOS/mp5debug : mini_init

On CoreCLR it fails with:

Unhandled exception. System.ArgumentException: Startup hook assembly '/Users/<user>/.dotnet.install/11.0.P5/sdk/11.0.100-preview.5.26302.115/DotnetTools/dotnet-watch/11.0.100-preview.5.26302.115/tools/net11.0/any/hotreload/net10.0/Microsoft.Extensions.DotNetDeltaApplier.dll' failed to load. See inner exception for details.
 ---> System.IO.FileLoadException: Could not load file or assembly '/Users/<user>/.dotnet.install/11.0.P5/sdk/11.0.100-preview.5.26302.115/DotnetTools/dotnet-watch/11.0.100-preview.5.26302.115/tools/net11.0/any/hotreload/net10.0/Microsoft.Extensions.DotNetDeltaApplier.dll'. Access is denied.

File name: '/Users/<user>/.dotnet.install/11.0.P5/sdk/11.0.100-preview.5.26302.115/DotnetTools/dotnet-watch/11.0.100-preview.5.26302.115/tools/net11.0/any/hotreload/net10.0/Microsoft.Extensions.DotNetDeltaApplier.dll'
   at System.Runtime.Loader.AssemblyLoadContext.LoadFromPath(IntPtr ptrNativeAssemblyBinder, String ilPath, String niPath, ObjectHandleOnStack retAssembly)
   at System.Runtime.Loader.AssemblyLoadContext.LoadFromAssemblyPath(String assemblyPath)
   at System.StartupHookProvider.CallStartupHook(StartupHookNameOrPath startupHook)
   --- End of inner exception stack trace ---
   at System.StartupHookProvider.CallStartupHook(StartupHookNameOrPath startupHook)
   at System.StartupHookProvider.ProcessStartupHooks(String diagnosticStartupHooks)
   at System.StartupHookProvider.ManagedStartup(Char* pDiagnosticStartupHooks, Exception* pException)

This only happens on maccatalyst - using iOS simulator works.

[rolfbjarne]

Unhandled exception. System.ArgumentException: Startup hook assembly '/Users//.dotnet.install/11.0.P5/sdk/11.0.100-preview.5.26302.115/DotnetTools/dotnet-watch/11.0.100-preview.5.26302.115/tools/net11.0/any/hotreload/net10.0/Microsoft.Extensions.DotNetDeltaApplier.dll' failed to load. See inner exception for details.
---> System.IO.FileLoadException: Could not load file or assembly '/Users//.dotnet.install/11.0.P5/sdk/11.0.100-preview.5.26302.115/DotnetTools/dotnet-watch/11.0.100-preview.5.26302.115/tools/net11.0/any/hotreload/net10.0/Microsoft.Extensions.DotNetDeltaApplier.dll'. Access is denied.

This is because the Mac Catalyst app is in sandbox mode (the default). Disabling sandbox mode (in Platforms/MacCatalyst/Entitlements.plist) gets passed this, and then another error shows up, which is due to the trimmer being enabled (already filed here: #25295). If that's fixed too (by setting MtouchLink=None in the csproj), dotnet watch works for me.

Disabling the linker also makes it work when using Mono, so I'll leave this issue for the sandbox problem.

[rolfbjarne]

Presumably the sandbox problem also exists for macOS apps, the difference is that the sandbox isn't enabled by default for macOS apps.

[rolfbjarne]

The fix might actually be related to the fix for #25408, because the fix for both would be to:

• add the hot reload assembly to the app
• redirect/rewrite arguments/env vars so that the app loads the hot reload assembly from the in-app location

Note that the sandbox isn't enforced for simulator apps, which is why this is not needed there.