[marshal methods] Make AndroidEnvironmentInternal.UnhandledException …

[grendello]

…public

Fixes: #10602
Context: 8bc7a3e

This is in the category of "how the hell has it worked before?", as every time the AndroidEnvironmentInternal.UnhandledException method living in Mono.Android.Runtime.dll would be called, the runtime would respond with a method not accessible exception, rightly so as both the type and the method were internal and visible only to Mono.Android.dll.

I guess we haven't had many unhandled exceptions in marshal method wrappers over the years?

This PR fixes the problem by making both the type and the method public. This is the simplest way to fix the issue.

[jonathanpeppers]

Can we write some Mono.Cecil code to make this public at build time? So, no one can use it at C# compile time?

This would happen in the marshal methods MSBuild steps, if they run.

[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[jonathanpeppers]

Did you find you needed this before this PR was green?

Is it because the .dll files are still open, such as here:

• 974a5ab#diff-ad297fa317310f786c3bbf13c1827e0d5ce2b6eee08c2ce3f9dfd657c21878a7R267-R276

[grendello]

Yeah, it would hit the sharing violation exception from time to time. It might be due to the code you pointed to, but fixing this should be done in a separate PR.

[Copilot]

Pull request overview

This PR fixes issue #10602 where marshal method wrappers crash with a MethodAccessException when trying to call AndroidEnvironmentInternal.UnhandledException. The method and its containing type were internal, making them inaccessible from generated marshal method wrapper code.

Changes:

• Makes the UnhandledException method public in the source code
• Adds a new MSBuild task that modifies the Mono.Android.Runtime.dll assembly at build time to make the AndroidEnvironmentInternal type public
• Refactors file handling utilities in MarshalMethodsAssemblyRewriter to reusable helper methods

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
src/Mono.Android.Runtime/Android.Runtime/AndroidEnvironmentInternal.cs	Makes the UnhandledException method public (class remains internal in source)
src/Xamarin.Android.Build.Tasks/Tasks/FixUpMonoAndroidRuntime.cs	New MSBuild task that identifies Mono.Android.Runtime.dll and applies the fixup
src/Xamarin.Android.Build.Tasks/Utilities/MonoAndroidRuntimeMarshalMethodsFixUp.cs	New utility that uses Mono.Cecil to modify the assembly and make AndroidEnvironmentInternal type public
src/Xamarin.Android.Build.Tasks/Utilities/MonoAndroidHelper.cs	Adds reusable file copy and delete helper methods
src/Xamarin.Android.Build.Tasks/Utilities/MarshalMethodsAssemblyRewriter.cs	Refactored to use the new helper methods for file operations
src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets	Registers and invokes the new FixUpMonoAndroidRuntime task before RewriteMarshalMethods
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs	Adds test to verify the type becomes public after the fixup

[jonathanpeppers]

@grendello today I learned about [assembly: IgnoresAccessChecksToAttribute ("Mono.Android")]:

• https://github.com/search?q=repo%3Adotnet%2Fruntime+IgnoresAccessChecksToAttribute&type=code

This appears to be a runtime feature, that Mono even implements? I can't find docs on it, though.

Can we simply stamp this attribute on every assembly? It could probably be done in the existing MSBuild tasks that write the marshal methods?

[grendello]

@grendello today I learned about [assembly: IgnoresAccessChecksToAttribute ("Mono.Android")]:

* https://github.com/search?q=repo%3Adotnet%2Fruntime+IgnoresAccessChecksToAttribute&type=code

This appears to be a runtime feature, that Mono even implements? I can't find docs on it, though.

Yeah, it appears to be undocumented which has me worried a bit. Mono does have support for it in https://github.com/dotnet/runtime/blob/0bbe2a937db7b916ca94849de3a3d16f23f8b17f/src/mono/mono/metadata/assembly.c#L1707-L1710

The comment there appears to suggest it might be meant only for dynamically generated modules?

Can we simply stamp this attribute on every assembly? It could probably be done in the existing MSBuild tasks that write the marshal methods?

TBH, there's too much uncertainty about this attribute and its role. I wouldn't feel comfortable using it. It also appears to be a nuclear solution to the problem - it would essentially let anyone access anything in our assemblies, thus potentially creating maintenance problems for the future (people could start relying on internals being there because of that attribute)