Xamarin-android: Linker Error because of System.String::TrimStart(System.Char)

[bgavrilMS]

Steps to Reproduce

1. Create a MonoAndroid 8.1 library and in one of the methods use String.TrimStart('#')
2. Create an XForms app and take a dependency on the the file from step 1
3. Configure the linker to anything but None
4. Build the xforms app using VS 15.8.* (this is the version currently on VSTS hosted builds). Still investigating on a VS for Mac repro.

Repro project (from step 2): https://github.com/Azure-Samples/active-directory-xamarin-native-v2

Expected Behavior

It should build;

Actual Behavior

C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2053,5): Error MSB4018: The "LinkAssemblies" task failed unexpectedly.
Mono.Linker.MarkException: Error processing method: 'Microsoft.Identity.Json.Schema.JsonSchema Microsoft.Identity.Json.Schema.JsonSchemaBuilder::ResolveReferences(Microsoft.Identity.Json.Schema.JsonSchema)' in assembly: 'Microsoft.Identity.Client.dll' ---> Mono.Cecil.ResolutionException: Failed to resolve System.String System.String::TrimStart(System.Char)

at Mono.Linker.Steps.MarkStep.HandleUnresolvedMethod(MethodReference reference)
at Mono.Linker.Steps.MarkStep.MarkMethod(MethodReference reference)
at Mono.Linker.Steps.MarkStep.MarkInstruction(Instruction instruction)
at Mono.Linker.Steps.MarkStep.MarkMethodBody(MethodBody body)
at Mono.Linker.Steps.MarkStep.ProcessMethod(MethodDefinition method)
at Mono.Linker.Steps.MarkStep.ProcessQueue()
--- End of inner exception stack trace ---
at Mono.Linker.Steps.MarkStep.ProcessQueue()
at Mono.Linker.Steps.MarkStep.ProcessPrimaryQueue()
at Mono.Linker.Steps.MarkStep.Process()

Version Information

VisualStudio for Win 15.8.7 (current version of VSTS Hosted 2017)
Will update this issue with version info for VS for MAC

Impact

This is causing many failures in the CI builds of many people. See https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/745

If a linker is not used, a MethodMissingException occurs: https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/744

Please do not close this issue because the latest version of VS is not used. We need to understand the root cause first.

Possible cause

I think that when building the library at step 1, the build will use a reference assembly that has 2 methods:

String.Trim(char) // --> library will be compiled against this
String.Trim(param char[]) // --> the linker / runtime only has access to this method

However the runtime / the linker only has access to String.Trim(param char[]) (maybe from here? https://github.com/mono/mono/blob/master/mcs/class/referencesource/mscorlib/system/string.cs#L1286)

[SergeBerwert]

I have the same problem with build on AppCenter

[LeversonCarlos]

Same here. Local build with VS 15.9.0 works fine. AppCenter fails.

[mikerunnals]

I also have this same problem using the with build pipeline on AppCenter with the Microsoft-hosted agents
https://github.com/Microsoft/azure-pipelines-image-generation/blob/master/images/macos/macos-Readme.md#xamarin

[bgavrilMS]

Is anyone from Xamarin triaging issues?

[Abdulbasha]

i Updated the Microsoft.Identity.Client to 2.7.0. Still we are facing the same issue in VSTS / Devops. But luckily its working properly in VS in Mac. But facing issue in VSTS. Any update on this issue ?

[bgavrilMS]

@Abdulbasha - I contacted VSTS - they hope to upgrade the hosted agent images by end of this month. You could use a local VSTS agent until then or an older version of MSAL.

[LeversonCarlos]

Hi folks.
I've managed it to work on appCenter by changing (on build configuration) the SDK Version from Xamarin Android 9.0 to Xamarin Android 9.1 (with uses Mono 5.16). Cant say about Xamarin IOS.
But hope it helps someone else.

[dansiegel]

4-1/2 months no comment from anyone on the Android team... seriously? I have to reiterate the question from @bgavrilMS

Is anyone from Xamarin triaging issues?

cc: @JonDouglas @jonathanpeppers

[jonathanpeppers]

@dansiegel I think the problem here was AppCenter needs to update Xamarin.Android?

From LeversonCarlos:

Same here. Local build with VS 15.9.0 works fine. AppCenter fails.

@bgavrilMS were you able to solve your issue on AppCenter? maybe we can close this?

[devlead]

For me it got sorted by picking newer Xamarin Android with newer mono version on AppCenter

[jonathanpeppers]

@bgavrilMS let us know if you are still have a problem. Closing for now, thanks!