[Proposal] Add adapter for `TaskLoggingHelper` and `ILogger`

[premun]

Context

A common setup that we have is that we have some business logic in some library. We want to then call into this logic from different entrypoints:

• CLI tool
• Web service
• MSBuild tasks

The usual way to approach this is to use Microsoft.Extensions.DependencyInjection to build the classes and Microsoft.Extensions.Logging.ILogger for generic logging. Then, in various environments, we inject the right logger:

• The CLI will usually plug in the console logger via .AddConsole()
• The web service can for instance make the service log into Application Insights via .AddApplicationInsightsTelemetry()

The MSBuild environment uses the Microsoft.Build.Utilities.Task.Log member (TaskLoggingHelper class) but it is not possible to plug this well together with the ILogger interface that is quite native to .NET these days.

Goal

Ideally, similarly to the other options, we would have:

• [ ] An adapter that would get an instance of the TaskLoggingHelper as a parameter and would implement the ILogger interface.
• [ ] An easy way how to inject task's Log as the ILogger interface through the dependency injection.

The adapter should ideally adhere to verbosity rules and similar setting.

Example

Something like this comes to mind:

public class CustomTask : Task
{
    private readonly IServiceProvider _serviceProvider;

    public VirtualMonoRepo_Initialize()
    {
        _serviceProvider = CreateServiceProvider();
    }

    public override bool Execute()
    {
        var myCustomLogic = _serviceProvider.GetRequiredService<IBusinessLogic>();
        return myCustomLogic.DoSomething();
    }

    private IServiceProvider CreateServiceProvider() =>
          new ServiceCollection()
                .AddBusinessLogic()  // this registers my app's classes into DI
                .AddTaskLogging(Log) // this registers current task's logger as ILogger
                .BuildServiceProvider();
}

[KalleOlaviNiemitalo]

Would the logger expect the state object to implement IReadOnlyCollection<KeyValuePair<string, object>>, and then recognise keys such as "Subcategory", "File", "LineNumber"?

[premun]

Honestly, I didn't think this 100% through as I don't know the specifics of the TaskLoggingHelper so I'd imagine this could a subject to further specification. I only know, I've tried a similar setup like this and had a bit hacky quick way to achieve this rather than a proper solution. I might clean up the code and share it here later if I have time.

[premun]

@matkoch I was wondering whether you have dealt with this situation?

[KalleOlaviNiemitalo]

I have implemented something related: logging interfaces and classes that can output to a SARIF 2.1.0 file or to MSBuild-compatible Console.Error. I don't think Microsoft.Extensions.Logging.ILogger would have been a good fit for that; it seems more suitable for logging in which the logger provider does not understand the semantics of the data structures and just needs to serialize them somewhere for later processing.

[premun]

I just found another .NET team that has implemented roughly the same as what I need/had in mind: https://github.com/dotnet/templating/blob/fedcb3c6e2eeafd13822f10ec4f0b8d0576c7af5/tools/Microsoft.TemplateEngine.Authoring.Tasks/Utilities/MSBuildLogger.cs

[baronfel]

When this is tackled, this blog is a great resource for how we should tackle the 'BeginScope' implementation.