How to introduce generic interface param to constructor

[paxhujing]

In asp.net core controller，inject ILogger into constructors

[gfraiteur]

Could you elaborate the question with a code example please?

[paxhujing]

[ApiController]
[Route("[controller]/[action]")]
public class TestController : ControllerBase
{
    private readonly ILogger _logger;

    public TestController(ILogger<TestController> logger)
    {
        _logger = logger;
    }
}

Usually we need to inject ILogger<XXX>
This pattern appears in many places, so i want to inject ILogger<XXX> as an aspect.

internal class LoggerAttribute : ConstructorAspect
{
    public override void BuildAspect(IAspectBuilder<IConstructor> builder)
    {
        //How to introduce 'ILogger<XXX>'
        base.BuildAspect(builder);
    }
}

[ApiController]
[Route("[controller]/[action]")]
[Logger]
public class TestController : ControllerBase
{
}

This code should be equivalent to the above

[Zu-Hy]

Hello,
This is a message to remind you that your request is pending and awaits your feedback.
Thank you
Zuzana

[gfraiteur]

The documentation for the case is here: https://doc.metalama.net/aspects/advising/introducing-constructor-parameters

[paxhujing]

public class LoggerAttribute : TypeAspect
{
    [Introduce(WhenExists = OverrideStrategy.Ignore)]
    private readonly ILogger _logger;

    public override void BuildAspect(IAspectBuilder<INamedType> builder)
    {
        Type type = typeof(ILogger<>).MakeGenericType(builder.Target.ToType());
        var constructors = builder.Target.Constructors;
        foreach (var constructor in constructors)
        {
            builder.Advice.IntroduceParameter(
                constructor,
                "logger",
                type,
                TypedConstant.Default(type),
                pullAction: (p, c) =>
                    PullAction.IntroduceParameterAndPull(
                        "logger",
                        TypeFactory.GetType(type),
                        TypedConstant.Default(type)
                        )
                );
            builder.Advice.AddInitializer(constructor,
                StatementFactory.Parse("_logger = logger;"));
        }
    }
}

[ApiController]
[Route("[controller]")]
[Logger]
public class WeatherForecastController : ControllerBase
{

}

I got a compilation error

Error LAMA0041 'LoggerAttribute.BuildAspect' threw 'NotSupportedException' when applied to 'WeatherForecastController': >Derived classes must provide an implementation. Exception details are in 'C:\Users\hj\AppData\Local\Temp\Metalama\CrashReports\0.5.51-preview\exception-f7902288-9791-40f0-8529-3843efc1370b.txt'. To >attach a debugger to the compiler, use the '-p:MetalamaDebugCompiler=True' command-line option. LobbyWebsite.Main D:\Documents\JQK\A9\A9Lobby\website.src\dev\LobbyWebsite\Src\LobbyWebsite.Main\Controllers\WeatherForecastController.cs 6

If do not use generic interfance ILogger<T>,it will compile successfully

    public override void BuildAspect(IAspectBuilder<INamedType> builder)
    {
        Type type = typeof(ILogger);
        //Type type = typeof(ILogger<>).MakeGenericType(builder.Target.ToType());
        ...
    }

and,there was another compilation error that confused me

    [Introduce(WhenExists = OverrideStrategy.Ignore)]
    private readonly ILogger _logger;

Error LAMA0611 Error CS0103 in code generated by aspect 'Logger': The name '_logger' does not exist in the current context LobbyWebsite.Main D:\Documents\JQK\A9\A9Lobby\website.src\dev\LobbyWebsite\Src\LobbyWebsite.Main\Controllers\WeatherForecastController.cs 42

if i change 'private' to 'public',it will compile successfully

[gfraiteur]

if i change 'private' to 'public',it will compile successfully

There is a bug indeed. Template members must be public, but you can change their visibility using a property of the [Template] attribute