Supply services when configuring Serilog inline

[nblumhardt]

This change adds an overload to UseSerilog() that passes an IServiceProvider to the logger configuration callback:

.UseSerilog((hostingContext, services, loggerConfiguration) => loggerConfiguration
    .ReadFrom.Configuration(hostingContext.Configuration)
    .Enrich.FromLogContext()
    .WriteTo.SomeSink(services.GetRequiredService<ISomeDependency>()));

There's a lot we could do on top of this to improve UX, but this is the fundamental capability needed to get the ball rolling.

The initialization of Serilog in the "inline" scenario will now have a slightly different timing, but I don't think this will be noticeable for most consumers.

I've tested this manually in a couple of different configurations; I'd love for someone with the Hosting familiarity to help set up some better unit tests for it, but I think the need for this is such that we should get it out there and start iterating :-)

• Fixes Be consistent about registering Serilog's ILogger for DI #16
• Fixes How to use with sinks that depend on ConfigureServices being run first? serilog-aspnetcore#84
• Fixes Support dependency injection into sinks, enrichers, filters, etc. serilog-aspnetcore#141

[sungam3r]

Why is there now null?

[nblumhardt]

Thanks for the note, @sungam3r - it's because ILogger is already registered lazily above (line 156); I've added a comment 👍

[sungam3r]

I don’t understand why this hack is needed. Could you explain please?

[skomis-mm]

@sungam3r,
ILogger needs to be registered as singleton. The registration method on MEDI is factory (to be able to implement the title feature). Registering singleton with factory method is subject to automatic disposal of the instantiated object that is undesirable since the disposing of ILogger handled by SerilogLoggerFactory (passing dispose=true to it constructor).
AFAIC, all this ceremony needed to correctly handle preserverStaticLogger=false (to do Log.CloseAndFlush()) otherwise the disposal could be handled by the DI container itself..

[sungam3r]

Quite hard to understand to one who has no some background knowledge about all this stuff. I guessed that the library should consider all combinations of use. Maybe we should add your comment to the code? It’s hard to understand what’s going on without it.

[nblumhardt]

Added a comment paraphrasing Sergey's - thanks for the suggestion 👍

[skomis-mm]

👍