Microsoft.NET.Sdk.Web global using statements break Serilog/NLog/log4net consumers on upgrade

From https://github.com/dotnet/templating/issues/3359#issuecomment-914693605

The .NET 6 version of Microsoft.NET.Sdk.Web introduces a default global using statement for Microsoft.Extensions.Logging. This brings MEL’s ILogger into scope everywhere, breaking existing code that uses Serilog’s (or another framework’s) ILogger interface, with errors like:

/home/pi/dl/nix/seq/tmp/ubuntu.20.04-arm64/src/Seq/Server/Tasks/TaskRunner.cs(15,18): error CS0104: 'ILogger' is an ambiguous reference between 'Microsoft.Extensions.Logging.ILogger' and 'Serilog.ILogger' [/home/pi/dl/nix/seq/tmp/ubuntu.20.04-arm64/src/Seq/Seq.csproj]

The breakage can be worked around by adding <EnableDefaultGlobalUsing>false</EnableDefaultGlobalUsing> or similar to the project’s CSPROJ file, but this is a pretty nasty papercut that penalizes users for choosing a logging library other than Microsoft’s. The chore will be particularly onerous because of the number of projects affected (and volume of errors within these projects).

I’d also expect that many users will turn to the Serilog project asking for guidance or reporting the breakage as a bug, since the default assumption people make when encountering an issue like this is that “Serilog is broken on .NET 6” - which increases our support burden 😃

CC @DamianEdwards

[davidfowl]

This might be another alternative:

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Serilog.Extensions.Hosting" Version="4.1.2" />
  </ItemGroup>

  <ItemGroup>
    <Using Include="Serilog.ILogger" Alias="ILogger" />
  </ItemGroup>

</Project>

OR

global using ILogger = Serilog.ILogger;

using Serilog;

var builder = WebApplication.CreateBuilder(args);
builder.Host.UseSerilog();
var app = builder.Build();

app.MapGet("/", (ILogger logger) => "Hello World!");

app.Run();

Tell customers to introduce a global alias for serilog’s ILogger as an override. (This can also be scoped to a file if that is too global).

[swythan]

Note that some users (e.g. my team) use Serilog as an output system, but use Microsoft.Extensions.Logging abstractions for most of the actual logging. It would be confusing to deal with the NuGet reference to Serilog causing ILogger to be switched from one definition to the other.

That said; I’ll probably be disabling global usings everywhere, anyway.