Logging Source Generator fails to compile due to CS8795 error with file-scoped namespaces

[martincostello]

Description

If a class used to provide the partial methods for the Logging Source Generator uses file-scoped namespaces, the project fails to compile with errors similar to the below.

Project\Logger.cs(11,36): error CS8795: Partial method 'Logger.Greeting(ILogger, string)' must have an implementation part because it has accessibility modifiers. [Project\Project.csproj]
Project\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,36): error CS0759: No defining declaration found for implementing declaration of partial method 'Logger.Greeting(ILogger, string)' [Project\Project.csproj]

Minimal repro

Project.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0-rc.1.21420.7" />
    <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0-rc.1.21420.7" />
    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.0-rc.1.21420.7" />
  </ItemGroup>
</Project>

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using MyLibrary;

using var serviceProvider = new ServiceCollection()
    .AddLogging(builder => builder.AddConsole())
    .BuildServiceProvider();

var loggerFactory = serviceProvider.GetRequiredService<ILoggerFactory>();
var logger = loggerFactory.CreateLogger("MyLogger");

Logger.Greeting(logger, "World");

Logger.cs

using Microsoft.Extensions.Logging;

namespace MyLibrary;

internal partial class Logger
{
    [LoggerMessage(EventId = 1, Level = LogLevel.Information, Message = "Hello {Name}!")]
    public static partial void Greeting(ILogger logger, string name);
}

Expected Output

Project> dotnet run
info: MyLogger[1]
      Hello World!

Configuration

.NET SDK 6.0.100-rc.1.21420.39
Microsoft.Extensions.Logging 6.0.0-rc.1.21420.7

Regression?

No.

[ghost]

Tagging subscribers to this area: @maryamariyan
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

If a class used to provide the partial methods for the Logging Source Generator uses file-scoped namespaces, the project fails to compile with errors similar to the below.

Project\Logger.cs(11,36): error CS8795: Partial method 'Logger.Greeting(ILogger, string)' must have an implementation part because it has accessibility modifiers. [Project\Project.csproj]
Project\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,36): error CS0759: No defining declaration found for implementing declaration of partial method 'Logger.Greeting(ILogger, string)' [Project\Project.csproj]

Minimal repro

Project.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0-rc.1.21420.7" />
    <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0-rc.1.21420.7" />
    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.0-rc.1.21420.7" />
  </ItemGroup>
</Project>

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using MyLibrary;

using var serviceProvider = new ServiceCollection()
    .AddLogging(builder => builder.AddConsole())
    .BuildServiceProvider();

var loggerFactory = serviceProvider.GetRequiredService<ILoggerFactory>();
var logger = loggerFactory.CreateLogger("MyLogger");

Logger.Greeting(logger, "World");

Logger.cs

using Microsoft.Extensions.Logging;

namespace MyLibrary;

internal partial class Logger
{
    [LoggerMessage(EventId = 1, Level = LogLevel.Information, Message = "Hello {Name}!")]
    public static partial void Greeting(ILogger logger, string name);
}

Expected Output

Project> dotnet run
info: MyLogger[1]
      Hello World!

Configuration

.NET SDK 6.0.100-rc.1.21420.39
Microsoft.Extensions.Logging 6.0.0-rc.1.21420.7

Regression?

No.

Author:	martincostello
Assignees:	-
Labels:	untriaged, area-Extensions-Logging
Milestone:	-

[ghost]

Potential fix in LoggerMessageGenerator.Parser.cs line 410 :

// determine the namespace the class is declared in, if any
SyntaxNode? potentialNamespaceParent = classDec.Parent;
- while (potentialNamespaceParent != null && potentialNamespaceParent is not NamespaceDeclarationSyntax)
+ while (potentialNamespaceParent != null &&
+    potentialNamespaceParent is not NamespaceDeclarationSyntax &&
+    potentialNamespaceParent is not FileScopedNamespaceDeclarationSyntax)
{
    potentialNamespaceParent = potentialNamespaceParent.Parent;
}
- if (potentialNamespaceParent is NamespaceDeclarationSyntax namespaceParent)
+ if (potentialNamespaceParent is BaseNamespaceDeclarationSyntax namespaceParent)
{

The type FileScopedNamespaceDeclarationSyntax seems to be available from Microsoft.CodeAnalysis.CSharp version 4.0.0-3.final

[davidfowl]

Seems like we should fix this for 6.0.0

cc @maryamariyan @ericstj @eerhardt

[martincostello]

I've opened a PR with the proposed fix #57880 (comment) in #57894.

[maryamariyan]

We merged the fix to main, will need to backport to 6.0.0 and test/fix for JSON if needed too.

/cc @layomia

[martincostello]

JSON seems fine: #57894 (comment)

[tarekgh]

Has been fixed by #57894