Logging Source Generator fails to compile using keyword parameters with @ prefixes

[martincostello]

Description

If a C# keyword is used as a parameter name for a [LoggerMessage] method using the logging source generator prefixed with an @, such as the example below, the application will fail to compile due to the source generator creating invalid C#.

[LoggerMessage(1, LogLevel.Information, "Event: {event}")]
public static partial void LogEvent(ILogger logger, object @event);

If the @ is included in the template to match the parameter, it will also fail to compile.

Reproduction Steps

Attempt to run the following program using .NET 6 RC2:

<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.2.21480.5" /> 
    <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0-rc.2.21480.5" />
    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.0-rc.2.21480.5" />
  </ItemGroup>
</Project>

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

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

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

Log.LogEvent(logger, new { foo = "bar" });

internal static partial class Log
{
    [LoggerMessage(1, LogLevel.Information, "Event: {event}")]
    public static partial void LogEvent(ILogger logger, object @event);
}

Expected behavior

The following text is printed to the console:

info: MyLogger[1]
      Event: { foo = bar }

Actual behavior

The application fails to compile:

C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,125): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(15,49): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,36): error CS0756: A partial method may not have multiple defining declarations [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(16,32): error CS8795: Partial method 'Log.LogEvent(ILogger, object)' must have an implementation part because it has accessibility modifiers. [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,36): error CS0111: Type 'Log' already defines a member called 'LogEvent' with the same parameter types [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(15,49): error CS0102: The type 'Log' already contains a definition for '' [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,125): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(15,49): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]

The build failed. Fix the build errors and run again

It also fails to compile if the code is changed to include the @ in the template:

C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(16,64): warning SYSLIB1015: Argument 'event' is not referenced from the logging message [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(15,6): error SYSLIB1014: Template '@event' is not provided as argument to the logging method [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,125): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(57,47): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,36): error CS0756: A partial method may not have multiple defining declarations [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(16,32): error CS8795: Partial method 'Log.LogEvent(ILogger, object)' must have an implementation part because it has accessibility modifiers. [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,20): error CS0501: 'Log.__LogEventStruct.__LogEventStruct(object)' must declare a body because it is not marked abstract, extern, or partial [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,64): error CS0065: 'Log.__LogEventStruct.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(13,36): error CS0065: 'Log.__LogEventStruct.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,36): error CS0111: Type 'Log' already defines a member called 'LogEvent' with the same parameter types [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(57,47): error CS0102: The type 'Log' already contains a definition for '' [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,125): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(57,47): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(13,36): error CS0102: The type 'Log.__LogEventStruct' already contains a definition for '' [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]

The build failed. Fix the build errors and run again.

Regression?

No.

Known Workarounds

Do not use a C# identifier prefixed with @ as a logger message method parameter.

Configuration

Output from dotnet --info:

.NET SDK (reflecting any global.json):
 Version:   6.0.100-rc.2.21505.57
 Commit:    ab39070116

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19043
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\

Host (useful for support):
  Version: 6.0.0-rc.2.21480.5
  Commit:  6b11d64e7e

Other information

No response

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

Issue Details

---

Description

If a C# keyword is used as a parameter name for a [LoggerMessage] method using the logging source generator prefixed with an @, such as the example below, the application will fail to compile due to the source generator creating invalid C#.

[LoggerMessage(1, LogLevel.Information, "Event: {event}")]
public static partial void LogEvent(ILogger logger, object @event);

If the @ is included in the template to match the parameter, it will also fail to compile.

Reproduction Steps

Attempt to run the following program using .NET 6 RC2:

<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.2.21480.5" />
	<PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0-rc.2.21480.5" />
	<PackageReference Include="Microsoft.Extensions.Logging.Console" Version="6.0.0-rc.2.21480.5" />
  </ItemGroup>
</Project>

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

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

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

Log.LogEvent(logger, new { foo = "bar" });

internal static partial class Log
{
    [LoggerMessage(1, LogLevel.Information, "Event: {event}")]
    public static partial void LogEvent(ILogger logger, object @event);
}

Expected behavior

The following text is printed to the console:

info: MyLogger[1]
      Event: { foo = bar }

Actual behavior

The application fails to compile:

C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,125): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(15,49): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,36): error CS0756: A partial method may not have multiple defining declarations [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(16,32): error CS8795: Partial method 'Log.LogEvent(ILogger, object)' must have an implementation part because it has accessibility modifiers. [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,36): error CS0111: Type 'Log' already defines a member called 'LogEvent' with the same parameter types [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(15,49): error CS0102: The type 'Log' already contains a definition for '' [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,125): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(15,49): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]

The build failed. Fix the build errors and run again

It also fails to compile if the code is changed to include the @ in the template:

C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(16,64): warning SYSLIB1015: Argument 'event' is not referenced from the logging message [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(15,6): error SYSLIB1014: Template '@event' is not provided as argument to the logging method [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,125): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(57,47): error CS0065: 'Log.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,36): error CS0756: A partial method may not have multiple defining declarations [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Program.cs(16,32): error CS8795: Partial method 'Log.LogEvent(ILogger, object)' must have an implementation part because it has accessibility modifiers. [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,20): error CS0501: 'Log.__LogEventStruct.__LogEventStruct(object)' must declare a body because it is not marked abstract, extern, or partial [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(11,64): error CS0065: 'Log.__LogEventStruct.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(13,36): error CS0065: 'Log.__LogEventStruct.': event property must have both add and remove accessors [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,36): error CS0111: Type 'Log' already defines a member called 'LogEvent' with the same parameter types [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(57,47): error CS0102: The type 'Log' already contains a definition for '' [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(50,125): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(57,47): error CS0708: '': cannot declare instance members in a static class [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]
C:\Coding\martincostello\LoggerMessageKeywords\Microsoft.Extensions.Logging.Generators\Microsoft.Extensions.Logging.Generators.LoggerMessageGenerator\LoggerMessage.g.cs(13,36): error CS0102: The type 'Log.__LogEventStruct' already contains a definition for '' [C:\Coding\martincostello\LoggerMessageKeywords\LoggerMessageKeywords.csproj]

The build failed. Fix the build errors and run again.

Regression?

No.

Known Workarounds

Do not use a C# identifier prefixed with @ as a logger message method parameter.

Configuration

Output from dotnet --info:

.NET SDK (reflecting any global.json):
 Version:   6.0.100-rc.2.21505.57
 Commit:    ab39070116

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19043
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\

Host (useful for support):
  Version: 6.0.0-rc.2.21480.5
  Commit:  6b11d64e7e

Other information

No response

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

[MichalBrylka]

I had similar issue. Seems that message template parser fails to recognize special meaning of "@" where it's well-known standard:
https://messagetemplates.org/

Tested with
<PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0" />

[MichalBrylka]

moreover it seems that @ is generally not supported well MS.Extensions.Logging
iLogger.LogInformation("TestController.Hello {@Person}", new Person("Mike", 30));
this simply calls ToString on Person class:
TestController.Hello Person { Name = Mike, Age = 30 }
Whereas Serilog handles that more nicely:

using Serilog;
Log.Logger = new LoggerConfiguration()
    .Enrich.FromLogContext()
    .WriteTo.Console()
    .CreateLogger();
Log.Logger.Warning("Person {Person}", new Person("Mike", 30));
//ToString is called: Person Person { Name = Mike, Age = 30 }


Log.Logger.Warning("Person properties {@Person}", new Person("Mike", 30));
//properties are being unpacked: Person properties {"Name": "Mike", "Age": 30, "$type": "Person"}

[sakno]

Related issue: serilog/serilog-extensions-logging#197
Related discussion: #61813

[MichalBrylka]

@maryamariyan can this issue be addresses in current version or we need to wait till NET 7.0 ?

[sakno]

@maryamariyan , I'm ready fix this in two steps:

• Servicing update for .NET 6 to correctly handle parameter names matching keywords in C#
• The second part requires to write a proposal and start API approval process

[maryamariyan]

This would be fixed in 7.0

[maryamariyan]

Closed #62572 as dupe of this. Would also need to consider support for parameter name prefixed with $ as mentioned in that issue.