Logging-Generator doesn't use LoggerMessage.Define for > 1 template argument #51917
Description
If the template has one argument, then (as expected) LoggerMessage.Define use used. But for > 1 argument it emits the struct-based code.
For the tests I used
<PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0-preview.4.21216.3" />Repro:
public static partial class Log
{
[LoggerMessage(EventId = 1, Level = LogLevel.Information, Message = "Hello {Name}")]
public static partial void Greet(this ILogger logger, string name);
[LoggerMessage(EventId = 2, Level = LogLevel.Information, Message = "Hello {Name} from {City}")]
public static partial void GreetWithCity(this ILogger logger, string name, string city);
}Generated code
// <auto-generated/>
#nullable enable
partial class Log
{
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.Extensions.Logging.Generators", "6.0.0.0")]
private static readonly global::System.Action<global::Microsoft.Extensions.Logging.ILogger, global::System.String, global::System.Exception?> __GreetCallback =
global::Microsoft.Extensions.Logging.LoggerMessage.Define<global::System.String>(global::Microsoft.Extensions.Logging.LogLevel.Information, new global::Microsoft.Extensions.Logging.EventId(1, nameof(Greet)), "Hello {Name}", true);
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.Extensions.Logging.Generators", "6.0.0.0")]
public static partial void Greet(this global::Microsoft.Extensions.Logging.ILogger logger, global::System.String name)
{
if (logger.IsEnabled(global::Microsoft.Extensions.Logging.LogLevel.Information))
{
__GreetCallback(logger, name, null);
}
}
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.Extensions.Logging.Generators", "6.0.0.0")]
private readonly struct __GreetWithCityStruct : global::System.Collections.Generic.IReadOnlyList<global::System.Collections.Generic.KeyValuePair<string, object?>>
{
private readonly global::System.String _name;
private readonly global::System.String _city;
public __GreetWithCityStruct(global::System.String name, global::System.String city)
{
this._name = name;
this._city = city;
}
public override string ToString()
{
var Name = this._name;
var City = this._city;
return $"Hello {Name} from {City}";
}
public static string Format(__GreetWithCityStruct state, global::System.Exception? ex) => state.ToString();
public int Count => 3;
public global::System.Collections.Generic.KeyValuePair<string, object?> this[int index]
{
get => index switch
{
0 => new global::System.Collections.Generic.KeyValuePair<string, object?>("Name", this._name),
1 => new global::System.Collections.Generic.KeyValuePair<string, object?>("City", this._city),
2 => new global::System.Collections.Generic.KeyValuePair<string, object?>("{OriginalFormat}", "Hello {Name} from {City}"),
_ => throw new global::System.IndexOutOfRangeException(nameof(index)), // return the same exception LoggerMessage.Define returns in this case
};
}
public global::System.Collections.Generic.IEnumerator<global::System.Collections.Generic.KeyValuePair<string, object?>> GetEnumerator()
{
for (int i = 0; i < 3; i++)
{
yield return this[i];
}
}
global::System.Collections.IEnumerator global::System.Collections.IEnumerable.GetEnumerator() => GetEnumerator();
}
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.Extensions.Logging.Generators", "6.0.0.0")]
public static partial void GreetWithCity(this global::Microsoft.Extensions.Logging.ILogger logger, global::System.String name, global::System.String city)
{
if (logger.IsEnabled(global::Microsoft.Extensions.Logging.LogLevel.Information))
{
logger.Log(
global::Microsoft.Extensions.Logging.LogLevel.Information,
new global::Microsoft.Extensions.Logging.EventId(2, nameof(GreetWithCity)),
new __GreetWithCityStruct(name, city),
null,
__GreetWithCityStruct.Format);
}
}
}I'd expect that LoggerMessage.Define is used when there are <= 6 template parameters iif they match the arguments of the method.
LoggerMessage.Define should be prefered. The struct based variant needs to allocate a new formatting delegate (for __GreetWithCityStruct.Format) on each call.
/cc: @maryamariyan