[LSG] Logging Source Generator fails to compile when out parameter modifier is present

[maryamariyan]

As part of issue #62644 we fixed compile errors with using ref or in.

But for out usage, we would need to add a diagnostic that explains out usage is not supported for LoggerMessageAttribute annotated logging methods.

Proposal

The proposed diagnostic descriptor would be:

        public static DiagnosticDescriptor InvalidLoggingMethodParameterOut { get; } = new DiagnosticDescriptor(
            id: "SYSLIB1024",
            title: new LocalizableResourceString(nameof(SR.InvalidLoggingMethodParameterOutTitle), SR.ResourceManager, typeof(FxResources.Microsoft.Extensions.Logging.Generators.SR)),
            messageFormat: new LocalizableResourceString(nameof(SR.InvalidLoggingMethodParameterOutMessage), SR.ResourceManager, typeof(FxResources.Microsoft.Extensions.Logging.Generators.SR)),
            category: "LoggingGenerator",
            DiagnosticSeverity.Error,
            isEnabledByDefault: true);

With the following title:

Argument is using the unsupported out parameter modifier

And the following message format:

Argument '{0}' is using the unsupported out parameter modifier

Code Sample

IReadOnlyList<Diagnostic> diagnostics = await RunGenerator(@$"
                partial class C
                {{
                    [LoggerMessage(EventId = 0, Level = LogLevel.Debug, Message = ""Parameter {{P1}}"")]
                    static partial void M(ILogger logger, out int p1);
                }}");

Assert.Single(diagnostics);
Assert.Equal(DiagnosticDescriptors.InvalidLoggingMethodParameterOut.Id, diagnostics[0].Id);

TODO:

• Take diagnostic message/severity/category to API review

[ghost]

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Issue Details

---

As part of issue #62644 we fixed compile errors with using ref or in.

But for out usage, we would need to add a diagnostic that explains out usage is not supported for LoggerMessageAttribute annotated logging methods.

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

[allantargino]

Hi @maryamariyan, I'd like to be assigned to this one :)

[allantargino]

The proposed diagnostic descriptor would be:

        public static DiagnosticDescriptor InvalidLoggingMethodParameterOut { get; } = new DiagnosticDescriptor(
            id: "SYSLIB1024",
            title: new LocalizableResourceString(nameof(SR.InvalidLoggingMethodParameterOutTitle), SR.ResourceManager, typeof(FxResources.Microsoft.Extensions.Logging.Generators.SR)),
            messageFormat: new LocalizableResourceString(nameof(SR.InvalidLoggingMethodParameterOutMessage), SR.ResourceManager, typeof(FxResources.Microsoft.Extensions.Logging.Generators.SR)),
            category: "LoggingGenerator",
            DiagnosticSeverity.Error,
            isEnabledByDefault: true);

With the following title:

Argument is using the unsupported out parameter modifier

And the following message format:

Argument '{0}' is using the unsupported out parameter modifier

[tarekgh]

@allantargino feel free to submit a PR for that and I can help reviewing. Thanks for willing to help with this issue.

[tarekgh]

Forgot to mention, we need to do "Take diagnostic message/severity/category to API review" first. I'll try to edit the issue description and then take it to the API review first. Please hold creating the PR till we get the design review approval.

[allantargino]

Thanks @tarekgh. I just updated the proposal in my comment above to have both message title and format (instead of just message format). Would you please update the description? Thanks!

[tarekgh]

With the following message format:

Did you mean this will be the title?

[allantargino]

Yes, my bad 😄 I just updated it again.

[terrajobst]

Video

Looks good as proposed.