Logging Source Generator fails to compile using keyword parameters with @ prefixes depending on the placeholder order

[luiscantero]

Description

The code below fails to compile depending on the order of the placeholders in the template. It only happens when a C# keyword with an @ prefix is included.

Reproduction Steps

private readonly ILogger _logger = new LoggerFactory().CreateLogger("SomeNamespace");

static void Main(string[] args) { }

[LoggerMessage(eventId: 1, LogLevel.Information, "Resource: {resource}. Namespace: {namespace}.")]
partial void LogEvent(string @namespace, string resource);

The above generates the following invalid code (see unescaped variable namespace):

public override string ToString()
{
    var resource = this._resource;
    var namespace = this.@namespace;

    return $"Resource: {resource}. Namespace: {namespace}.";
}

Expected behavior

The generator should generate valid escaped code to reference the c# keywords.

Actual behavior

Some of the warnings and errors include:

Warning	S3251: Supply an implementation for this partial method.
error CS0759: No defining declaration found for implementing declaration of partial method '<invalid-global-code>.LogEvent(string, string)'
error CS0751: A partial method must be declared within a partial type
error CS0116: A namespace cannot directly contain members such as fields, methods or statements
error CS0246: The type or namespace name 'namespace' could not be found (are you missing a using directive or an assembly reference?)
error CS0246: The type or namespace name '__LogEventStruct' could not be found (are you missing a using directive or an assembly reference?)
error CS0540: '<invalid-global-code>.IEnumerable.GetEnumerator()': containing type does not implement interface 'IEnumerable'
error CS0548: '<invalid-global-code>.this[namespace]': property or indexer must have at least one accessor
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IReadOnlyList<KeyValuePair<string, object?>>.this[int]'
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IReadOnlyCollection<KeyValuePair<string, object?>>.Count'
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IEnumerable<KeyValuePair<string, object?>>.GetEnumerator()'
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IEnumerable.GetEnumerator()'

Regression?

No response

Known Workarounds

The order of the placeholders should match the order of the parameters. The following compiles and works fine:

[LoggerMessage(eventId: 1, LogLevel.Information, "Namespace: {namespace}. Resource: {resource}.")]
partial void LogEvent(string @namespace, string resource);

If the placeholder for the C# keyword uses PascalCase as recommended by CA1727, it also works fine:

[LoggerMessage(eventId: 1, LogLevel.Information, "Resource: {resource}. Namespace: {Namespace}.")]
partial void LogEvent(string @namespace, string resource);

Configuration

Reproduced with:

• .NET 7
• Microsoft.Extensions.Logging 7.0.0 and 8.0.0
• Microsoft.Extensions.Logging.Abstractions 7.0.0, 7.0.1 and 8.0.0

Other information

No response

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Issue Details

---

Description

The code below fails to compile depending on the order of the placeholders in the template. It only happens when a C# keyword with an @ prefix is included.

Reproduction Steps

private readonly ILogger _logger = new LoggerFactory().CreateLogger("SomeNamespace");

static void Main(string[] args) { }

[LoggerMessage(eventId: 1, LogLevel.Information, "Resource: {resource}. Namespace: {namespace}.")]
partial void LogEvent(string @namespace, string resource);

The above generates the following invalid code (see unescaped variable namespace):

public override string ToString()
{
    var resource = this._resource;
    var namespace = this.@namespace;

    return $"Resource: {resource}. Namespace: {namespace}.";
}

Expected behavior

The generator should generate valid escaped code to reference the c# keywords.

Actual behavior

Some of the warnings and errors include:

Warning	S3251: Supply an implementation for this partial method.
error CS0759: No defining declaration found for implementing declaration of partial method '<invalid-global-code>.LogEvent(string, string)'
error CS0751: A partial method must be declared within a partial type
error CS0116: A namespace cannot directly contain members such as fields, methods or statements
error CS0246: The type or namespace name 'namespace' could not be found (are you missing a using directive or an assembly reference?)
error CS0246: The type or namespace name '__LogEventStruct' could not be found (are you missing a using directive or an assembly reference?)
error CS0540: '<invalid-global-code>.IEnumerable.GetEnumerator()': containing type does not implement interface 'IEnumerable'
error CS0548: '<invalid-global-code>.this[namespace]': property or indexer must have at least one accessor
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IReadOnlyList<KeyValuePair<string, object?>>.this[int]'
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IReadOnlyCollection<KeyValuePair<string, object?>>.Count'
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IEnumerable<KeyValuePair<string, object?>>.GetEnumerator()'
error CS0535: 'Program.__LogEventStruct' does not implement interface member 'IEnumerable.GetEnumerator()'

Regression?

No response

Known Workarounds

The order of the placeholders should match the order of the parameters. The following compiles and works fine:

[LoggerMessage(eventId: 1, LogLevel.Information, "Namespace: {namespace}. Resource: {resource}.")]
partial void LogEvent(string @namespace, string resource);

If the placeholder for the C# keyword uses PascalCase as recommended by CA1727, it also works fine:

[LoggerMessage(eventId: 1, LogLevel.Information, "Resource: {resource}. Namespace: {Namespace}.")]
partial void LogEvent(string @namespace, string resource);

Configuration

Reproduced with:

• .NET 7
• Microsoft.Extensions.Logging 7.0.0 and 8.0.0
• Microsoft.Extensions.Logging.Abstractions 7.0.0, 7.0.1 and 8.0.0

Other information

No response

Author:	luiscantero
Assignees:	-
Labels:	area-Extensions-Logging
Milestone:	-

[tarekgh]

@luiscantero did you try to prefix the namespace with @ in the message template?

[LoggerMessage(eventId: 1, LogLevel.Information, "Resource: {resource}. Namespace: {@namespace}.")]

The problem is when using template not matching the logger message parameter order, the generator generates a struct to encapsulate the data. The namespace will be a field inside the struct which causes the errors because namespace is a C# keyword. I agree this can be fixed inside the source generator, but it is easy to work around it which makes this issue low priority.

This issue has been marked needs-author-action and may be missing some important information.

[luiscantero]

Hi @tarekgh, using namespace with prefix @ works in the simple case above. But in our actual project it shows SYSLIB1014 and SYSLIB1015: