Demonstrate compile-time logging source gen without message template

[reyang]

Updating the doc/example to show that it is possible to have structured logging without requiring a message template string.

For users who don't need the format string, this could save computation and networking cost.

[reyang]

These are the warning messages I got:

D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(38,16): warning SYSLIB1015: Argument 'brandNa
me' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/sysl
ib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::TargetFramework
=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(39,16): warning SYSLIB1015: Argument 'product
Description' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnos
tics/syslib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::Target
Framework=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(40,16): warning SYSLIB1015: Argument 'product
Type' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/sy
slib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::TargetFramewo
rk=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(41,16): warning SYSLIB1015: Argument 'recallR
easonDescription' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-di
agnostics/syslib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::T
argetFramework=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(42,16): warning SYSLIB1015: Argument 'company
Name' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/sy
slib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::TargetFramewo
rk=net8.0]

This is probably something that Microsoft.Extensions.Logging would want to consider: either remove the warning entirely if message template is not provided by the user, or provide a single warning message such as "warning SYSLIB1015: logging message is not specified, ..." instead of 5 individual warnings on each key-value pair.

I personally would suggest that we remove the warning message entirely, because this is better aligned with

opentelemetry-dotnet/docs/logs/complex-objects/Program.cs

Lines 34 to 37 in 84bdeb3

	[LoggerMessage(LogLevel.Critical)]
	public static partial void FoodRecallNotice(
	this ILogger logger,
	[LogProperties(OmitReferenceName = true)] FoodRecallNotice foodRecallNotice);

(where we don't get any warning). In addition, many users treat warnings as errors, such warning message might miscommunicate the intention and make the users feel they should always have the message template and pay the cost even if they don't actually benefit from it.

[cijothomas]

this is not intended to be merged, but to open discussion only right?

[reyang]

Using Microsoft.Extenions.Logging.* with a message template:

internal static partial class LoggerExtensions
{
    [LoggerMessage(LogLevel.Critical, "A `{productType}` recall notice was published for `{brandName} {productDescription}` produced by `{companyName}` ({recallReasonDescription}).")]
    public static partial void FoodRecallNotice(
        this ILogger logger,
        string brandName,
        string productDescription,
        string productType,
        string recallReasonDescription,
        string companyName);
}

logger.FoodRecallNotice(
    brandName: "Contoso",
    productDescription: "Salads",
    productType: "Food & Beverages",
    recallReasonDescription: "due to a possible health risk from Listeria monocytogenes",
    companyName: "Contoso Fresh Vegetables, Inc.");

ConsoleLoggerProvider output:

crit: Program[1338249384]
      A `Food & Beverages` recall notice was published for `Contoso Salads` produced by `Contoso Fresh Vegetables, Inc.` (due to a possible health risk from Listeria monocytogenes).

JSON output:

{
    "brandName": "Contoso",
    "productDescription": "Salads",
    "productType": "Food & Beverages",
    "recallReasonDescription": "due to a possible health risk from Listeria monocytogenes",
    "companyName": "Contoso Fresh Vegetables, Inc.",
    "{OriginalFormat}": "A `{productType}` recall notice was published for `{brandName} {productDescription}` produced by `{companyName}` ({recallReasonDescription})."
}

[reyang]

Using Microsoft.Extenions.Logging.* without a message template:

internal static partial class LoggerExtensions
{
    [LoggerMessage(LogLevel.Critical)]
    public static partial void FoodRecallNotice(
        this ILogger logger,
        string brandName,
        string productDescription,
        string productType,
        string recallReasonDescription,
        string companyName);
}

logger.FoodRecallNotice(
    brandName: "Contoso",
    productDescription: "Salads",
    productType: "Food & Beverages",
    recallReasonDescription: "due to a possible health risk from Listeria monocytogenes",
    companyName: "Contoso Fresh Vegetables, Inc.");

ConsoleLoggerProvider output:

crit: Program[1338249384]

JSON output:

{
    "brandName": "Contoso",
    "productDescription": "Salads",
    "productType": "Food & Beverages",
    "recallReasonDescription": "due to a possible health risk from Listeria monocytogenes",
    "companyName": "Contoso Fresh Vegetables, Inc.",
    "{OriginalFormat}": ""
}

Build warnings:

D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(39,16): warning SYSLIB1015: Argument 'brandNa
me' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/sysl
ib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::TargetFramework
=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(40,16): warning SYSLIB1015: Argument 'product
Description' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnos
tics/syslib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::Target
Framework=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(41,16): warning SYSLIB1015: Argument 'product
Type' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/sy
slib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::TargetFramewo
rk=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(42,16): warning SYSLIB1015: Argument 'recallR
easonDescription' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-di
agnostics/syslib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::T
argetFramework=net8.0]
D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\Program.cs(43,16): warning SYSLIB1015: Argument 'company
Name' is not referenced from the logging message (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/sy
slib1015) [D:\repo\opentelemetry-dotnet\docs\logs\getting-started-console\getting-started-console.csproj::TargetFramewo
rk=net8.0]

Summary:

• 5 build warnings that seem misleading/noisy
• ConsoleLoggerProvider output looks weird
• {OriginalFormat} shows up in the generated key-value pairs, the value is empty

[reyang]

Using Microsoft.Extensions.Telemetry.Abstractions without a message template:

var foodRecallNotice = new FoodRecallNotice
{
    BrandName = "Contoso",
    ProductDescription = "Salads",
    ProductType = "Food & Beverages",
    RecallReasonDescription = "due to a possible health risk from Listeria monocytogenes",
    CompanyName = "Contoso Fresh Vegetables, Inc.",
};

logger.FoodRecallNotice(foodRecallNotice);


internal static partial class LoggerExtensions
{
    [LoggerMessage(LogLevel.Critical)]
    public static partial void FoodRecallNotice(
        this ILogger logger,
        [LogProperties(OmitReferenceName = true)] FoodRecallNotice foodRecallNotice);
}

ConsoleLoggerProvider output:

crit: Program[252550133]

JSON output:

{
    "CompanyName": "Contoso Fresh Vegetables, Inc.",
    "RecallReasonDescription": "due to a possible health risk from Listeria monocytogenes",
    "ProductType": "Food & Beverages",
    "ProductDescription": "Salads",
    "BrandName": "Contoso"
}

Summary:

• no build warning
• ConsoleLoggerProvider output looks weird
• no {OriginalFormat} in the generated key-value pairs

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