Add unit parameter to metric source generator

src/Generators/Microsoft.Gen.Metrics/MetricFactoryEmitter.cs

@@ -146,7 +146,15 @@ private void GenMetricFactoryMethods(MetricMethod metricMethod, string nspace)
         OutOpenBrace();
         OutLn($"return {GetMetricDictionaryName(metricMethod)}.GetOrAdd({meterParam.Name}, static _meter =>");
         OutLn("    {");
-        OutLn($"        var instrument = _meter.{createMethodName}(@\"{metricMethod.MetricName}\");");
+        if (string.IsNullOrEmpty(metricMethod.MetricUnit))
+        {
+            OutLn($"        var instrument = _meter.{createMethodName}(@\"{metricMethod.MetricName}\");");
+        }
+        else
+        {
+            OutLn($"        var instrument = _meter.{createMethodName}(@\"{metricMethod.MetricName}\", @\"{metricMethod.MetricUnit}\");");
+        }
+
         OutLn($"        return new {nsprefix}{metricMethod.MetricTypeName}(instrument);");
         OutLn("    });");
         OutCloseBrace();

src/Generators/Microsoft.Gen.Metrics/Model/MetricMethod.cs

@@ -12,6 +12,7 @@ internal sealed class MetricMethod
     public Dictionary<string, string> TagDescriptionDictionary = [];
     public string? Name;
     public string? MetricName;
+    public string? MetricUnit;
     public string? XmlDefinition;
     public bool IsExtensionMethod;
     public string Modifiers = string.Empty;

src/Generators/Microsoft.Gen.Metrics/Parser.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -273,13 +274,14 @@ private static bool TryGetTagNameFromAttribute(ISymbol symbol, SymbolHolder symb
         return false;
     }
 
-    private (string metricName, HashSet<string> tagNames, Dictionary<string, string> dimensionDescriptions) ExtractAttributeParameters(
+    private (string metricName, string metricUnit, HashSet<string> tagNames, Dictionary<string, string> dimensionDescriptions) ExtractAttributeParameters(
         AttributeData attribute,
         SemanticModel semanticModel)
     {
         var tagHashSet = new HashSet<string>();
         var tagDescriptionMap = new Dictionary<string, string>();
         string metricNameFromAttribute = string.Empty;
+        string metricUnitFromAttribute = string.Empty;
         if (!attribute.NamedArguments.IsDefaultOrEmpty)
         {
             foreach (var arg in attribute.NamedArguments)
@@ -288,7 +290,11 @@ private static bool TryGetTagNameFromAttribute(ISymbol symbol, SymbolHolder symb
                     arg.Key is "MetricName" or "Name")
                 {
                     metricNameFromAttribute = (arg.Value.Value ?? string.Empty).ToString().Replace("\\\\", "\\");
-                    break;
+                }
+                else if (arg.Value.Kind == TypedConstantKind.Primitive &&
+                    arg.Key is "Unit")
+                {
+                    metricUnitFromAttribute = (arg.Value.Value ?? string.Empty).ToString();
                 }
             }
         }
@@ -330,7 +336,7 @@ private static bool TryGetTagNameFromAttribute(ISymbol symbol, SymbolHolder symb
             }
         }
 
-        return (metricNameFromAttribute, tagHashSet, tagDescriptionMap);
+        return (metricNameFromAttribute, metricUnitFromAttribute, tagHashSet, tagDescriptionMap);
     }
 
     private string GetSymbolXmlCommentSummary(ISymbol symbol)
@@ -422,20 +428,20 @@ private void GetTagDescription(
         if (!methodAttribute.ConstructorArguments.IsDefaultOrEmpty
             && methodAttribute.ConstructorArguments[0].Kind == TypedConstantKind.Type)
         {
-            KeyValuePair<string, TypedConstant> namedArg = default;
+            ImmutableArray<KeyValuePair<string, TypedConstant>> namedArgs = ImmutableArray<KeyValuePair<string, TypedConstant>>.Empty;
             var ctorArg = methodAttribute.ConstructorArguments[0];
 
             if (!methodAttribute.NamedArguments.IsDefaultOrEmpty)
             {
-                namedArg = methodAttribute.NamedArguments[0];
+                namedArgs = methodAttribute.NamedArguments;
             }
 
-            strongTypeAttrParams = ExtractStrongTypeAttributeParameters(ctorArg, namedArg, symbols);
+            strongTypeAttrParams = ExtractStrongTypeAttributeParameters(ctorArg, namedArgs, symbols);
         }
         else
         {
             var parameters = ExtractAttributeParameters(methodAttribute, semanticModel);
-            (strongTypeAttrParams.MetricNameFromAttribute, strongTypeAttrParams.TagHashSet, strongTypeAttrParams.TagDescriptionDictionary) = parameters;
+            (strongTypeAttrParams.MetricNameFromAttribute, strongTypeAttrParams.MetricUnitFromAttribute, strongTypeAttrParams.TagHashSet, strongTypeAttrParams.TagDescriptionDictionary) = parameters;
         }
 
         string metricNameFromMethod = methodSymbol.ReturnType.Name;
@@ -444,6 +450,7 @@ private void GetTagDescription(
         {
             Name = methodSymbol.Name,
             MetricName = string.IsNullOrWhiteSpace(strongTypeAttrParams.MetricNameFromAttribute) ? metricNameFromMethod : strongTypeAttrParams.MetricNameFromAttribute,
+            MetricUnit = strongTypeAttrParams.MetricUnitFromAttribute,
             InstrumentKind = instrumentKind,
             GenericType = genericType.ToDisplayString(_genericTypeSymbolFormat),
             TagKeys = strongTypeAttrParams.TagHashSet,
@@ -605,14 +612,22 @@ private void Diag(DiagnosticDescriptor desc, Location? location, params object?[
 
     private StrongTypeAttributeParameters ExtractStrongTypeAttributeParameters(
         TypedConstant constructorArg,
-        KeyValuePair<string, TypedConstant> namedArgument,
+        ImmutableArray<KeyValuePair<string, TypedConstant>> namedArguments,
         SymbolHolder symbols)
     {
         var strongTypeAttributeParameters = new StrongTypeAttributeParameters();
 
-        if (namedArgument is { Key: "Name", Value.Value: { } })
+        // Extract "Name" and "Unit" values from the named arguments, if present, and assign them to the corresponding properties.
+        foreach (var namedArgument in namedArguments)
         {
-            strongTypeAttributeParameters.MetricNameFromAttribute = namedArgument.Value.Value.ToString();
+            if (namedArgument.Key == "Name" && namedArgument.Value.Value is { } nameValue)
+            {
+                strongTypeAttributeParameters.MetricNameFromAttribute = nameValue.ToString();
+            }
+            else if (namedArgument.Key == "Unit" && namedArgument.Value.Value is { } unitValue)
+            {
+                strongTypeAttributeParameters.MetricUnitFromAttribute = unitValue.ToString();
+            }
         }
 
         if (constructorArg.IsNull ||

src/Generators/Microsoft.Gen.Metrics/StrongTypeAttributeParameters.cs

@@ -9,6 +9,7 @@ namespace Microsoft.Gen.Metrics;
 internal sealed class StrongTypeAttributeParameters
 {
     public string MetricNameFromAttribute = string.Empty;
+    public string MetricUnitFromAttribute = string.Empty;
     public HashSet<string> TagHashSet = [];
     public Dictionary<string, string> TagDescriptionDictionary = [];
     public List<StrongTypeConfig> StrongTypeConfigs = [];

src/Libraries/Microsoft.Extensions.Telemetry.Abstractions/Metrics/CounterAttribute.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.Shared.DiagnosticIds;
 
 namespace Microsoft.Extensions.Diagnostics.Metrics;
 
@@ -73,7 +75,13 @@ public CounterAttribute(Type type)
     public string[]? TagNames { get; }
 
     /// <summary>
-    /// Gets the type that supplies metric tags values.
+    /// Gets the type that supplies metric tag values.
     /// </summary>
     public Type? Type { get; }
+
+    /// <summary>
+    /// Gets or sets the unit of measurement for the metric.
+    /// </summary>
+    [Experimental(DiagnosticIds.Experiments.Telemetry)]
+    public string? Unit { get; set; }
 }

src/Libraries/Microsoft.Extensions.Telemetry.Abstractions/Metrics/CounterAttributeT.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.Shared.DiagnosticIds;
 
 namespace Microsoft.Extensions.Diagnostics.Metrics;
 
@@ -82,4 +84,10 @@ public CounterAttribute(Type type)
     /// Gets the type that supplies metric tag values.
     /// </summary>
     public Type? Type { get; }
+
+    /// <summary>
+    /// Gets or sets the unit of measurement for the metric.
+    /// </summary>
+    [Experimental(DiagnosticIds.Experiments.Telemetry)]
+    public string? Unit { get; set; }
 }

src/Libraries/Microsoft.Extensions.Telemetry.Abstractions/Metrics/GaugeAttribute.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.Shared.DiagnosticIds;
 
 namespace Microsoft.Extensions.Diagnostics.Metrics;
 
@@ -75,4 +77,10 @@ public GaugeAttribute(Type type)
     /// Gets the type that supplies metric tag values.
     /// </summary>
     public Type? Type { get; }
+
+    /// <summary>
+    /// Gets or sets the unit of measurement for the metric.
+    /// </summary>
+    [Experimental(DiagnosticIds.Experiments.Telemetry)]
+    public string? Unit { get; set; }
 }

src/Libraries/Microsoft.Extensions.Telemetry.Abstractions/Metrics/HistogramAttribute.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.Shared.DiagnosticIds;
 
 namespace Microsoft.Extensions.Diagnostics.Metrics;
 
@@ -75,4 +77,10 @@ public HistogramAttribute(Type type)
     /// Gets the type that supplies metric tag values.
     /// </summary>
     public Type? Type { get; }
+
+    /// <summary>
+    /// Gets or sets the unit of measurement for the metric.
+    /// </summary>
+    [Experimental(DiagnosticIds.Experiments.Telemetry)]
+    public string? Unit { get; set; }
 }

src/Libraries/Microsoft.Extensions.Telemetry.Abstractions/Metrics/HistogramAttributeT.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.Shared.DiagnosticIds;
 
 namespace Microsoft.Extensions.Diagnostics.Metrics;
 
@@ -82,4 +84,10 @@ public HistogramAttribute(Type type)
     /// Gets the type that supplies metric tag values.
     /// </summary>
     public Type? Type { get; }
+
+    /// <summary>
+    /// Gets or sets the unit of measurement for the metric.
+    /// </summary>
+    [Experimental(DiagnosticIds.Experiments.Telemetry)]
+    public string? Unit { get; set; }
 }