[Metric builder] Replace enum attributes values with typed constants (o…

…pen-telemetry#9683)

`Record...DataPoint` functions should take one of predefined attribute values instead of any string if the attribute has enum field defined in metadata.yaml. This significantly reduces chance of passing wrong attribute values and helps to ensure accuracy of the automatically generated documentation.

CHANGELOG.md

@@ -17,6 +17,7 @@
 
 ### 💡 Enhancements 💡
 
+- `cmd/mdatagen`: Replace enum attributes values with typed constants (#9683)
 - `k8sclusterreceiver`: Validate that k8s API supports a resource before setting up a watcher for it (#9523)
 - `internal/stanza`: Add support for `remove` operator (#9524)
 - `k8sattributesprocessor`: Support regex capture groups in tag_name (#9525)

cmd/mdatagen/main.go

@@ -86,6 +86,9 @@ func generateMetrics(ymlDir string, thisDir string, md metadata, useExpGen bool)
 				"publicVar": func(s string) (string, error) {
 					return formatIdentifier(s, true)
 				},
+				"attributeInfo": func(an attributeName) attribute {
+					return md.Attributes[an]
+				},
 				"parseImportsRequired": func(metrics map[metricName]metric) bool {
 					for _, m := range metrics {
 						if m.Data().HasMetricInputType() {

cmd/mdatagen/metrics_v2.tmpl

@@ -38,6 +38,39 @@ func DefaultMetricsSettings() MetricsSettings {
 	}
 }
 
+{{ range $name, $info := .Attributes }}
+{{- if $info.Enum -}}
+// Attribute{{ $name.Render }} specifies the a value {{ $name }} attribute.
+type Attribute{{ $name.Render }} int
+
+const (
+	_ Attribute{{ $name.Render }} = iota
+	{{- range $info.Enum }}
+	Attribute{{ $name.Render }}{{ . | publicVar }}
+	{{- end }}
+)
+
+// String returns the string representation of the Attribute{{ $name.Render }}.
+func (av Attribute{{ $name.Render }}) String() string {
+	switch av {
+	{{- range $info.Enum }}
+	case Attribute{{ $name.Render }}{{ . | publicVar }}:
+		return "{{ . }}"
+	{{- end }}
+	}
+	return ""
+}
+
+// MapAttribute{{ $name.Render }} is a helper map of string to Attribute{{ $name.Render }} attribute value.
+var MapAttribute{{ $name.Render }} = map[string]Attribute{{ $name.Render }}{
+	{{- range $info.Enum }}
+	"{{ . }}": Attribute{{ $name.Render }}{{ . | publicVar }},
+	{{- end }}
+}
+
+{{ end }}
+{{- end }}
+
 {{ range $name, $metric := .Metrics -}}
 type metric{{ $name.Render }} struct {
 	data     pmetric.Metric   // data buffer for generated metric.
@@ -206,7 +239,9 @@ func (mb *MetricsBuilder) Record{{ $name.Render }}DataPoint(ts pcommon.Timestamp
 	{{- else }}
 	{{- if $metric.Data.HasMetricValueType }}, val {{ $metric.Data.MetricValueType.BasicType }}{{- end }}
 	{{- end -}}
-	{{- range $metric.Attributes -}} , {{ .RenderUnexported }}AttributeValue string{{ end }})
+	{{- range $metric.Attributes -}}
+	, {{ .RenderUnexported }}AttributeValue {{ if (attributeInfo .).Enum }}Attribute{{ .Render }}{{ else }}string{{ end }}
+	{{- end }})
 	{{- if $metric.Data.HasMetricInputType }} error{{ end }} {
 	{{- if $metric.Data.HasMetricInputType }}
 	{{- if $metric.Data.HasMetricValueType }}
@@ -225,15 +260,19 @@ func (mb *MetricsBuilder) Record{{ $name.Render }}DataPoint(ts pcommon.Timestamp
 	} else {
 		mb.metric{{ $name.Render }}.recordDataPoint(mb.startTime, ts
 		{{- if $metric.Data.HasMetricValueType }}, i {{ end }}
-		{{- range $metric.Attributes -}} , {{ .RenderUnexported }}AttributeValue{{ end }})
+		{{- range $metric.Attributes -}}
+		, {{ .RenderUnexported }}AttributeValue{{ if (attributeInfo .).Enum }}.String(){{ end }}
+		{{- end }})
 	}
 	{{- end }}
 	return nil
 	{{- end }}
 	{{- else }}
 	mb.metric{{ $name.Render }}.recordDataPoint(mb.startTime, ts
 		{{- if $metric.Data.HasMetricValueType }}, val {{ end }}
-		{{- range $metric.Attributes -}} , {{ .RenderUnexported }}AttributeValue{{ end }})
+		{{- range $metric.Attributes -}}
+		, {{ .RenderUnexported }}AttributeValue{{ if (attributeInfo .).Enum }}.String(){{ end }}
+		{{- end }})
 	{{- end }}
 }
 {{ end }}
@@ -265,18 +304,3 @@ var Attributes = struct {
 
 // A is an alias for Attributes.
 var A = Attributes
-
-{{ range $name, $info := .Attributes -}}
-{{ if $info.Enum -}}
-// Attribute{{ $name.Render }} are the possible values that the attribute "{{ $name }}" can have.
-var Attribute{{ $name.Render }} = struct {
-{{- range $info.Enum }}
-	{{ . | publicVar }} string
-{{- end }}
-}{
-{{- range $info.Enum }}
-	"{{ . }}",
-{{- end }}
-}
-{{ end }}
-{{ end }}