[cmd/mdatagen] Remove the old metadata generator (open-telemetry#13374)

All receivers were migrated to the new metrics builder. We can remove the old mdatagen tool and declare the new metrics builder as stable.

cmd/mdatagen/documentation.tmpl

@@ -14,15 +14,14 @@ These are the metrics available for this scraper.
 {{- range $index, $attributeName := $metricInfo.Attributes }} <li>{{ $attributeName }}</li> {{- end }} </ul> |
 {{- end }}
 
-**Highlighted metrics** are emitted by default.{{ if .ExpGen }} Other metrics are optional and not emitted by default.
+**Highlighted metrics** are emitted by default. Other metrics are optional and not emitted by default.
 Any metric can be enabled or disabled with the following scraper configuration:
 
 ```yaml
 metrics:
   <metric_name>:
     enabled: <true|false>
 ```
-{{- end }}
 
 {{- if .ResourceAttributes }}
 

cmd/mdatagen/loader.go

@@ -166,9 +166,6 @@ type templateContext struct {
 	metadata
 	// Package name for generated code.
 	Package string
-	// ExpGen identifies whether the experimental metrics generator is used.
-	// TODO: Remove once the old mdata generator is gone.
-	ExpGen bool
 }
 
 func loadMetadata(filePath string) (metadata, error) {

cmd/mdatagen/main.go

@@ -29,22 +29,19 @@ import (
 )
 
 const (
-	tmplFileV1   = "metrics.tmpl"
-	outputFileV1 = "generated_metrics.go"
-	tmplFileV2   = "metrics_v2.tmpl"
-	outputFileV2 = "generated_metrics_v2.go"
+	tmplFile   = "metrics.tmpl"
+	outputFile = "generated_metrics.go"
 )
 
 func main() {
-	useExpGen := flag.Bool("experimental-gen", false, "Use experimental generator")
 	flag.Parse()
 	yml := flag.Arg(0)
-	if err := run(yml, *useExpGen); err != nil {
+	if err := run(yml); err != nil {
 		log.Fatal(err)
 	}
 }
 
-func run(ymlPath string, useExpGen bool) error {
+func run(ymlPath string) error {
 	if ymlPath == "" {
 		return errors.New("argument must be metadata.yaml file")
 	}
@@ -62,20 +59,13 @@ func run(ymlPath string, useExpGen bool) error {
 	}
 	thisDir := filepath.Dir(filename)
 
-	if err = generateMetrics(ymlDir, thisDir, md, useExpGen); err != nil {
+	if err = generateMetrics(ymlDir, thisDir, md); err != nil {
 		return err
 	}
-	return generateDocumentation(ymlDir, thisDir, md, useExpGen)
+	return generateDocumentation(ymlDir, thisDir, md)
 }
 
-func generateMetrics(ymlDir string, thisDir string, md metadata, useExpGen bool) error {
-	tmplFile := tmplFileV1
-	outputFile := outputFileV1
-	if useExpGen {
-		tmplFile = tmplFileV2
-		outputFile = outputFileV2
-	}
-
+func generateMetrics(ymlDir string, thisDir string, md metadata) error {
 	tmpl := template.Must(
 		template.
 			New(tmplFile).
@@ -123,20 +113,18 @@ func generateMetrics(ymlDir string, thisDir string, md metadata, useExpGen bool)
 	if err := os.MkdirAll(outputDir, 0700); err != nil {
 		return fmt.Errorf("unable to create output directory %q: %w", outputDir, err)
 	}
-	for _, f := range []string{filepath.Join(outputDir, outputFileV1), filepath.Join(outputDir, outputFileV2)} {
-		if err := os.Remove(f); err != nil && !errors.Is(err, os.ErrNotExist) {
-			return fmt.Errorf("unable to remove genererated file %q: %w", f, err)
-		}
-	}
 	outputFilepath := filepath.Join(outputDir, outputFile)
+	if err := os.Remove(outputFilepath); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("unable to remove genererated file %q: %w", outputFilepath, err)
+	}
 	if err := os.WriteFile(outputFilepath, formatted, 0600); err != nil {
 		return fmt.Errorf("failed writing %q: %w", outputFilepath, err)
 	}
 
 	return nil
 }
 
-func generateDocumentation(ymlDir string, thisDir string, md metadata, useExpGen bool) error {
+func generateDocumentation(ymlDir string, thisDir string, md metadata) error {
 	tmpl := template.Must(
 		template.
 			New("documentation.tmpl").
@@ -150,7 +138,7 @@ func generateDocumentation(ymlDir string, thisDir string, md metadata, useExpGen
 
 	buf := bytes.Buffer{}
 
-	tmplCtx := templateContext{metadata: md, ExpGen: useExpGen, Package: "metadata"}
+	tmplCtx := templateContext{metadata: md, Package: "metadata"}
 	if err := tmpl.Execute(&buf, tmplCtx); err != nil {
 		return fmt.Errorf("failed executing template: %w", err)
 	}

cmd/mdatagen/main_test.go

@@ -50,8 +50,7 @@ metrics:
 
 func Test_runContents(t *testing.T) {
 	type args struct {
-		yml       string
-		useExpGen bool
+		yml string
 	}
 	tests := []struct {
 		name                  string
@@ -62,19 +61,13 @@ func Test_runContents(t *testing.T) {
 	}{
 		{
 			name:                  "valid metadata",
-			args:                  args{validMetadata, false},
-			expectedDocumentation: "testdata/documentation_v1.md",
-			want:                  "",
-		},
-		{
-			name:                  "valid metadata v2",
-			args:                  args{validMetadata, true},
-			expectedDocumentation: "testdata/documentation_v2.md",
+			args:                  args{validMetadata},
+			expectedDocumentation: "testdata/documentation.md",
 			want:                  "",
 		},
 		{
 			name:    "invalid yaml",
-			args:    args{"invalid", false},
+			args:    args{"invalid"},
 			want:    "",
 			wantErr: true,
 		},
@@ -86,18 +79,14 @@ func Test_runContents(t *testing.T) {
 			metadataFile := filepath.Join(tmpdir, "metadata.yaml")
 			require.NoError(t, os.WriteFile(metadataFile, []byte(tt.args.yml), 0600))
 
-			err := run(metadataFile, tt.args.useExpGen)
+			err := run(metadataFile)
 			if tt.wantErr {
 				require.Error(t, err)
 				return
 			}
 			require.NoError(t, err)
 
-			genFilePath := filepath.Join(tmpdir, "internal/metadata/generated_metrics.go")
-			if tt.args.useExpGen {
-				genFilePath = filepath.Join(tmpdir, "internal/metadata/generated_metrics_v2.go")
-			}
-			require.FileExists(t, genFilePath)
+			require.FileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_metrics.go"))
 
 			actualDocumentation := filepath.Join(tmpdir, "documentation.md")
 			require.FileExists(t, actualDocumentation)
@@ -136,7 +125,7 @@ func Test_run(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if err := run(tt.args.ymlPath, false); (err != nil) != tt.wantErr {
+			if err := run(tt.args.ymlPath); (err != nil) != tt.wantErr {
 				t.Errorf("run() error = %v, wantErr %v", err, tt.wantErr)
 			}
 		})

cmd/mdatagen/metric-metadata.yaml

@@ -31,7 +31,7 @@ attributes:
 # being described below.
 metrics:
   <metric.name>:
-    # Required: whether the metric is collected by default. Takes effect only with "--experimental-gen" mdatagen flag.
+    # Required: whether the metric is collected by default.
     enabled: # true | false
     # Required: metric description.
     description: