Auto Generation of Component Configuration from metadata.yaml

cmd/mdatagen/configgen.go

@@ -0,0 +1,121 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+	"text/template"
+
+	"github.com/atombender/go-jsonschema/pkg/schemas"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/cmd/mdatagen/third_party/gojsonschemagenerator"
+)
+
+const (
+	CONFIG_NAME = "config"
+)
+
+func GenerateConfig(conf any) error {
+	// load config
+	jsonBytes, err := json.Marshal(conf)
+	if err != nil {
+		return fmt.Errorf("failed loading config %w", err)
+	}
+	var schema schemas.Schema
+	if err := json.Unmarshal(jsonBytes, &schema); err != nil {
+		return fmt.Errorf("failed to unmarshal JSON: %w", err)
+	}
+
+	// todo: don't hardcode
+	pkgName := "fileexporter"
+
+	// init generator
+	cfg := gojsonschemagenerator.Config{
+		Warner: func(message string) {
+			logf("Warning: %s", message)
+		},
+		DefaultPackageName:  pkgName,
+		DefaultOutputName:   "config",
+		StructNameFromTitle: true,
+		Tags:                []string{"json", "yaml", "mapstructure"},
+		SchemaMappings:      []gojsonschemagenerator.SchemaMapping{},
+		YAMLPackage:         "gopkg.in/yaml.v3",
+		YAMLExtensions:      []string{".yaml", ".yml"},
+	}
+
+	generator, err := gojsonschemagenerator.New(cfg)
+	if err != nil {
+		return fmt.Errorf("failed to create generator: %w", err)
+	}
+	if err = generator.AddFile(CONFIG_NAME, &schema); err != nil {
+		return fmt.Errorf("failed to add config: %w", err)
+	}
+
+	hasUnsupportedValidations := len(generator.NotSupportedValidations) > 0
+
+	tplVars := struct {
+		ValidatorFuncName string
+	}{
+		ValidatorFuncName: "Validate",
+	}
+	if hasUnsupportedValidations {
+		tplVars.ValidatorFuncName = "ValidateHelper"
+	}
+
+	tpl := `
+func (cfg *Config){{.ValidatorFuncName}}() error {
+	b, err := json.Marshal(cfg)
+	if err != nil {
+			return err
+	}
+	var config Config
+	if err := json.Unmarshal(b, &config); err != nil {
+			return err
+	}
+	return nil
+}`
+	tmpl, err := template.New("validator").Parse(tpl)
+	if err != nil {
+		return fmt.Errorf("failed to parse template: %w", err)
+	}
+
+	for _, source := range generator.Sources() {
+		file, err := os.Create("/tmp/config.go")
+		if err != nil {
+			return fmt.Errorf("failed to create file: %w", err)
+		}
+		defer file.Close()
+
+		buf := bytes.NewBufferString("")
+		if err = tmpl.Execute(buf, tplVars); err != nil {
+			return fmt.Errorf("failed to execute template: %w", err)
+		}
+		// only write custom validation if there are no unsupported validations
+		// source = append(source, []byte(tpl)...)
+		source = append(source, buf.Bytes()...)
+		_, err = file.Write(source)
+
+		if err != nil {
+			return fmt.Errorf("failed writing file: %w", err)
+		}
+	}
+	fmt.Println("done")
+	return nil
+}
+
+func logf(format string, args ...interface{}) {
+	fmt.Fprint(os.Stderr, "go-jsonschema: ")
+	fmt.Fprintf(os.Stderr, format, args...)
+	fmt.Fprint(os.Stderr, "\n")
+}
+
+func dump(v any) {
+	jsonBytes, err := json.Marshal(v)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(string(jsonBytes))
+}

cmd/mdatagen/go.mod

@@ -3,7 +3,10 @@ module github.com/open-telemetry/opentelemetry-collector-contrib/cmd/mdatagen
 go 1.20
 
 require (
+	github.com/atombender/go-jsonschema v0.12.1
 	github.com/google/go-cmp v0.5.9
+	github.com/pkg/errors v0.9.1
+	github.com/sanity-io/litter v1.5.5
 	github.com/stretchr/testify v1.8.4
 	go.opentelemetry.io/collector/component v0.85.0
 	go.opentelemetry.io/collector/confmap v0.85.0
@@ -17,12 +20,17 @@ require (
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/fatih/color v1.13.0 // indirect
+	github.com/goccy/go-yaml v1.11.0 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/knadh/koanf v1.5.0 // indirect
 	github.com/knadh/koanf/v2 v2.0.1 // indirect
+	github.com/mattn/go-colorable v0.1.12 // indirect
+	github.com/mattn/go-isatty v0.0.14 // indirect
 	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/go-wordwrap v1.0.1 // indirect
 	github.com/mitchellh/mapstructure v1.5.1-0.20220423185008-bf980b35cac4 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
@@ -34,8 +42,10 @@ require (
 	go.opentelemetry.io/otel v1.18.0 // indirect
 	go.opentelemetry.io/otel/metric v1.18.0 // indirect
 	go.opentelemetry.io/otel/trace v1.18.0 // indirect
+	golang.org/x/exp v0.0.0-20230711023510-fffb14384f22 // indirect
 	golang.org/x/net v0.15.0 // indirect
 	golang.org/x/sys v0.12.0 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20230711160842-782d3b101e98 // indirect
 	google.golang.org/grpc v1.58.1 // indirect
 	google.golang.org/protobuf v1.31.0 // indirect

cmd/mdatagen/loader.go

@@ -216,6 +216,8 @@ type metadata struct {
 	ScopeName string `mapstructure:"-"`
 	// ShortFolderName is the shortened folder name of the component, removing class if present
 	ShortFolderName string `mapstructure:"-"`
+	// Config is the component configuration.
+	Config any `mapstructure:"config"`
 }
 
 func setAttributesFullName(attrs map[attributeName]attribute) {

cmd/mdatagen/main.go

@@ -26,14 +26,16 @@ const (
 )
 
 func main() {
+	genConfig := flag.Bool("genConfig", false, "generate config files")
 	flag.Parse()
 	yml := flag.Arg(0)
-	if err := run(yml); err != nil {
+	if err := run(yml, *genConfig); err != nil {
 		log.Fatal(err)
 	}
 }
 
-func run(ymlPath string) error {
+func run(ymlPath string, genConfig bool) error {
+
 	if ymlPath == "" {
 		return errors.New("argument must be metadata.yaml file")
 	}
@@ -49,6 +51,18 @@ func run(ymlPath string) error {
 		return fmt.Errorf("failed loading %v: %w", ymlPath, err)
 	}
 
+	// generate configuration
+	if genConfig {
+		if md.Config == nil {
+			return fmt.Errorf("no config found in %v", ymlPath)
+		}
+		err := GenerateConfig(md.Config)
+		if err != nil {
+			return fmt.Errorf("error generating config %w", err)
+		}
+		os.Exit(0)
+	}
+
 	tmplDir := "templates"
 
 	codeDir := filepath.Join(ymlDir, "internal", "metadata")