Add component JSON schema generation to mdatagen

.chloggen/ocb-component-schema-alternative.yaml

@@ -0,0 +1,30 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/otlp)
+component: cmd/mdatagen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add config JSON schema generation
+
+# One or more tracking issues or pull requests related to the change
+issues: [9769]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  The component config JSON schema can be optionally enabled by:
+  ```
+  schema:
+    enabled: true
+  ```
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

cmd/mdatagen/go.mod

@@ -4,10 +4,13 @@ go 1.24.0
 
 require (
 	github.com/google/go-cmp v0.7.0
+	github.com/santhosh-tekuri/jsonschema/v6 v6.0.2
 	github.com/spf13/cobra v1.10.2
 	github.com/stretchr/testify v1.11.1
 	go.opentelemetry.io/collector/component v1.49.0
 	go.opentelemetry.io/collector/component/componenttest v0.143.0
+	go.opentelemetry.io/collector/config/configopaque v1.49.0
+	go.opentelemetry.io/collector/config/configoptional v1.49.0
 	go.opentelemetry.io/collector/confmap v1.49.0
 	go.opentelemetry.io/collector/confmap/provider/fileprovider v1.49.0
 	go.opentelemetry.io/collector/connector v0.143.0
@@ -32,6 +35,7 @@ require (
 	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.1
 	golang.org/x/text v0.32.0
+	golang.org/x/tools v0.40.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
@@ -57,6 +61,7 @@ require (
 	github.com/spf13/pflag v1.0.10 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/collector/component/componentstatus v0.143.0 // indirect
+	go.opentelemetry.io/collector/confmap/xconfmap v0.143.0 // indirect
 	go.opentelemetry.io/collector/connector/xconnector v0.143.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror v0.143.0 // indirect
 	go.opentelemetry.io/collector/consumer/xconsumer v0.143.0 // indirect
@@ -72,6 +77,8 @@ require (
 	go.opentelemetry.io/otel/sdk v1.39.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
+	golang.org/x/mod v0.31.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.39.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251222181119-0a764e51fe1b // indirect
 	google.golang.org/grpc v1.78.0 // indirect

cmd/mdatagen/internal/command.go

@@ -22,6 +22,8 @@ import (
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
 	"gopkg.in/yaml.v3"
+
+	"go.opentelemetry.io/collector/cmd/mdatagen/internal/schemagen"
 )
 
 const (
@@ -216,6 +218,11 @@ func run(ymlPath string) error {
 		}
 	}
 
+	// Generate JSON schema if enabled
+	if err := generateSchema(md, ymlDir); err != nil {
+		return fmt.Errorf("failed to generate schema: %w", err)
+	}
+
 	return nil
 }
 
@@ -492,3 +499,60 @@ func validateYAMLKeyOrder(raw []byte) error {
 	}
 	return nil
 }
+
+// generateSchema generates a JSON schema for the component's config if enabled.
+func generateSchema(md Metadata, ymlDir string) error {
+	// Skip if schema generation is not enabled
+	if md.Schema == nil || !md.Schema.Enabled {
+		return nil
+	}
+
+	// Skip non-component types
+	if md.Status == nil || slices.Contains(nonComponents, md.Status.Class) {
+		return nil
+	}
+
+	// Create schemas directory
+	outputDir := filepath.Join(ymlDir, "internal", md.GeneratedPackageName, "schemas")
+	if err := os.MkdirAll(outputDir, 0o700); err != nil {
+		return fmt.Errorf("failed to create schemas directory: %w", err)
+	}
+
+	// Parse config type specification
+	pkgPath, typeName := parseConfigType(md.Schema.ConfigType)
+
+	// Create analyzer and generator
+	analyzer := schemagen.NewPackageAnalyzer(ymlDir)
+	generator := schemagen.NewSchemaGenerator(outputDir, analyzer)
+
+	// Generate schema
+	return generator.GenerateSchema(md.Status.Class, md.Type, typeName, pkgPath)
+}
+
+// parseConfigType parses a config type specification into package path and type name.
+// Examples:
+//   - "Config" -> ("", "Config")
+//   - "go.opentelemetry.io/collector/pkg.Config" -> ("go.opentelemetry.io/collector/pkg", "Config")
+func parseConfigType(configType string) (pkgPath, typeName string) {
+	if configType == "" {
+		return "", ""
+	}
+
+	// Find the last dot that separates package path from type name
+	lastDot := strings.LastIndex(configType, ".")
+	if lastDot == -1 {
+		// No dot means it's just a type name in the local package
+		return "", configType
+	}
+
+	// Check if this looks like a package path (contains "/" before the last dot)
+	potentialPkg := configType[:lastDot]
+	if strings.Contains(potentialPkg, "/") {
+		// It's a fully qualified type: pkg/path.TypeName
+		return potentialPkg, configType[lastDot+1:]
+	}
+
+	// No slash means it's just a type name (e.g., "Config" or possibly "pkg.Config" for local)
+	// Treat as local type name
+	return "", configType
+}

cmd/mdatagen/internal/command_test.go

@@ -820,3 +820,40 @@ func Tracer(settings component.TelemetrySettings) trace.Tracer {
 		})
 	}
 }
+
+func TestGenerateSchema_Skipped(t *testing.T) {
+	tests := []struct {
+		name string
+		md   Metadata
+	}{
+		{
+			name: "schema is nil",
+			md: Metadata{
+				Type:   "test",
+				Status: &Status{Class: "exporter"},
+			},
+		},
+		{
+			name: "explicitly disabled",
+			md: Metadata{
+				Type:   "test",
+				Status: &Status{Class: "exporter"},
+				Schema: &SchemaConfig{Enabled: false},
+			},
+		},
+		{
+			name: "non-component type",
+			md: Metadata{
+				Type:   "test",
+				Status: &Status{Class: "cmd"},
+				Schema: &SchemaConfig{Enabled: true},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := generateSchema(tt.md, t.TempDir())
+			require.NoError(t, err)
+		})
+	}
+}

cmd/mdatagen/internal/loader_test.go

@@ -52,6 +52,9 @@ func TestLoadMetadata(t *testing.T) {
 				SemConvVersion:       "1.38.0",
 				PackageName:          "go.opentelemetry.io/collector/cmd/mdatagen/internal/samplereceiver",
 				ReaggregationEnabled: true,
+				Schema: &SchemaConfig{
+					Enabled: true,
+				},
 				Status: &Status{
 					DisableCodeCov: true,
 					Class:          "receiver",

cmd/mdatagen/internal/metadata.go

@@ -54,6 +54,8 @@ type Metadata struct {
 	Tests Tests `mapstructure:"tests"`
 	// PackageName is the name of the package where the component is defined.
 	PackageName string `mapstructure:"package_name"`
+	// Schema holds configuration for JSON schema generation.
+	Schema *SchemaConfig `mapstructure:"schema"`
 }
 
 func (md Metadata) GetCodeCovComponentID() string {

cmd/mdatagen/internal/samplereceiver/config.go

@@ -0,0 +1,108 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package samplereceiver // import "go.opentelemetry.io/collector/cmd/mdatagen/internal/samplereceiver"
+
+import (
+	"time"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/configopaque"
+	"go.opentelemetry.io/collector/config/configoptional"
+)
+
+var _ component.Factory = (*AnotherStruct)(nil)
+
+type AnotherStruct struct{}
+
+func (a AnotherStruct) Type() component.Type {
+	// TODO implement me
+	panic("implement me")
+}
+
+func (a AnotherStruct) CreateDefaultConfig() component.Config {
+	// TODO implement me
+	panic("implement me")
+}
+
+var _ component.Config = (*MyConfig)(nil)
+
+type CustomString string
+
+// NetworkConfig holds network configuration that should be squashed into parent.
+type NetworkConfig struct {
+	// Host is the network host.
+	Host string `mapstructure:"host"`
+
+	// Port is the network port.
+	Port int `mapstructure:"port"`
+}
+
+// MyConfig defines configuration for the sample exporter used to test schema generation.
+type MyConfig struct {
+	// Network is squashed into the parent config.
+	Network NetworkConfig `mapstructure:",squash"`
+
+	// ID is the component identifier.
+	ID component.ID `mapstructure:"id"`
+
+	// Endpoint is the target URL to send data to.
+	Endpoint string `mapstructure:"endpoint"`
+
+	// CustomString is a custom string.
+	CustomString CustomString `mapstructure:"custom_string"`
+
+	// Timeout is the maximum time to wait for a response.
+	Timeout time.Duration `mapstructure:"timeout"`
+
+	// StartTime is the time when the receiver should start collecting data.
+	StartTime time.Time `mapstructure:"start_time"`
+
+	// Enabled controls whether the exporter is active.
+	Enabled bool `mapstructure:"enabled"`
+
+	// BatchSize is the number of items to send in each batch.
+	BatchSize int `mapstructure:"batch_size"`
+
+	// Headers are additional headers to include in requests.
+	Headers map[string]string `mapstructure:"headers"`
+
+	// Retry contains retry configuration.
+	Retry RetryConfig `mapstructure:"retry"`
+
+	// Tags are optional tags to attach.
+	Tags []string `mapstructure:"tags"`
+
+	// APIKey is a secret API key (opaque string).
+	APIKey configopaque.String `mapstructure:"api_key"`
+
+	// OptionalRetry is an optional retry configuration.
+	OptionalRetry configoptional.Optional[RetryConfig] `mapstructure:"optional_retry"`
+
+	// Secrets is a list of secret key-value pairs.
+	Secrets configopaque.MapList `mapstructure:"secrets"`
+
+	// Endpoints is a list of endpoint configurations.
+	Endpoints []EndpointConfig `mapstructure:"endpoints"`
+
+	// InternalState is an internal field that should be excluded from the schema.
+	InternalState string `mapstructure:"-"`
+}
+
+// EndpointConfig holds configuration for a single endpoint.
+type EndpointConfig struct {
+	// URL is the endpoint URL.
+	URL string `mapstructure:"url"`
+
+	// Priority is the endpoint priority.
+	Priority int `mapstructure:"priority"`
+}
+
+// RetryConfig holds retry settings.
+type RetryConfig struct {
+	// MaxRetries is the maximum number of retries.
+	MaxRetries int `mapstructure:"max_retries"`
+
+	// InitialInterval is the initial retry interval.
+	InitialInterval time.Duration `mapstructure:"initial_interval"`
+}

cmd/mdatagen/internal/samplereceiver/factory.go

@@ -18,7 +18,7 @@ import (
 func NewFactory() receiver.Factory {
 	return receiver.NewFactory(
 		metadata.Type,
-		func() component.Config { return &struct{}{} },
+		func() component.Config { return &MyConfig{} },
 		receiver.WithTraces(createTraces, metadata.TracesStability),
 		receiver.WithMetrics(createMetrics, metadata.MetricsStability),
 		receiver.WithLogs(createLogs, metadata.LogsStability))