[chore][mdatagen] Use MustNewType for metadata.Type (#31038)

**Description:** 

Follow up to open-telemetry/opentelemetry-collector/pull/9414, adds the
same changes in `mdatagen` regarding validation of `component.Type`s.

On this PR the validation logic and templating is a bit more complex
because of subcomponents. I will add these changes back on core once
this PR is merged.

**Link to tracking Issue:**
open-telemetry/opentelemetry-collector/issues/9208

Author: mx-psi

cmd/mdatagen/internal/metadata/generated_status.go

@@ -328,8 +328,11 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
+var (
+	Type = component.MustNewType("foo")
+)
+
 const (
-	Type             = "foo"
 	MetricsStability = component.StabilityLevelBeta
 )
 
@@ -362,8 +365,11 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
+var (
+	Type = component.MustNewType("foo")
+)
+
 const (
-	Type             = "foo"
 	MetricsStability = component.StabilityLevelAlpha
 )
 

cmd/mdatagen/main_test.go

@@ -8,8 +8,13 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
+{{ if eq .Parent "" }}
+var (
+	Type = component.MustNewType("{{ .Type }}")
+)
+{{- end }}
+
 const (
-	Type = "{{ .Type }}"
 	{{- range $stability, $signals := .Status.Stability }}
 	{{- range $signal := $signals }}
 	{{ toCamelCase $signal }}Stability = component.StabilityLevel{{ casesTitle $stability }}
@@ -23,4 +28,4 @@ func Meter(settings component.TelemetrySettings) metric.Meter {
 
 func Tracer(settings component.TelemetrySettings) trace.Tracer {
 	return settings.TracerProvider.Tracer("{{ .ScopeName }}")
-}
+}

cmd/mdatagen/templates/status.go.tmpl

@@ -6,6 +6,7 @@ package main
 import (
 	"errors"
 	"fmt"
+	"regexp"
 
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.uber.org/multierr"
@@ -28,10 +29,26 @@ func (md *metadata) Validate() error {
 	return errs
 }
 
+// typeRegexp is used to validate the type of a component.
+// A type must start with an ASCII alphabetic character and
+// can only contain ASCII alphanumeric characters and '_'.
+// We allow '/' for subcomponents.
+// This must be kept in sync with the regex in component/config.go.
+var typeRegexp = regexp.MustCompile(`^[a-zA-Z][0-9a-zA-Z_]*$`)
+
 func (md *metadata) validateType() error {
 	if md.Type == "" {
 		return errors.New("missing type")
 	}
+
+	if md.Parent != "" {
+		// subcomponents are allowed to have a '/' in their type.
+		return nil
+	}
+
+	if !typeRegexp.MatchString(md.Type) {
+		return fmt.Errorf("invalid character(s) in type %q", md.Type)
+	}
 	return nil
 }
 

cmd/mdatagen/validate.go

@@ -84,7 +84,7 @@ type serviceGraphConnector struct {
 }
 
 func customMetricName(name string) string {
-	return "connector/" + metadata.Type + "/" + name
+	return "connector/" + metadata.Type.String() + "/" + name
 }
 
 func newConnector(set component.TelemetrySettings, config component.Config) *serviceGraphConnector {