[mdatagen] Improve validation for attribute enabled field (#13921)

Resource attributes now require an explicit `enabled` field in
metadata.yaml files, while regular attributes are prohibited from having
this field. This improves validation and prevents configuration errors.

Brought from discussion in
#13900

Fixes
#12722

Author: dmitryax

.chloggen/control-attribute-enabled.yaml

@@ -0,0 +1,27 @@
+# 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. otlpreceiver)
+component: mdatagen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Improve validation for resource attribute `enabled` field in metadata files
+
+# One or more tracking issues or pull requests related to the change
+issues: [12722]
+
+# (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: |
+  Resource attributes now require an explicit `enabled` field in metadata.yaml files, while regular attributes
+  are prohibited from having this field. This improves validation and prevents configuration errors.
+
+# 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: [user]

cmd/mdatagen/internal/loader_test.go

@@ -15,6 +15,10 @@ import (
 	"go.opentelemetry.io/collector/pdata/pmetric"
 )
 
+func boolPtr(b bool) *bool {
+	return &b
+}
+
 func TestTwoPackagesInDirectory(t *testing.T) {
 	contents, err := os.ReadFile("testdata/twopackages.yaml")
 	require.NoError(t, err)
@@ -70,15 +74,15 @@ func TestLoadMetadata(t *testing.T) {
 				ResourceAttributes: map[AttributeName]Attribute{
 					"string.resource.attr": {
 						Description: "Resource attribute with any string value.",
-						Enabled:     true,
+						EnabledPtr:  boolPtr(true),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeStr,
 						},
 						FullName: "string.resource.attr",
 					},
 					"string.enum.resource.attr": {
 						Description: "Resource attribute with a known set of string values.",
-						Enabled:     true,
+						EnabledPtr:  boolPtr(true),
 						Enum:        []string{"one", "two"},
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeStr,
@@ -87,23 +91,23 @@ func TestLoadMetadata(t *testing.T) {
 					},
 					"optional.resource.attr": {
 						Description: "Explicitly disabled ResourceAttribute.",
-						Enabled:     false,
+						EnabledPtr:  boolPtr(false),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeStr,
 						},
 						FullName: "optional.resource.attr",
 					},
 					"slice.resource.attr": {
 						Description: "Resource attribute with a slice value.",
-						Enabled:     true,
+						EnabledPtr:  boolPtr(true),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeSlice,
 						},
 						FullName: "slice.resource.attr",
 					},
 					"map.resource.attr": {
 						Description: "Resource attribute with a map value.",
-						Enabled:     true,
+						EnabledPtr:  boolPtr(true),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeMap,
 						},
@@ -114,7 +118,7 @@ func TestLoadMetadata(t *testing.T) {
 						Warnings: Warnings{
 							IfEnabledNotSet: "This resource_attribute will be disabled by default soon.",
 						},
-						Enabled: true,
+						EnabledPtr: boolPtr(true),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeStr,
 						},
@@ -125,7 +129,7 @@ func TestLoadMetadata(t *testing.T) {
 						Warnings: Warnings{
 							IfConfigured: "This resource_attribute is deprecated and will be removed soon.",
 						},
-						Enabled: false,
+						EnabledPtr: boolPtr(false),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeStr,
 						},
@@ -136,7 +140,7 @@ func TestLoadMetadata(t *testing.T) {
 						Warnings: Warnings{
 							IfEnabled: "This resource_attribute is deprecated and will be removed soon.",
 						},
-						Enabled: true,
+						EnabledPtr: boolPtr(true),
 						Type: ValueType{
 							ValueType: pcommon.ValueTypeStr,
 						},

cmd/mdatagen/internal/metadata.go

@@ -114,6 +114,9 @@ func (md *Metadata) validateResourceAttributes() error {
 		if attr.Type == empty {
 			errs = errors.Join(errs, fmt.Errorf("empty type for resource attribute: %v", name))
 		}
+		if attr.EnabledPtr == nil {
+			errs = errors.Join(errs, fmt.Errorf("enabled field is required for resource attribute: %v", name))
+		}
 	}
 	return errs
 }
@@ -140,6 +143,9 @@ func (md *Metadata) validateAttributes(usedAttrs map[AttributeName]bool) error {
 		if attr.Type == empty {
 			errs = errors.Join(errs, fmt.Errorf("empty type for attribute: %v", attrName))
 		}
+		if attr.EnabledPtr != nil {
+			errs = errors.Join(errs, fmt.Errorf("enabled field is not allowed for regular attribute: %v", attrName))
+		}
 		if !usedAttrs[attrName] {
 			unusedAttrs = append(unusedAttrs, attrName)
 		}
@@ -292,8 +298,8 @@ type Attribute struct {
 	Description string `mapstructure:"description"`
 	// NameOverride can be used to override the attribute name.
 	NameOverride string `mapstructure:"name_override"`
-	// Enabled defines whether the attribute is enabled by default.
-	Enabled bool `mapstructure:"enabled"`
+	// EnabledPtr defines whether the attribute is enabled by default.
+	EnabledPtr *bool `mapstructure:"enabled"`
 	// Include can be used to filter attributes.
 	Include []filter.Config `mapstructure:"include"`
 	// Include can be used to filter attributes.
@@ -310,6 +316,18 @@ type Attribute struct {
 	Optional bool `mapstructure:"optional"`
 }
 
+// Enabled returns the boolean value of EnabledPtr.
+// This method is needed to differentiate between different types of attributes:
+// - Resource attributes: EnabledPtr is always set (non-nil) due to validation
+// - Regular attributes: EnabledPtr is always nil due to validation
+// Panics if EnabledPtr is nil, indicating incorrect template usage.
+func (a Attribute) Enabled() bool {
+	if a.EnabledPtr == nil {
+		panic("Enabled() must not be called on regular attributes, only on resource attributes")
+	}
+	return *a.EnabledPtr
+}
+
 // Name returns actual name of the attribute that is set on the metric after applying NameOverride.
 func (a Attribute) Name() AttributeName {
 	if a.NameOverride != "" {