[mdatagen] Require at least two values for enum attributes

Update validateAttributes and validateResourceAttributes to return a validation error if an enum attribute has fewer than two values. Add unit tests for single-element and empty enum validation.

Author: bhuvan-somisetty

cmd/mdatagen/internal/metadata.go

@@ -178,8 +178,8 @@ func (md *Metadata) validateResourceAttributes() error {
 		if attr.EnabledPtr == nil {
 			errs = errors.Join(errs, fmt.Errorf("enabled field is required for resource attribute: %v", name))
 		}
-		if attr.Enum != nil && len(attr.Enum) == 0 {
-			errs = errors.Join(errs, fmt.Errorf("empty enum for resource attribute: %v", name))
+		if attr.Enum != nil && len(attr.Enum) < 2 {
+			errs = errors.Join(errs, fmt.Errorf("enum for resource attribute %v must have at least two values", name))
 		}
 	}
 	return errs
@@ -319,8 +319,8 @@ func (md *Metadata) validateAttributes(usedAttrs map[AttributeName]bool) error {
 		if attr.EnabledPtr != nil {
 			errs = errors.Join(errs, fmt.Errorf("enabled field is not allowed for regular attribute: %v", attrName))
 		}
-		if attr.Enum != nil && len(attr.Enum) == 0 {
-			errs = errors.Join(errs, fmt.Errorf("empty enum for attribute: %v", attrName))
+		if attr.Enum != nil && len(attr.Enum) < 2 {
+			errs = errors.Join(errs, fmt.Errorf("enum for attribute %v must have at least two values", attrName))
 		}
 		if !usedAttrs[attrName] {
 			unusedAttrs = append(unusedAttrs, attrName)
@@ -733,9 +733,6 @@ func (a Attribute) TestValueTwo() string {
 	if len(a.Enum) > 1 {
 		return fmt.Sprintf(`%q`, a.Enum[1])
 	}
-	if len(a.Enum) == 1 {
-		return fmt.Sprintf(`%q`, a.Enum[0])
-	}
 	switch a.Type.ValueType {
 	case pcommon.ValueTypeEmpty:
 		return ""

cmd/mdatagen/internal/metadata_test.go

@@ -133,11 +133,19 @@ func TestValidate(t *testing.T) {
 		},
 		{
 			name:    "testdata/empty_enum_attr.yaml",
-			wantErr: "empty enum for attribute: string_attr",
+			wantErr: "enum for attribute string_attr must have at least two values",
+		},
+		{
+			name:    "testdata/single_enum_attr.yaml",
+			wantErr: "enum for attribute string_attr must have at least two values",
 		},
 		{
 			name:    "testdata/empty_enum_rattr.yaml",
-			wantErr: "empty enum for resource attribute: string.resource.attr",
+			wantErr: "enum for resource attribute string.resource.attr must have at least two values",
+		},
+		{
+			name:    "testdata/single_enum_rattr.yaml",
+			wantErr: "enum for resource attribute string.resource.attr must have at least two values",
 		},
 		{
 			name:    "testdata/entity_undefined_id_attribute.yaml",
@@ -358,7 +366,7 @@ func TestAttributeTestValueAndTestValueTwo(t *testing.T) {
 				Enum:     []string{"default"},
 			},
 			wantTestVal:  `"default"`,
-			wantTestVal2: `"default"`,
+			wantTestVal2: `"mode-val-2"`,
 		},
 		{
 			name: "empty enum slice",

cmd/mdatagen/internal/testdata/single_enum_attr.yaml

@@ -0,0 +1,24 @@
+type: file
+
+status:
+  class: receiver
+  stability:
+    beta: [metrics]
+
+attributes:
+  string_attr:
+    description: string attribute description
+    type: string
+    enum: ["default"]
+
+metrics:
+  default.metric:
+    enabled: true
+    description: Monotonic cumulative sum int metric enabled by default.
+    stability: development
+    unit: s
+    sum:
+      value_type: int
+      monotonic: true
+      aggregation_temporality: cumulative
+    attributes: [string_attr]

cmd/mdatagen/internal/testdata/single_enum_rattr.yaml

@@ -0,0 +1,13 @@
+type: file
+
+status:
+  class: receiver
+  stability:
+    beta: [metrics]
+
+resource_attributes:
+  string.resource.attr:
+    description: string resource attribute
+    type: string
+    enabled: true
+    enum: ["default"]