feat(requires): support variable references in enum constraints (#2678)

taskfile/ast/requires.go

@@ -22,9 +22,56 @@ func (r *Requires) DeepCopy() *Requires {
 	}
 }
 
+// Enum represents an enum constraint for a required variable.
+// It can either be a static list of values or a reference to another variable.
+type Enum struct {
+	Ref   string
+	Value []string
+}
+
+func (e *Enum) DeepCopy() *Enum {
+	if e == nil {
+		return nil
+	}
+	return &Enum{
+		Ref:   e.Ref,
+		Value: deepcopy.Slice(e.Value),
+	}
+}
+
+// UnmarshalYAML implements yaml.Unmarshaler interface.
+func (e *Enum) UnmarshalYAML(node *yaml.Node) error {
+	switch node.Kind {
+	case yaml.SequenceNode:
+		// Static list of values: enum: ["a", "b"]
+		var values []string
+		if err := node.Decode(&values); err != nil {
+			return errors.NewTaskfileDecodeError(err, node)
+		}
+		e.Value = values
+		return nil
+
+	case yaml.MappingNode:
+		// Reference to another variable: enum: { ref: .VAR }
+		var refStruct struct {
+			Ref string
+		}
+		if err := node.Decode(&refStruct); err != nil {
+			return errors.NewTaskfileDecodeError(err, node)
+		}
+		if refStruct.Ref == "" {
+			return errors.NewTaskfileDecodeError(nil, node).WithTypeMessage("enum")
+		}
+		e.Ref = refStruct.Ref
+		return nil
+	}
+
+	return errors.NewTaskfileDecodeError(nil, node).WithTypeMessage("enum")
+}
+
 type VarsWithValidation struct {
 	Name string
-	Enum []string
+	Enum *Enum
 }
 
 func (v *VarsWithValidation) DeepCopy() *VarsWithValidation {
@@ -33,7 +80,7 @@ func (v *VarsWithValidation) DeepCopy() *VarsWithValidation {
 	}
 	return &VarsWithValidation{
 		Name: v.Name,
-		Enum: v.Enum,
+		Enum: v.Enum.DeepCopy(),
 	}
 }
 
@@ -53,7 +100,7 @@ func (v *VarsWithValidation) UnmarshalYAML(node *yaml.Node) error {
 	case yaml.MappingNode:
 		var vv struct {
 			Name string
-			Enum []string
+			Enum *Enum
 		}
 		if err := node.Decode(&vv); err != nil {
 			return errors.NewTaskfileDecodeError(err, node)