Add FieldLiteral proto message

private/pkg/protosource/option_extension_descriptor.go

@@ -127,15 +127,9 @@ func isDescendantPath(descendant, ancestor []int32) bool {
 	return true
 }
 
-func (o *optionExtensionDescriptor) PresentFields() map[protoreflect.FieldDescriptor]protoreflect.Value {
+func (o *optionExtensionDescriptor) Range(fn func(protoreflect.FieldDescriptor, protoreflect.Value) bool) {
 	// Note: This does not bother to handle unrecognized fields.
 	// Should not be a problem since descriptors models in the buf CLI codebase should have them
 	// all correctly parsed and known.
-	msg := o.message.ProtoReflect()
-	fields := map[protoreflect.FieldDescriptor]protoreflect.Value{}
-	msg.Range(func(fieldDescriptor protoreflect.FieldDescriptor, value protoreflect.Value) bool {
-		fields[fieldDescriptor] = value
-		return true
-	})
-	return fields
+	o.message.ProtoReflect().Range(fn)
 }

private/pkg/protosource/protosource.go

@@ -152,10 +152,9 @@ type OptionExtensionDescriptor interface {
 	// have a set value on this descriptor.
 	PresentExtensionNumbers() []int32
 
-	// PresentFields returns a map of field descriptor to value for all
-	// option fields present. This includes both normal option fields
-	// and extension fields (aka custom options).
-	PresentFields() map[protoreflect.FieldDescriptor]protoreflect.Value
+	// Range implements the same interface as protoreflect.Message. This takes
+	// in a callback that iterates over a protoreflect message field descriptors and values.
+	Range(fn func(protoreflect.FieldDescriptor, protoreflect.Value) bool)
 }
 
 // Location defines source code info location information.