Method getterDefault

protoc-gen-go/generator/generator.go:1693–1732

getterDefault finds the default value for the field to return from a getter, regardless of if it's a built in default or explicit from the source. Returns e.g. "nil", `""`, "Default_MessageType_FieldName"

(field *descriptor.FieldDescriptorProto, goMessageType string)

// getterDefault finds the default value for the field to return from a getter,
// regardless of if it's a built in default or explicit from the source. Returns e.g. "nil", `""`, "Default_MessageType_FieldName"
func (g *Generator) getterDefault(field *descriptor.FieldDescriptorProto, goMessageType string) string {
	if isRepeated(field) {
		return "nil"
	}
	if def := field.GetDefaultValue(); def != "" {
		defaultConstant := g.defaultConstantName(goMessageType, field.GetName())
		if *field.Type != descriptor.FieldDescriptorProto_TYPE_BYTES {
			return defaultConstant
		}
		return "append([]byte(nil), " + defaultConstant + "...)"
	}
	switch *field.Type {
	case descriptor.FieldDescriptorProto_TYPE_BOOL:
		return "false"
	case descriptor.FieldDescriptorProto_TYPE_STRING:
		return `""`
	case descriptor.FieldDescriptorProto_TYPE_GROUP, descriptor.FieldDescriptorProto_TYPE_MESSAGE, descriptor.FieldDescriptorProto_TYPE_BYTES:
		return "nil"
	case descriptor.FieldDescriptorProto_TYPE_ENUM:
		obj := g.ObjectNamed(field.GetTypeName())
		var enum *EnumDescriptor
		if id, ok := obj.(*ImportedDescriptor); ok {
			// The enum type has been publicly imported.
			enum, _ = id.o.(*EnumDescriptor)
		} else {
			enum, _ = obj.(*EnumDescriptor)
		}
		if enum == nil {
			log.Printf("don't know how to generate getter for %s", field.GetName())
			return "nil"
		}
		if len(enum.Value) == 0 {
			return "0 // empty enum"
		}
		first := enum.Value[0].GetName()
		return g.DefaultPackageName(obj) + enum.prefix() + first
	default:
		return "0"
	}
}

// defaultConstantName builds the name of the default constant from the message
// type name and the untouched field name, e.g. "Default_MessageType_FieldName"