go-option: library to work with optional types

Pre-generated basic optional types

Gentype Utility

A Go code generator for creating optional types with MessagePack serialization support.

Overview

Gentype generates wrapper types for various Go primitives and custom types that implement optional (some/none) semantics with full MessagePack serialization capabilities. These generated types are useful for representing values that may or may not be present, while ensuring proper encoding and decoding when using MessagePack.

Features

• Generates optional types for built-in types (bool, int, float, string, etc.)
• Supports custom types with MessagePack extension serialization
• Provides common optional type operations:
  • SomeXxx(value) - Create an optional with a value
  • NoneXxx() - Create an empty optional
  • Unwrap(), UnwrapOr(), UnwrapOrElse() - Value extraction
  • IsSome(), IsNone() - Presence checking
• Full MessagePack CustomEncoder and CustomDecoder implementation
• Type-safe operations

Installation

go install github.com/tarantool/go-option/cmd/gentypes@latest
# OR (for go version 1.24+)
go get -tool github.com/tarantool/go-option/cmd/gentypes@latest

Usage

Generating Optional Types

To generate optional types for existing types in a package:

gentypes -package ./path/to/package -ext-code 123
# OR (for go version 1.24+)
go tool gentypes -package ./path/to/package -ext-code 123

Or you can use it to generate file from go:

//go:generate go run github.com/tarantool/go-option/cmd/gentypes@latest -ext-code 123
// OR (for go version 1.24+)
//go:generate go tool gentypes -ext-code 123

Flags:

• -package: Path to the Go package containing types to wrap (default: ".") • -ext-code: MessagePack extension code to use for custom types (must be between -128 and 127, no default value) • -verbose: Enable verbose output (default: false)

Using Generated Types

Generated types follow the pattern Optional and provide methods for working with optional values:

// Create an optional with a value.
opt := SomeOptionalString("hello")

// Check if a value is present.
if opt.IsSome() {
    value := opt.Unwrap()
    fmt.Println(value)
}

// Use a default value if none.
value := opt.UnwrapOr("default")

// Encode to MessagePack.
err := opt.EncodeMsgpack(encoder)