go-enumerator

Description

go-enumerator is a code generation tool designed for making constants behave more like enums. The generated methods allow users to:

1. Convert numeric constants to string representations using fmt.Print(x)
2. Parse string representations using fmt.Scan("Name", &x)
3. Check if variables hold valid enum values using x.Defined()
4. Iterate through all defined enum values using x.Next()
5. Marshal and Unmarshal into text/json using x.MarshalText() and x.UmarshalText()

go-enumerator is designed to be invoked by go generate, but it can be used as a command-line tool as well.

Additional documentation available at pkg.go.dev

Installation

Installation is easy, just install the package using the go install tool.

    go install gitlab.com/panicrx/go-enumerator

Overview

Below is an example of the intended use for go-enumerate. All command line arguments are optional go generate. The tool will use the $GOFILE, $GOPACKAGE, and $GOLINE environment variables to find the type declaration immediately following to //go:generate comment.

//go:generate go-enumerator
type Kind int

const (
	Kind1
	Kind2
	Kind3 // DifferentString
)

In this case, we found the Kind type, which is a suitable type for generating an enum definition for. The following methods are created in a new file with the default file name.

// String implements fmt.Stringer
func (sut Kind) String() string { /* omitted for brevity */ }

// Scan implements fmt.Scanner
func (sut *Kind) Scan(ss fmt.ScanState, verb rune) error { /* omitted for brevity */ }

// Defined returns true if sut holds a defined value
func (sut Kind) Defined() bool { /* omitted for brevity */ }

// Next returns the next defined value after sut
func (sut Kind) Next() Kind { /* omitted for brevity */ }

// MarshalText implements encoding.TextMarshaler
func (sut Kind) MarshalText() ([]byte, error) { /* omitted for brevity */ }

// UnmarshalText implements encoding.TextUnmarshaler
func (sut *Kind) UnmarshalText([]byte) error { /* omitted for brevity */ }

String() and Scan() can be used in conjunction with the fmt package to parse and encode values into human-friendly representations.

Next() can be used to loop through all defined values for an enum.

Defined() can be used to ensure that a given variable holds a defined value.

MarshalText and UnmarshalText can be used by themselves, but they are also used by encoding/json and other text-based encoding packages.

Remarks

• go-enumerator was inspired by stringer, which is a better String() generator. If all you need is a String() method for a numeric constant, consider using that tool instead.
• Examples for how to use the generated code can be found at https://pkg.go.dev/gitlab.com/panicrx/go-enumerator/example
• If you find this tool useful, give the repo a star! Feel free leave issues and/or suggest fixes or improvements as well 🙂