goenums is a tool to help you generate go type safe enums that are much more tightly typed than just iota defined enums.
go install github.com/zarldev/goenums@latest
$ goenums -h
____ _____ ___ ____ __ ______ ___ _____
/ __ '/ __ \/ _ \/ __ \/ / / / __ '__ \/ ___/
/ /_/ / /_/ / __/ / / / /_/ / / / / / (__ )
\__, /\____/\___/_/ /_/\__,_/_/ /_/ /_/____/
/____/
Usage: goenums [options] filename
Options:
-f
-failfast
Enable failfast mode - fail on generation of invalid enum while parsing (default: false)
-h
-help
Print help information
-v
-version
Print version information
Defining the list of enums in the respective go file and then point the goenum binary at the require file. This can be specified in the go generate command like below: For example we have the file below called status.go :
package validation
type status int
//go:generate goenums status.go
const (
unknown status = iota // invalid
failed
passed
skipped
scheduled
running
booked
)Now running the go generate command will generate the following code in a new file called statuses_enums.go
// Code generated by goenums. DO NOT EDIT.
// This file was generated by github.com/zarldev/goenums
// using the command:
// goenums status.go
package validation
import (
"bytes"
"database/sql/driver"
"fmt"
"strconv"
)
type Status struct {
status
}
type statusesContainer struct {
UNKNOWN Status
FAILED Status
PASSED Status
SKIPPED Status
SCHEDULED Status
RUNNING Status
BOOKED Status
}
var Statuses = statusesContainer{
FAILED: Status{
status: failed,
},
PASSED: Status{
status: passed,
},
SKIPPED: Status{
status: skipped,
},
SCHEDULED: Status{
status: scheduled,
},
RUNNING: Status{
status: running,
},
BOOKED: Status{
status: booked,
},
}
func (c statusesContainer) All() []Status {
return []Status{
c.FAILED,
c.PASSED,
c.SKIPPED,
c.SCHEDULED,
c.RUNNING,
c.BOOKED,
}
}
var invalidStatus = Status{}
func ParseStatus(a any) (Status, error) {
res := invalidStatus
switch v := a.(type) {
case Status:
return v, nil
case []byte:
res = stringToStatus(string(v))
case string:
res = stringToStatus(v)
case fmt.Stringer:
res = stringToStatus(v.String())
case int:
res = intToStatus(v)
case int64:
res = intToStatus(int(v))
case int32:
res = intToStatus(int(v))
}
return res, nil
}
func stringToStatus(s string) Status {
switch s {
case "unknown":
return Statuses.UNKNOWN
case "failed":
return Statuses.FAILED
case "passed":
return Statuses.PASSED
case "skipped":
return Statuses.SKIPPED
case "scheduled":
return Statuses.SCHEDULED
case "running":
return Statuses.RUNNING
case "booked":
return Statuses.BOOKED
}
return invalidStatus
}
func intToStatus(i int) Status {
if i < 0 || i >= len(Statuses.All()) {
return invalidStatus
}
return Statuses.All()[i]
}
func ExhaustiveStatuss(f func(Status)) {
for _, p := range Statuses.All() {
f(p)
}
}
var validStatuses = map[Status]bool{
Statuses.FAILED: true,
Statuses.PASSED: true,
Statuses.SKIPPED: true,
Statuses.SCHEDULED: true,
Statuses.RUNNING: true,
Statuses.BOOKED: true,
}
func (p Status) IsValid() bool {
return validStatuses[p]
}
func (p Status) MarshalJSON() ([]byte, error) {
return []byte(`"` + p.String() + `"`), nil
}
func (p *Status) UnmarshalJSON(b []byte) error {
b = bytes.Trim(bytes.Trim(b, `"`), ` `)
newp, err := ParseStatus(b)
if err != nil {
return err
}
*p = newp
return nil
}
func (p *Status) Scan(value any) error {
newp, err := ParseStatus(value)
if err != nil {
return err
}
*p = newp
return nil
}
func (p Status) Value() (driver.Value, error) {
return p.String(), nil
}
func _() {
// An "invalid array index" compiler error signifies that the constant values have changed.
// Re-run the goenums command to generate them again.
// Does not identify newly added constant values unless order changes
var x [1]struct{}
_ = x[unknown-0]
_ = x[failed-1]
_ = x[passed-2]
_ = x[skipped-3]
_ = x[scheduled-4]
_ = x[running-5]
_ = x[booked-6]
}
const _statuses_name = "unknownfailedpassedskippedscheduledrunningbooked"
var _statuses_index = [...]uint16{0, 7, 13, 19, 26, 35, 42, 48}
func (i status) String() string {
if i < 0 || i >= status(len(_statuses_index)-1) {
return "statuses(" + (strconv.FormatInt(int64(i), 10) + ")")
}
return _statuses_name[_statuses_index[i]:_statuses_index[i+1]]
}All enums are generated with a String representation for each enum and JSON Marshaling and UnMarshaling for use in HTTP Request structs. The string function is now the same as the go cmd stringer for the base case.
The generated enum type also implements the JSON.UnMarshal, JSON.Marshal interfaces along with the sql.Scanner and sql.Valuer interface to handle parsing over the wire via HTTP or a Database.
You can enable the generator to adjust the JSONUnmarshal method so that it will return an error if an enum is found to be invalid.
This is triggered by the failfast flag -f or -failfast.
Here is the updated ParseXXX function for the Status example where we have enabled failfast in the go generate command.
//go:generate goenums -f status.go
type status int
func ParseStatus(a any) (Status, error) {
res := invalidStatus
switch v := a.(type) {
case Status:
return v, nil
case []byte:
res = stringToStatus(string(v))
case string:
res = stringToStatus(v)
case fmt.Stringer:
res = stringToStatus(v.String())
case int:
res = intToStatus(v)
case int64:
res = intToStatus(int(v))
case int32:
res = intToStatus(int(v))
}
if res == invalidStatus {
return res, fmt.Errorf("failed to parse %v", a)
}
return res, nil
}The enums can have additional functionality added by just adding comments to the type definition and corresponding values to the comments in the iota definitions. There is also the invalid comment flag which will no longer include the value in the exhaustive list.
Extensions via comments is a comma separated list of Name and Type declarations, these declarations can be done in 1 of 3 formats depending on preference.
- Spaces
Gravity float64,RadiusKm float64,MassKg float64,OrbitKm float64 - Square Brackets
Gravity[float64],RadiusKm[float64],MassKg[float64],OrbitKm[float64] - Parenthesis
Gravity(float64),RadiusKm(float64),MassKg(float64),OrbitKm(float64)
For example we have the file below called planets.go :
package solarsystem
type planet int // Gravity[float64],RadiusKm[float64],MassKg[float64],OrbitKm[float64],OrbitDays[float64],SurfacePressureBars[float64],Moons[int],Rings[bool]
//go:generate goenums planets.go
const (
unknown planet = iota // invalid
mercury // Mercury 0.378,2439.7,3.3e23,57910000,88,0.0000000001,0,false
venus // Venus 0.907,6051.8,4.87e24,108200000,225,92,0,false
earth // Earth 1,6378.1,5.97e24,149600000,365,1,1,false
mars // Mars 0.377,3389.5,6.42e23,227900000,687,0.01,2,false
jupiter // Jupiter 2.36,69911,1.90e27,778600000,4333,20,4,true
saturn // Saturn 0.916,58232,5.68e26,1433500000,10759,1,7,true
uranus // Uranus 0.889,25362,8.68e25,2872500000,30687,1.3,13,true
neptune // Neptune 1.12,24622,1.02e26,4495100000,60190,1.5,2,true
)Now running the go generate command will generate the following code in a new file called planets_enums.go
// Code generated by goenums. DO NOT EDIT.
// This file was generated by github.com/zarldev/goenums
// using the command:
// goenums planets.go
package solarsystem
import (
"bytes"
"database/sql/driver"
"fmt"
"strconv"
)
type Planet struct {
planet
Gravity float64
RadiusKm float64
MassKg float64
OrbitKm float64
OrbitDays float64
SurfacePressureBars float64
Moons int
Rings bool
}
type planetsContainer struct {
UNKNOWN Planet
MERCURY Planet
VENUS Planet
EARTH Planet
MARS Planet
JUPITER Planet
SATURN Planet
URANUS Planet
NEPTUNE Planet
}
var Planets = planetsContainer{
MERCURY: Planet{
planet: mercury,
Gravity: 0.378,
RadiusKm: 2439.7,
MassKg: 3.3e23,
OrbitKm: 57910000,
OrbitDays: 88,
SurfacePressureBars: 0.0000000001,
Moons: 0,
Rings: false,
},
VENUS: Planet{
planet: venus,
Gravity: 0.907,
RadiusKm: 6051.8,
MassKg: 4.87e24,
OrbitKm: 108200000,
OrbitDays: 225,
SurfacePressureBars: 92,
Moons: 0,
Rings: false,
},
EARTH: Planet{
planet: earth,
Gravity: 1,
RadiusKm: 6378.1,
MassKg: 5.97e24,
OrbitKm: 149600000,
OrbitDays: 365,
SurfacePressureBars: 1,
Moons: 1,
Rings: false,
},
MARS: Planet{
planet: mars,
Gravity: 0.377,
RadiusKm: 3389.5,
MassKg: 6.42e23,
OrbitKm: 227900000,
OrbitDays: 687,
SurfacePressureBars: 0.01,
Moons: 2,
Rings: false,
},
JUPITER: Planet{
planet: jupiter,
Gravity: 2.36,
RadiusKm: 69911,
MassKg: 1.90e27,
OrbitKm: 778600000,
OrbitDays: 4333,
SurfacePressureBars: 20,
Moons: 4,
Rings: true,
},
SATURN: Planet{
planet: saturn,
Gravity: 0.916,
RadiusKm: 58232,
MassKg: 5.68e26,
OrbitKm: 1433500000,
OrbitDays: 10759,
SurfacePressureBars: 1,
Moons: 7,
Rings: true,
},
URANUS: Planet{
planet: uranus,
Gravity: 0.889,
RadiusKm: 25362,
MassKg: 8.68e25,
OrbitKm: 2872500000,
OrbitDays: 30687,
SurfacePressureBars: 1.3,
Moons: 13,
Rings: true,
},
NEPTUNE: Planet{
planet: neptune,
Gravity: 1.12,
RadiusKm: 24622,
MassKg: 1.02e26,
OrbitKm: 4495100000,
OrbitDays: 60190,
SurfacePressureBars: 1.5,
Moons: 2,
Rings: true,
},
}
func (c planetsContainer) All() []Planet {
return []Planet{
c.MERCURY,
c.VENUS,
c.EARTH,
c.MARS,
c.JUPITER,
c.SATURN,
c.URANUS,
c.NEPTUNE,
}
}
var invalidPlanet = Planet{}
func ParsePlanet(a any) (Planet, error) {
res := invalidPlanet
switch v := a.(type) {
case Planet:
return v, nil
case []byte:
res = stringToPlanet(string(v))
case string:
res = stringToPlanet(v)
case fmt.Stringer:
res = stringToPlanet(v.String())
case int:
res = intToPlanet(v)
case int64:
res = intToPlanet(int(v))
case int32:
res = intToPlanet(int(v))
}
return res, nil
}
func stringToPlanet(s string) Planet {
switch s {
case "unknown":
return Planets.UNKNOWN
case "Mercury":
return Planets.MERCURY
case "Venus":
return Planets.VENUS
case "Earth":
return Planets.EARTH
case "Mars":
return Planets.MARS
case "Jupiter":
return Planets.JUPITER
case "Saturn":
return Planets.SATURN
case "Uranus":
return Planets.URANUS
case "Neptune":
return Planets.NEPTUNE
}
return invalidPlanet
}
func intToPlanet(i int) Planet {
if i < 0 || i >= len(Planets.All()) {
return invalidPlanet
}
return Planets.All()[i]
}
func ExhaustivePlanets(f func(Planet)) {
for _, p := range Planets.All() {
f(p)
}
}
var validPlanets = map[Planet]bool{
Planets.MERCURY: true,
Planets.VENUS: true,
Planets.EARTH: true,
Planets.MARS: true,
Planets.JUPITER: true,
Planets.SATURN: true,
Planets.URANUS: true,
Planets.NEPTUNE: true,
}
func (p Planet) IsValid() bool {
return validPlanets[p]
}
func (p Planet) MarshalJSON() ([]byte, error) {
return []byte(`"` + p.String() + `"`), nil
}
func (p *Planet) UnmarshalJSON(b []byte) error {
b = bytes.Trim(bytes.Trim(b, `"`), ` `)
newp, err := ParsePlanet(b)
if err != nil {
return err
}
*p = newp
return nil
}
func (p *Planet) Scan(value any) error {
newp, err := ParsePlanet(value)
if err != nil {
return err
}
*p = newp
return nil
}
func (p Planet) Value() (driver.Value, error) {
return p.String(), nil
}
func _() {
// An "invalid array index" compiler error signifies that the constant values have changed.
// Re-run the goenums command to generate them again.
// Does not identify newly added constant values unless order changes
var x [1]struct{}
_ = x[unknown-0]
_ = x[mercury-1]
_ = x[venus-2]
_ = x[earth-3]
_ = x[mars-4]
_ = x[jupiter-5]
_ = x[saturn-6]
_ = x[uranus-7]
_ = x[neptune-8]
}
const _planets_name = "unknownMercuryVenusEarthMarsJupiterSaturnUranusNeptune"
var _planets_index = [...]uint16{0, 7, 14, 19, 24, 28, 35, 41, 47, 54}
func (i planet) String() string {
if i < 0 || i >= planet(len(_planets_index)-1) {
return "planets(" + (strconv.FormatInt(int64(i), 10) + ")")
}
return _planets_name[_planets_index[i]:_planets_index[i+1]]
}With the above code generated we can use the ExhaustivePlanets to iterate over all Enums for example:
package main
import (
"fmt"
"github.com/zarldev/goenums/examples/solarsystem"
)
func main() {
weightKg := 100.0
solarsystem.ExhaustivePlanets(func(p solarsystem.Planet) {
// calculate weight on each planet
gravity := p.Gravity
planetMass := weightKg * gravity
fmt.Printf("Weight on %s is %fKg with gravity %f\n", p, planetMass, gravity)
})
}Also the fact that the enums are concrete types with no way to instantiate the nested struct means that you can't just pass the int representation of the enum into the generated wrapper struct.
The above Status and Planet examples can be found in the examples directory. There is also a DiscountType example to show handling of camelCase formatted input enums.
