gqlgenmarshal

gqlgenmarshal

Use Go Generate to autogen MarshalGQL and UnmarshalGQL functions for your enums/iotas.

Installation

Go >= 1.16

go install github.com/xplorfin/gqlgenmarshal@latest

Go < 1.16

go get -u github.com/xplorfin/gqlgenmarshal

Usage

Using the example type Carl:

package carl

//go:generate github.com/xplorfin/gqlgenmarshal -type=Carl

type Carl uint8

const (
	Herp Carl = iota
	Derp
	Merp
)

Run go generate ./... from the root of your project, and you'll get the following:

// Code generated by "gqlgenmarshal -type=Carl"; DO NOT EDIT.

package carl

import (
	"encoding/json"
	"fmt"
	"io"
)

func _() {
	// An "invalid array index" compiler error signifies that the constant values have changed.
	// Re-run the stringer command to generate them again.
	var x [1]struct{}
	_ = x[Herp-0]
	_ = x[Derp-1]
	_ = x[Merp-2]
}

func (i Carl) MarshalGQL(w io.Writer) {
	if err := json.NewEncoder(w).Encode(i); err != nil {
		panic(fmt.Errorf("error marshaling Carl"))
	}
}

func (i *Carl) UnmarshalGQL(v interface{}) error {
	check, ok := v.(int)
	if !ok {
		return fmt.Errorf("Carl must be a valid int value")
	}

	switch Carl(check) {
	case Herp:
		*i = Herp
	case Derp:
		*i = Derp
	case Merp:
		*i = Merp
	default:
		return fmt.Errorf("unknown Carl value %[1]v", check)
	}

	return nil
}

If your type implements fmt.Stringer (ie. has a String() method), then the generated code will encode/decode the string value of the sent/received data instead of the int value.

You can pass the -checkstringlowercase flag to make UnmarshalGQL check against the lowercase value of a string instead of whatever the raw result of <type>.String() returns.