plugins.md

linkTitle	Plugins
title	How to write plugins for gqlgen
description	Use plugins to customize code generation and integrate with other libraries
menu	main parent weight reference 10

Plugins provide a way to hook into the gqlgen code generation lifecycle. In order to use anything other than the default plugins you will need to create your own entrypoint:

Using a plugin

To use a plugin during code generation, you need to create a new entry point. Create generate.go in the same folder as resolver.go with the following code:

// go:build ignore

package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"time"

	"github.com/99designs/gqlgen/api"
	"github.com/99designs/gqlgen/codegen/config"
	"github.com/99designs/gqlgen/plugin/stubgen"
)

func main() {
	cfg, err := config.LoadConfigFromDefaultLocations()
	if err != nil {
		fmt.Fprintln(os.Stderr, "failed to load config", err.Error())
		os.Exit(2)
	}


	err = api.Generate(cfg,
		api.AddPlugin(yourplugin.New()), // This is the magic line
	)
	if err != nil {
		fmt.Fprintln(os.Stderr, err.Error())
		os.Exit(3)
	}
}

In resolver.go, add //go:generate go run generate.go (or replace //go:generate go tool gqlgen if you have it there).

Now you can run go generate ./... to generate code using your plugin.

Writing a plugin

There are currently only two hooks:

• MutateConfig: Allows a plugin to mutate the config before codegen starts. This allows plugins to add custom directives, define types, and implement resolvers. see modelgen for an example
• GenerateCode: Allows a plugin to generate a new output file, see stubgen for an example

Take a look at plugin.go for the full list of available hooks. These are likely to change with each release.