How to bind a struct to all generated Models?

[darmie]

What happened?

I want to bind gorm.Model struct to all generated models like this

What did you expect?

type User struct {
    gorm.Model  //<-- here
    ID Int
}

Minimal graphql.schema and models to reproduce

type User {
   id:ID!
}

versions

• gqlgen version v0.15.1
• go version 0.17?
• go modules

[rmortes]

Hi there! I've been using go for around the last 8 hours, so I don't know how legal this is, but I had the same question as you and I solved it with this code:

Code

// generate/main.go
package main

import (
	"fmt"
	"go/importer"
	"go/token"
	"os"

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

func mutateHook(b *modelgen.ModelBuild) *modelgen.ModelBuild {
	fset := token.NewFileSet()
	tpatata, err := importer.ForCompiler(fset, "source", nil).Import("gorm.io/gorm")

	if err != nil {
		panic("Error importing gorm" + err.Error())
	}

	for _, model := range b.Models {
		model.Fields = append(model.Fields, &modelgen.Field{Type: tpatata.Scope().Lookup("Model").Type()})
		for _, field := range model.Fields {
			field.Tag += ` test"`
		}

	}

	return b
}

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

	// Attaching the mutation function onto modelgen plugin
	p := modelgen.Plugin{
		MutateHook: mutateHook,
	}

	err = api.Generate(cfg, api.ReplacePlugin(&p))

	if err != nil {
		fmt.Fprintln(os.Stderr, err.Error())
		os.Exit(3)
	}
}

It took me a while to figure out how the mutateHook works, and I took me a lot to realize how to import/create a types.Type, but I think I got it. Currently, this code is generating the following code:

Code generated

// Code generated by github.com/99designs/gqlgen, DO NOT EDIT.

package model

import (
	"gorm.io/gorm"
)

type NewTodo struct {
	Text       string `json:"text" test"`
	UserID     string `json:"userId" test"`
	gorm.Model ` test"`
}

type NewUser struct {
	Name       string `json:"name" test"`
	gorm.Model ` test"`
}

type Todo struct {
	ID         string `json:"id" test"`
	Text       string `json:"text" test"`
	Done       bool   `json:"done" test"`
	User       *User  `json:"user" test"`
	gorm.Model ` test"`
}

type User struct {
	ID         string `json:"id" test"`
	Name       string `json:"name" test"`
	gorm.Model ` test"`
}

From the following schema:

Schema

# GraphQL schema example
#
# https://gqlgen.com/getting-started/

type Todo {
  id: ID!
  text: String!
  done: Boolean!
  user: User!
}

type User {
  id: ID!
  name: String!
}

type Query {
  todos: [Todo!]!
  users: [User!]!
}

input NewTodo {
  text: String!
  userId: String!
}

input NewUser {
  name: String!
}

type Mutation {
  createTodo(input: NewTodo!): Todo!
  createUser(input: NewUser!): User!
}

type Subscription {
  testSub: String
}

It's not perfect, but as you can see it's adding gorm.Model to the struct. Also, since we can add arbitrary tags, I reckon we can somehow use graphql annotations to add gorm tags (primaryKey, unique...) instead of importing the entire gorm.Model

[rmortes]

Hey, so, small update: I've updated the plugin, and I made it react to directives. You can now mark types to make them include gorm.Model and mark fields to add gorm related metadata to their tags. I've also added "belogs to" relationships as a proof of concept and it looks like it working nicely.

Basically, you can now turn this:

schema.graphqls

# GraphQL schema example
#
# https://gqlgen.com/getting-started/

directive @db on OBJECT
directive @gorm(
  value: String
  belongsTo: String
) on FIELD_DEFINITION

type Todo @db {
  id: ID! @gorm(value: "primaryKey")
  text: String!
  done: Boolean!
  user: User! @gorm(belongsTo: "User")
}

type User @db {
  id: ID! @gorm(value: "primaryKey")
  name: String! @gorm(value: "unique")
}

type Query {
  todos: [Todo!]!
  users: [User!]!
}

input NewTodo {
  text: String!
  userId: String!
}

input NewUser {
  name: String!
}

type Mutation {
  createTodo(input: NewTodo!): Todo!
  createUser(input: NewUser!): User!
}

type Subscription {
  testSub: String
}

Into this:

models_gen.go

// Code generated by github.com/99designs/gqlgen, DO NOT EDIT.

package model

import (
	"gorm.io/gorm"
)

type NewTodo struct {
	Text   string `json:"text"`
	UserID string `json:"userId"`
}

type NewUser struct {
	Name string `json:"name"`
}

type Todo struct {
	gorm.Model ``
	ID         string `json:"id" gorm:"primaryKey"`
	Text       string `json:"text"`
	Done       bool   `json:"done"`
	User       *User  `json:"user"`
	UserID     string ``
}

type User struct {
	gorm.Model ``
	ID         string `json:"id" gorm:"primaryKey"`
	Name       string `json:"name" gorm:"unique"`
}

The code is a bit more complex now, so if you still have a use case for this concept, let me know and I'll upload the code to a repo

Cheers!

[nephix]

Hey @rmortes have you published this already somewhere?

[rmortes]

I don't think so... I'll try to look for that code, but it's probably lost, sorry!

[nephix]

No worries, thanks