graphql-codegen-go

Generate Go structs from your GraphQL schema.

This code generator helps you derive Go structures directly from GraphQL schema. The schema can be located either locally or can be fetched from GIT repository.

Install it using go get:

$ go get -u github.com/jkrajniak/graphql-codegen-go

Quick start

Simply, define the GQL schema

type Person {
  name: String!
  age: Int!
  weight: Int
  likes: [String]
  donts: [String!]
}

and save it, e.g. in schema.gql file. Then run the code generator

$ graphql-codegen-go -schemas schema.gql -packageName pkg -out models.go

As a result, you will get a models.go file with the following Go code

// Code generated by go generate; DO NOT EDIT.
// This file was generated from GraphQL schema schema.gql

package pkg

type Person struct {
	Name   string    `json:"name"`
	Age    int64     `json:"age"`
	Weight *int64    `json:"weight"`
	Likes  []*string `json:"likes"`
	Donts  []string  `json:"donts"`
}

Notice that not required (weight) fields are converted to the pointers. The packageName option is optional. The generator will try to derive the package name from the current running path of the code, or if run by go:generate from $GOPACKAGE env variable.

GIT

The schema does not have to be located locally. The program supports also Git repositories. Let's assume that you the schema.gql file is placed in github.com/orange/repo1 repository, inside a deployment directory. Then, to create the structures you can run the generator as follows

$ graphql-codegen-go -schemas https://github.com/orange/repo1.git/deployment/schema.gql -packageName pkg -out models.go

or via ssh

$ graphql-codegen-go -schemas git@github.com:orange/repo1.git/deployment/schema.gql -packageName pkg -out models.go

By default, the schema is pulled from the HEAD. To point a specific commit, you can place a commit hash after the file name, e.g.,

$ graphql-codegen-go -schemas git@github.com:orange/repo1.git/deployment/schema.gql#a56351vc -packageName pkg -out models.go

Moreover, you can also point the specific branch or tag by using @ sign

$ graphql-codegen-go -schemas git@github.com:orange/repo1.git/deployment/schema.gql@branch -packageName pkg -out models.go

or

$ graphql-codegen-go -schemas git@github.com:orange/repo1.git/deployment/schema.gql@tag1 -packageName pkg -out models.go

Entities

By default generator will output structures for all of the entities found in the schema. To output only a subset of structures you can use -entities option.

For example

$ graphql-codegen-go -schemas schema.gql -packageName pkg -out models.go -entities Person

will create file models.go only with a single structure Person, and all related dependent structures and enums.

YAML Config

Instead of command line parameters, the generator supports also a config file (-config). The example of the file can be found in examples/config/config.yml.

The structure of the YAML file is

schema: A list of schema files (it will be combined into one schema before parsing)
generates: A key-value map, where key is the name of the output Go file
    <output-file>:
      config:
        packageName: A package name
        entities: A list of entities to be included into the output Go file

Example

schema:
    - ./schema.graphql
    - ./types.graphql
    - https://github.com/jkrajniak/sc.git/schema1.gql
generates:
    internal/models.go:
      config:
        packageName: internal
        entities:
          - User
          - Person
    internal/abc/models.go:
      config:
        packageName: abc
        entities:
          - Action

After execution of the above config you will find two .go files (internal/models.go and internal/abc/models.go); the first will contain structures User and Person, and the second Action.

The GQL schema will be read from two local files, from GIT repository.

go:generate

The generator can work perfectly fine with the go:generate directive. The examples of how to include it can be found in examples/ directory.

Union

The union type is supported in the following way. Let's consider a schema

type Et {
  value: String
}

type Pt {
  label: String!
}

union Ett = Et | Pt

type Entity {
  id: String!
  etpt: Ett
}

The union type Ett is converted into a Go struct Ett

type Et struct {
	Value *string `json:"value"`
}

type Pt struct {
	Label string `json:"label"`
}

type Ett struct {
	TypeName string `json:"__typeName"`
	Et
	Pt
}

type Entity struct {
	Id   string `json:"id"`
	Etpt *Ett   `json:"etpt"`
}