xgql

xgql is a GraphQL schema manipulation tool and extensions. The idea is to parse graphQL schemas and extend the grammar to support other nice things such as includes. This is a useful tool to include in your CI pipeline in order to assemble your schemas into a single file.

Commands

Run xgql --help to get general help or xgql <command> --help to get help about a particular command.

Merge multiple GraphQL schemas

It's often useful if you need sanity, to break down large schemas into multiple files. The merge command merges the files back together into a single schema. The following command outputs the merged schema to stdout:

xgql merge tests/resources/schema1.graphql tests/resources/schema2.graphql

Some graphql vendors want comments formatted a certain way (I'm looking at you AWS). So you can use the --style option to format comments appropriately. AppSync in particular does not like enum values to have a desription so they will get scrubbed.

xgql merge --style appsync tests/resources/schema1.graphql tests/resources/schema2.graphql

Example

schema1.graphql

type Person {
  id: ID!
  name: String!
  age: Int!
  dob: MyDate!
}

type Query {
  allPersons(last: Int): [Person!]!
}

type Mutation {
  createPerson(name: String!, age: Int!): Person!
}

type Subscription {
  newPerson: Person!
}

schema {
  query: Query
  mutation: Mutation
  subscription: Subscription
}

schema2.graphql

"""
Custom definition of a date
"""
scalar MyDate

type Post {
  id: ID!
  title: String!
  author: Person!
}

input PostInput {
  title: String!
  author: Person!
}

type Query {
  # Lists all posts
  allPosts(title: String!): [Post!]!
}

type Mutation {
  """
  Creates a new post
  """
  createPost(post: PostInput!): Post!
}

Results in:

schema {
    query: Query
    mutation: Mutation
    subscription: Subscription
}

type Person {
    id: ID!
    name: String!
    age: Int!
    dob: MyDate!
}

input PostInput {
    title: String!
    author: Person!
}

type Post {
    id: ID!
    title: String!
    author: Person!
}

"""
Custom definition of a date
"""
scalar MyDate

type Subscription {
    newPerson: Person!
}

type Mutation {
    createPerson(
        name: String!
        age: Int!
    ): Person!
    """
    Creates a new post
    """
    createPost(
        post: PostInput!
    ): Post!
}

type Query {
    allPersons(
        last: Int
    ): [Person!]!
    """
    Lists all posts
    """
    allPosts(
        title: String!
    ): [Post!]!
}

The --fill option

If the --fill option is set, xgql will automatically add missing fields from interfaces inherited by a type. Example:

interface Person {
  id: ID!
  first_name: String
  last_name: String!
}

type Employee implements Person {
  employee_id: String!
}

becomes:

interface Person {
    id: ID!
    first_name: String
    last_name: String!
}

type Employee implements Person {
    employee_id: String!
    id: ID!
    first_name: String
    last_name: String!
}

Syntax check a GraphQL schema

The syntax command simply checks that the content of the file is well formatted. It does not try to check that any of the types are valid, etc...

xgql syntax tests/resources/type.graphql tests/resources/type-invalid.graphql

will output something like:

- tests/resources/type.graphql: OK
- tests/resources/type-invalid.graphql: ERROR
invalid syntax at line 3 col 25:

    variable(): Date! What's this doing here?

The syntax command will exit with code 1 is any error was found, 0 otherwise. This can be useful for CI.

Introspection query

The introspect command simulates running a basic introspection query against the schema. It produces a valid instrospection JSON from the schema file.

xgql introspect schema.graphql