Note: 0.9.x contains breaking API changes. Go here for previous readme.
yarn add gqtx
gqtx is a thin layer on top of graphql-js for writing a type-safe GraphQL server in TypeScript. It provides you with a set of helper functions to create an intermediate representation of a GraphQL schema, and then converts that schema to a raw graphql-js schema. So you get to use everything from the reference implementation of GraphQL, but with way more type safety.
If a schema compiles, the following holds:
- The type of a field agrees with the return type of the resolver.
- The arguments of a field agrees with the accepted arguments of the resolver.
- The source of a field agrees with the type of the object to which it belongs.
- The return type of the resolver will not be input types (InputObject)
- The arguments of a field will not be abstract types (Interface, Union)
- The context argument for all resolver functions in a schema agree.
Most importantly, we achieve all this without having to:
- Set up code generation tools
- Write SDL and having your schema partially defined in code and in a DSL file
- Require special compiler magic such as
reflect-metadataand decorators
import { Gql, buildGraphQLSchema } from 'gqtx';
enum Role {
Admin,
User,
}
type User = {
id: string;
role: Role;
name: string;
};
const users: User[] = [
{ id: '1', role: Role.Admin, name: 'Sikan' },
{ id: '2', role: Role.User, name: 'Nicole' },
];
// We can declare the app context type once, and it will
// be automatically inferred for all our resolvers
declare module "gqtx" {
interface GqlContext {
viewerId: number;
users: User[];
}
}
const RoleEnum = Gql.Enum({
name: 'Role',
description: 'A user role',
values: [
{ name: 'Admin', value: Role.Admin },
{ name: 'User', value: Role.User },
],
});
const UserType = Gql.Object<User>({
name: 'User',
description: 'A User',
fields: () => [
Gql.Field({ name: 'id', type: Gql.NonNull(Gql.ID) }),
Gql.Field({ name: 'role', type: Gql.NonNull(RoleEnum) }),
Gql.Field({ name: 'name', type: Gql.NonNull(Gql.String) }),
],
});
const Query = Gql.Query({
fields: [
Gql.Field({
name: 'userById',
type: UserType,
args: {
id: Gql.Arg({ type: Gql.NonNullInput(Gql.ID) }),
},
resolve: (_, args, ctx) => {
// `args` is automatically inferred as { id: string }
// `ctx` (context) is also automatically inferred as { viewerId: number, users: User[] }
const user = ctx.users.find((u) => u.id === args.id);
// Also ensures we return an `User | null | undefined` type
return user
},
}),
],
});
const schema = buildGraphQLSchema({
query: Query,
});import express from 'express';
import graphqlHTTP from 'express-graphql';
const app = express();
app.use(
'/graphql',
graphqlHTTP({
schema,
graphiql: true,
})
);
app.listen(4000);We recommend using TypeScript strict mode in order to have the best developer experience.
tsconfig.json
{
"compilerOptions": {
+ "strict": true
}
}- We created an intermediate representation of a GraphQL schema via the helper functions exported by this library.
- Then, we converted the schema to a real graphql-js schema by calling
buildGraphQLSchemaat server startup time. - Used existing express middleware
express-graphqlto server our schema withgraphiqlexplorer - That's it! We get a fully type-safe server with almost zero type annotation needed