A GraphQL utility to generate Typescript from Schema Definition
This project is inspired by Apollo-codegen. Currently apollo-codegen
only generate TypeScripts for GraphQL Client.
The shape of the generated type is based on the client's query strings.
This module aim to do the Server counterpart: from a Schema Definition, generate the
types to make it type-safed when developing GraphQL server (mainly resolvers)
Features
Generate Typescript from Schema Definition (1-1 mapping from GQL type to TypeScript)
Convert GraphQL description into JSDoc, include deprecated directive
Usage
import { generateTypeScriptTypes } from 'graphql-schema-typescript';
generateTypeScriptTypes(schema, outputPath, options)
.then(() => {
console.log('DONE');
process.exit(0);
})
.catch(err =>{
console.error(err);
process.exit(1);
});
You can then bootstrap this script on your dev server,
or use something like ts-node to execute it directly
CLIs
- You can also use CLIs to generate your TypeScript instead of writing code
- Instead of providing a schema, you need to provide a folder that contains your type definitions,
written in .gql or .graphql extensions
- Use
graphql-schema-typescript generate-ts --help
for more details
Type Resolvers
The file generated will have some types that can make it type-safed when writing resolver:
- Args type in your resolve function is now type-safed
- Parent type and resolve result is default to
any
, but could be overwritten in your code
For example, if you schema is like this:
schema {
query: RootQuery
}
type RootQuery {
Users(input: UserFilter): [User!]!
}
input UserFilter {
username: [String]
}
type User {
firstName: String!
}
Then the tools will generate TypeScripts like this:
export interface GQLResolver {
RootQuery?: GQLRootQueryTypeResolver;
User?: GQLUserTypeResolver;
}
export interface GQLRootQueryTypeResolver {
Users?: RootQueryToUsersResolver;
}
export interface RootQueryToUsersArgs {
Users?: GQLUserFilter;
}
export interface RootQueryToUsersResolver<TParent = any, TResult = any> {
(parent: TParent, args: RootQueryToUsersArgs, context: any, info: GraphQLResolveInfo): TResult;
}
In this example, if you are not using graphql-tools,
you can still use RootQueryToUsersResolver
type to make your args type safed.
Default TParent & TResult
In version 1.2.2, a strategy for generating default TParent and TResult has been implemented
by setting smartTParent
and smartTResult
options to true.
If both options are set to true, the resolver will be generated as follow:
export interface RootQueryToUsersResolver<TParent = undefined, TResult = Array<GQLUser> {
(parent: TParent, args: RootQueryToUsersArgs, context: any, info: GraphQLResolveInfo): TResult;
}
However, since RootQueryToUsersResolver
usually will be asynchronous operation,
the default TResult would not be too helpful, as developers would most likely overwrite it to Promise<Array<GQLUser>>
. Therefore, another option , asyncResult
, was implemented. This option
basically allow resolver to return promises
export interface RootQueryToUsersResolver<TParent = undefined, TResult = Array<GQLUser> {
(parent: TParent, args: RootQueryToUsersArgs, context: any, info: GraphQLResolveInfo): Promise<TResult> | TResult;
}
export interface RootQueryToUsersResolver<TParent = undefined, TResult = Array<GQLUser> {
(parent: TParent, args: RootQueryToUsersArgs, context: any, info: GraphQLResolveInfo): Promise<TResult>;