Generating SDL

Warning This chapter applies only to the code first approach.

To generate a GraphQL SDL schema manually (i.e., without running an application, connecting to the database, hooking up resolvers, etc.), use the GraphQLSchemaBuilderModule:

async function generateSchema() {
  const app = await NestFactory.create(GraphQLSchemaBuilderModule);
  await app.init();

  const gqlSchemaFactory = app.get(GraphQLSchemaFactory);
  const schema = await gqlSchemaFactory.create([RecipesResolver]);
  console.log(printSchema(schema));
}

Hint The GraphQLSchemaBuilderModule and GraphQLSchemaFactory are imported from the @nestjs/graphql package. The printSchema function is imported from the graphql package.

Usage#

The gqlSchemaFactory.create() method takes an array of resolver class references. For example:

const schema = await gqlSchemaFactory.create([
  RecipesResolver,
  AuthorsResolver,
  PostsResolver,
]);

It also takes an optional second argument with an array of scalar classes:

const schema = await gqlSchemaFactory.create(
  [RecipesResolver, AuthorsResolver, PostsResolver],
  [DurationScalar, DateScalar],
);

Lastly, you can pass an options object (the same BuildSchemaOptions accepted by the buildSchemaOptions property of the GraphQLModule configuration):

const schema = await gqlSchemaFactory.create([RecipesResolver], {
  skipCheck: true,
  orphanedTypes: [],
});

• skipCheck: skip schema validation; boolean, defaults to false
• orphanedTypes: an array of classes to generate even though they aren't explicitly referenced (i.e., aren't part of the object graph). Normally, a class that is declared but not referenced anywhere in the graph is omitted.

Federation#

GraphQLSchemaFactory builds a plain GraphQL schema: it knows nothing about Apollo Federation. To get the SDL of a code first federated subgraph (for example, to pass it to rover subgraph check or rover supergraph compose), print it with printSubgraphSchema from @apollo/subgraph instead of printSchema, so that directives such as @key, @shareable or @external are kept:

import { printSubgraphSchema } from '@apollo/subgraph';

async function generateSchema() {
  const app = await NestFactory.create(GraphQLSchemaBuilderModule);
  await app.init();

  const gqlSchemaFactory = app.get(GraphQLSchemaFactory);
  const schema = await gqlSchemaFactory.create([UsersResolver], {
    orphanedTypes: [User],
  });
  console.log(printSubgraphSchema(schema));
}

For Federation 2, the printed SDL must also link the federation specification, or it is treated as a Federation 1 subgraph. Prepend the @link yourself, importing every federation directive your types use:

const sdl = `extend schema @link(url: "https://specs.apollo.dev/federation/v2.14", import: ["@key", "@shareable", "@external"])

${printSubgraphSchema(schema)}`;

Hint Entity types that are only referenced through _entities (for example, @extends stubs resolved with @ResolveReference()) aren't reachable from the root types, so pass them in orphanedTypes. Otherwise, the schema is generated without them.