import { createSourceEventStream } from 'graphql'; import { isAsyncIterable, makeSubscribe, mapAsyncIterator, } from '@envelop/core'; import { handleMaybePromise } from '@whatwg-node/promise-helpers'; /** * This is a almost identical port from graphql-js subscribe. * The only difference is that a custom `execute` function can be injected for customizing the behavior. */ export const subscribe = (execute) => makeSubscribe(({ schema, document, rootValue, contextValue, variableValues, operationName, fieldResolver, subscribeFieldResolver, }) => { return handleMaybePromise(() => createSourceEventStream(schema, document, rootValue, contextValue, variableValues ?? undefined, operationName, subscribeFieldResolver), resultOrStream => { if (!isAsyncIterable(resultOrStream)) { return resultOrStream; } // Map every source value to a ExecutionResult value as described above. return mapAsyncIterator(resultOrStream, // For each payload yielded from a subscription, map it over the normal // GraphQL `execute` function, with `payload` as the rootValue. // This implements the "MapSourceToResponseEvent" algorithm described in // the GraphQL specification. The `execute` function provides the // "ExecuteSubscriptionEvent" algorithm, as it is nearly identical to the // "ExecuteQuery" algorithm, for which `execute` is also used. (payload) => execute({ schema, document, rootValue: payload, contextValue, variableValues, operationName, fieldResolver, })); }); });