@envelop/execute-subscription-event/esm/subscribe.js

import { createSourceEventStream } from 'graphql';
import { isAsyncIterable, makeSubscribe, mapAsyncIterator } from '@envelop/core';
import { handleMaybePromise } from '@whatwg-node/promise-helpers';
const validateSubscriptionArgsPromise = import('graphql').then(graphqlModule => graphqlModule
    .validateSubscriptionArgs);
function getSourceEventStream(args, validateSubscriptionArgs) {
    if (validateSubscriptionArgs) {
        const validatedArgs = validateSubscriptionArgs(args);
        if (!('schema' in validatedArgs)) {
            return { errors: validatedArgs };
        }
        // Cast away the installed graphql version's own overloads here for backwards compatability
        const createSourceEventStreamWithValidatedArgs = createSourceEventStream;
        return createSourceEventStreamWithValidatedArgs(validatedArgs);
    }
    const legacyCreateSourceEventStream = createSourceEventStream;
    return legacyCreateSourceEventStream(args.schema, args.document, args.rootValue, args.contextValue, args.variableValues ?? undefined, args.operationName, args.subscribeFieldResolver);
}
/**
 * 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(args => {
    const { schema, document, contextValue, variableValues, operationName, fieldResolver } = args;
    return handleMaybePromise(() => validateSubscriptionArgsPromise, (validateSubscriptionArgs) => handleMaybePromise(() => getSourceEventStream(args, validateSubscriptionArgs), (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,
        }));
    }));
});