index.js

'use strict';

const { makeExecutableSchema, addMockFunctionsToSchema } = require('graphql-tools');
const { graphql, printSchema, buildClientSchema } = require('graphql');
const RelayMockNetworkLayerError = require('./RelayMockNetworkLayerError');

const defaultSchemaDefinitionOptions = {
    resolverValidationOptions: {
        // Silence error regarding missing Relay `Node` type
        // https://github.com/este/este/issues/1513#issuecomment-385752066
        requireResolversForResolveType: false,
    },
};

/**
 * @param {Object} networkConfig - The configuration for the mock network layer.
 * @param {(string|Object)} networkConfig.schema - If string, the graphql schema SDL. If object, the JSON introspection query.
 * @param {Object} networkConfig.mocks - Mock primative resolvers, passed directly to addMockFunctionsToSchema.
 * @param {Object} networkConfig.resolvers - Default resolvers for a schema.
 * @param {Function} [networkConfig.resolveQueryFromOperation] - If relay operation query text does not exist, used to resolve the query from the operation. Useful for persisted query support.
 */
module.exports = function getNetworkLayer({
    schema,
    mocks,
    resolvers,
    resolveQueryFromOperation,

    /** https://www.apollographql.com/docs/graphql-tools/mocking.html#Mocking-interfaces */
    preserveResolvers = false,

    /**
     * https://github.com/apollographql/graphql-tools/blob/master/src/Interfaces.ts#L125
     * @type IExecutableSchemaDefinition
     */
    ...schemaDefinitionOptions
}) {
    schemaDefinitionOptions = {
        ...defaultSchemaDefinitionOptions,
        ...schemaDefinitionOptions,
    };

    return function fetchQuery(operation, variableValues) {
        if (typeof schema === 'object' && schema.data) {
            schema = printSchema(buildClientSchema(schema.data));
        }

        const executableSchema = makeExecutableSchema({
            typeDefs: schema,
            resolvers,
            ...schemaDefinitionOptions,
        });

        // Add mocks, modifies schema in place
        addMockFunctionsToSchema({ schema: executableSchema, mocks, preserveResolvers });

        const query =
            (resolveQueryFromOperation && resolveQueryFromOperation(operation)) || operation.text;

        if (!query) {
            throw new Error(
                'Could not find query, ensure operation.text exists or pass resolveQueryFromOperation.'
            );
        }

        return graphql(executableSchema, query, null, null, variableValues).then(
            // Trigger Relay error in case of GraphQL errors (or errors in mutation response)
            // See https://github.com/facebook/relay/issues/1816

            result => {
                if (result.errors && result.errors.length > 0) {
                    return Promise.reject(new RelayMockNetworkLayerError(result.errors));
                }
                return Promise.resolve(result);
            }
        );
    };
}