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makeRemoteExecutableSchema.ts
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makeRemoteExecutableSchema.ts
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// This import doesn't actually import code - only the types.
// Don't use ApolloLink to actually construct a link here.
import { ApolloLink } from 'apollo-link';
import {
GraphQLFieldResolver,
GraphQLSchema,
buildSchema,
Kind,
GraphQLResolveInfo,
BuildSchemaOptions,
DocumentNode,
} from 'graphql';
import linkToFetcher, { execute } from './linkToFetcher';
import { Fetcher, Operation } from '../Interfaces';
import { addTypenameToAbstract } from './addTypenameToAbstract';
import { checkResultAndHandleErrors } from './checkResultAndHandleErrors';
import { observableToAsyncIterable } from './observableToAsyncIterable';
import mapAsyncIterator from './mapAsyncIterator';
import { Options as PrintSchemaOptions } from 'graphql/utilities/schemaPrinter';
import { cloneSchema } from '../utils';
import { stripResolvers, generateProxyingResolvers } from './resolvers';
import { addResolveFunctionsToSchema } from '../generate';
export type ResolverFn = (
rootValue?: any,
args?: any,
context?: any,
info?: GraphQLResolveInfo
) => AsyncIterator<any>;
export default function makeRemoteExecutableSchema({
schema: targetSchema,
link,
fetcher,
createResolver: customCreateResolver = createResolver,
buildSchemaOptions,
printSchemaOptions = { commentDescriptions: true }
}: {
schema: GraphQLSchema | string;
link?: ApolloLink;
fetcher?: Fetcher;
createResolver?: (fetcher: Fetcher) => GraphQLFieldResolver<any, any>;
buildSchemaOptions?: BuildSchemaOptions;
printSchemaOptions?: PrintSchemaOptions;
}): GraphQLSchema {
if (!fetcher && link) {
fetcher = linkToFetcher(link);
}
if (typeof targetSchema === 'string') {
targetSchema = buildSchema(targetSchema, buildSchemaOptions);
}
const remoteSchema = cloneSchema(targetSchema);
stripResolvers(remoteSchema);
function createProxyingResolver(
schema: GraphQLSchema,
operation: Operation,
): GraphQLFieldResolver<any, any> {
if (operation === 'query' || operation === 'mutation') {
return customCreateResolver(fetcher);
} else {
return createSubscriptionResolver(link);
}
}
const resolvers = generateProxyingResolvers(remoteSchema, [], createProxyingResolver);
addResolveFunctionsToSchema({
schema: remoteSchema,
resolvers,
resolverValidationOptions: {
allowResolversNotInSchema: true,
},
});
return remoteSchema;
}
export function createResolver(fetcher: Fetcher): GraphQLFieldResolver<any, any> {
return async (root, args, context, info) => {
const fragments = Object.keys(info.fragments).map(fragment => info.fragments[fragment]);
let query: DocumentNode = {
kind: Kind.DOCUMENT,
definitions: [info.operation, ...fragments]
};
query = addTypenameToAbstract(info.schema, query);
const result = await fetcher({
query,
variables: info.variableValues,
context: { graphqlContext: context }
});
return checkResultAndHandleErrors(result, info);
};
}
function createSubscriptionResolver(link: ApolloLink): ResolverFn {
return (root, args, context, info) => {
const fragments = Object.keys(info.fragments).map(fragment => info.fragments[fragment]);
let query: DocumentNode = {
kind: Kind.DOCUMENT,
definitions: [info.operation, ...fragments]
};
query = addTypenameToAbstract(info.schema, query);
const operation = {
query,
variables: info.variableValues,
context: { graphqlContext: context }
};
const observable = execute(link, operation);
const originalAsyncIterator = observableToAsyncIterable(observable);
return mapAsyncIterator(originalAsyncIterator, result => ({
[info.fieldName]: checkResultAndHandleErrors(result, info),
}));
};
}