({ query }) => {
   const definition = getMainDefinition(query);
   return (
     definition.kind === "OperationDefinition" &&
     definition.operation === "subscription"
   );
 },

export function graphql(
  resolver: Resolver,
  document: DocumentNode,
  rootValue?: any,
  contextValue?: any,
  variableValues?: VariableMap,
  execOptions: ExecOptions = {},
) {
  const mainDefinition = getMainDefinition(document);

  const fragments = getFragmentDefinitions(document);
  const fragmentMap = createFragmentMap(fragments);

  const resultMapper = execOptions.resultMapper;

  // Default matcher always matches all fragments
  const fragmentMatcher = execOptions.fragmentMatcher || (() => true);

  const execContext: ExecContext = {
    fragmentMap,
    contextValue,
    variableValues,
    resultMapper,
    resolver,
    fragmentMatcher,
  };

  return executeSelectionSet(
    mainDefinition.selectionSet,
    rootValue,
    execContext,
  );
}

  /**
   * Based on graphql function from graphql-js:
   *
   * graphql(
   *   schema: GraphQLSchema,
   *   requestString: string,
   *   rootValue?: ?any,
   *   contextValue?: ?any,
   *   variableValues?: ?{[key: string]: any},
   *   operationName?: ?string
   * ): Promise<GraphQLResult>
   *
   * The default export as of graphql-anywhere is sync as of 4.0,
   * but below is an exported alternative that is async.
   * In the 5.0 version, this will be the only export again
   * and it will be async
   *
   */
  private executeStoreQuery({
    query,
    rootValue,
    contextValue,
    variableValues,
    // Default matcher always matches all fragments
    fragmentMatcher = defaultFragmentMatcher,
  }: ExecStoreQueryOptions): ExecResult {
    const mainDefinition = getMainDefinition(query);
    const fragments = getFragmentDefinitions(query);
    const fragmentMap = createFragmentMap(fragments);
    const execContext: ExecContext = {
      query,
      fragmentMap,
      contextValue,
      variableValues,
      fragmentMatcher,
    };

    return this.executeSelectionSet({
      selectionSet: mainDefinition.selectionSet,
      rootValue,
      execContext,
    });
  }

 ({ query }) => {
   const { kind, operation } = getMainDefinition(query);
   queryOrMutationLink['options'].headers = new HttpHeaders({
     Authorization: localStorage.getItem('token') ? `Bearer ${localStorage.getItem('token')}` : ''
   });
   return kind === 'OperationDefinition' && operation === 'subscription';
 },

  private async resolveDocument<TData>(
    document: DocumentNode,
    rootValue: TData,
    context: any = {},
    variables: VariableMap = {},
    fragmentMatcher: FragmentMatcher = () => true,
    onlyRunForcedResolvers: boolean = false,
  ) {
    const mainDefinition = getMainDefinition(document);
    const fragments = getFragmentDefinitions(document);
    const fragmentMap = createFragmentMap(fragments);

    const definitionOperation = (mainDefinition as OperationDefinitionNode)
      .operation;

    const defaultOperationType = definitionOperation
      ? capitalizeFirstLetter(definitionOperation)
      : 'Query';

    const { cache, client } = this;
    const execContext: ExecContext = {
      fragmentMap,
      context: {
        ...context,
        cache,
        client,
      },
      variables,
      fragmentMatcher,
      defaultOperationType,
      exportedVariables: {},
      onlyRunForcedResolvers,
    };

    return this.resolveSelectionSet(
      mainDefinition.selectionSet,
      rootValue,
      execContext,
    ).then(result => ({
      result,
      exportedVariables: execContext.exportedVariables,
    }));
  }

 ({ query }) => {
   const { kind, operation }: any = getMainDefinition(query);
   return kind === "OperationDefinition" && operation === "subscription";
 },

 ({ query }) => {
   const { kind, operation } = getMainDefinition(query);
   return kind === 'OperationDefinition' && operation === 'subscription';
 },

 // split based on operation type
 ({query}) => {
   const {kind, operation} = getMainDefinition(
     query,
   ) as OperationDefinitionNode
   return kind === 'OperationDefinition' && operation === 'subscription'
 },

    public request(
      operation: Operation,
      forward: NextLink = () => Observable.of({ data: {} }),
    ): Observable<FetchResult> {
      if (typeDefs) {
        const directives = 'directive @client on FIELD';

        const definition = normalizeTypeDefs(typeDefs);

        operation.setContext(({ schemas = [] }) => ({
          schemas: schemas.concat([{ definition, directives }]),
        }));
      }

      const isClient = hasDirectives(['client'], operation.query);

      if (!isClient) return forward(operation);

      const resolvers =
        typeof clientStateConfig.resolvers === 'function'
          ? clientStateConfig.resolvers()
          : clientStateConfig.resolvers;
      const server = removeClientSetsFromDocument(operation.query);
      const { query } = operation;
      const type =
        capitalizeFirstLetter(
          (getMainDefinition(query) || ({} as any)).operation,
        ) || 'Query';

      const resolver = (fieldName, rootValue = {}, args, context, info) => {
        const { resultKey } = info;

        // rootValue[fieldName] is where the data is stored in the "canonical model"
        // rootValue[info.resultKey] is where the user wants the data to be.
        // If fieldName != info.resultKey -- then GraphQL Aliases are in play
        // See also:
        // - https://github.com/apollographql/apollo-client/tree/master/packages/graphql-anywhere#resolver-info
        // - https://github.com/apollographql/apollo-link-rest/pull/113

        // Support GraphQL Aliases!
        const aliasedNode = rootValue[resultKey];
        const preAliasingNode = rootValue[fieldName];
        const aliasNeeded = resultKey !== fieldName;

        // If aliasedValue is defined, some other link or server already returned a value
        if (aliasedNode !== undefined || preAliasingNode !== undefined) {
          return aliasedNode || preAliasingNode;
        }

        // Look for the field in the custom resolver map
        const resolverMap = resolvers[(rootValue as any).__typename || type];
        if (resolverMap) {
          const resolve = resolverMap[fieldName];
          if (resolve) return resolve(rootValue, args, context, info);
        }

        // TODO: the proper thing to do here is throw an error saying to
        // add `client.onResetStore(link.writeDefaults);`
        // waiting on https://github.com/apollographql/apollo-client/pull/3010

        return (
          // Support nested fields
          (aliasNeeded ? aliasedNode : preAliasingNode) ||
          (defaults || {})[fieldName]
        );
      };

      if (server) operation.query = server;
      const obs =
        server && forward
          ? forward(operation)
          : Observable.of({
              data: {},
            });

      return new Observable(observer => {
        // Works around race condition between completion and graphql execution
        // finishing. If complete is called during the graphql call, we will
        // miss out on the result, since the observer will have completed
        let complete = false;
        let handlingNext = false;
        obs.subscribe({
          next: ({ data, errors }) => {
            const observerErrorHandler = observer.error.bind(observer);
            const context = operation.getContext();

            handlingNext = true;
            //data is from the server and provides the root value to this GraphQL resolution
            //when there is no resolver, the data is taken from the context
            graphql(resolver, query, data, context, operation.variables, {
              fragmentMatcher,
            })
              .then(nextData => {
                observer.next({
                  data: nextData,
                  errors,
                });
                if (complete) {
                  observer.complete();
                }
//.........这里部分代码省略.........