Utilities

/**
 * Converts an observable to a promise, resolving with the first emitted value
 * @param observable - Observable to convert
 * @returns Promise that resolves with the first emitted value
 */
function toPromise<R>(observable: Observable<R>): Promise<R>;

import { execute, toPromise } from "apollo-link";

const link = new HttpLink("/graphql");
const operation = { query: gql`query { users { id } }` };

// Convert observable result to promise
const result = await toPromise(execute(link, operation));
console.log(result.data);

/**
 * @deprecated Use toPromise instead
 * Converts an observable to a promise
 */
function makePromise<R>(observable: Observable<R>): Promise<R>;

/**
 * Creates an observable from a promise
 * @param promise - Promise to convert
 * @returns Observable that emits the promise result
 */
function fromPromise<T>(promise: Promise<T>): Observable<T>;

import { fromPromise } from "apollo-link";

const dataPromise = fetch("/api/data").then(r => r.json());
const observable = fromPromise(dataPromise);

observable.subscribe({
  next: data => console.log(data),
  error: err => console.error(err)
});

/**
 * Creates an observable that immediately emits an error
 * @param errorValue - Error value to emit
 * @returns Observable that immediately errors
 */
function fromError<T>(errorValue: any): Observable<T>;

import { fromError } from "apollo-link";

// Create an error observable for testing or fallback scenarios
const errorObservable = fromError(new Error("Network unavailable"));

errorObservable.subscribe({
  error: err => console.error("Expected error:", err.message)
});

/**
 * Creates an Operation object from a GraphQL request with context methods
 * @param starting - Initial context object
 * @param operation - GraphQL request to enhance
 * @returns Operation with setContext, getContext, and toKey methods
 */
function createOperation(starting: any, operation: GraphQLRequest): Operation;

import { createOperation } from "apollo-link";
import gql from "graphql-tag";

const request = {
  query: gql`query GetUser($id: ID!) { user(id: $id) { name } }`,
  variables: { id: "123" },
  operationName: "GetUser"
};

const operation = createOperation({ headers: {} }, request);

// Use operation methods
operation.setContext({ headers: { Authorization: "Bearer token" } });
console.log(operation.getContext()); // { headers: { Authorization: "Bearer token" } }
console.log(operation.toKey()); // Unique key for this operation

/**
 * Extracts the operation name from a GraphQL AST
 * @param query - GraphQL query AST
 * @returns Operation name string or null
 */
function getOperationName(query: DocumentNode): string | null;

import { getOperationName } from "apollo-link";
import gql from "graphql-tag";

const query = gql`query GetUsers { users { id name } }`;
const operationName = getOperationName(query);
console.log(operationName); // "GetUsers"