Add fetchFunc option to client constructor (#1097)

* Add  option to client constructor

* Fix lint

* Define globalThis for Firefox build

Without this the exported symbol `KintoHttpClient` is not reachable.
This build has change that is responsible of this regression:

```diff

 (function (global, factory) {
     typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
     typeof define === 'function' && define.amd ? define(factory) :
-    (global = global || self, global.KintoHttpClient = factory());
+    (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.KintoHttpClient = factory());
 }(this, (function () { 'use strict';

```

* add types to fetchFunc option (#1098)

Co-authored-by: Dylan Staley <88163+dstaley@users.noreply.github.com>

fx-src/jsm_prefix.js

@@ -19,6 +19,7 @@
  */
 
 const global = this;
+const globalThis = this;
 
 var EXPORTED_SYMBOLS = ["KintoHttpClient"];
 

src/base.ts

@@ -29,6 +29,7 @@ import {
   User,
   Emitter,
   HttpMethod,
+  FetchFunction,
 } from "./types";
 import Collection from "./collection";
 
@@ -47,6 +48,7 @@ export interface KintoClientOptions {
   requestMode?: RequestMode;
   timeout?: number;
   batch?: boolean;
+  fetchFunc?: FetchFunction;
 }
 
 export interface PaginatedParams {
@@ -107,6 +109,7 @@ export default class KintoClientBase {
    * @param  {String}       [options.bucket="default"]    The default bucket to use.
    * @param  {String}       [options.requestMode="cors"]  The HTTP request mode (from ES6 fetch spec).
    * @param  {Number}       [options.timeout=null]        The request timeout in ms, if any.
+   * @param  {Function}     [options.fetchFunc=fetch]     The function to be used to execute HTTP requests.
    */
   constructor(remote: string, options: KintoClientOptions) {
     if (typeof remote !== "string" || !remote.length) {
@@ -145,13 +148,13 @@ export default class KintoClientBase {
 
     this.endpoints = endpoints;
 
-    const { requestMode, timeout } = options;
+    const { fetchFunc, requestMode, timeout } = options;
     /**
      * The HTTP instance.
      * @ignore
      * @type {HTTP}
      */
-    this.http = new HTTP(this.events, { requestMode, timeout });
+    this.http = new HTTP(this.events, { fetchFunc, requestMode, timeout });
     this._registerHTTPEvents();
   }
 

src/errors.ts

@@ -1,3 +1,5 @@
+import { FetchResponse } from "./types";
+
 /**
  * Kinto server error code descriptors.
  */
@@ -45,11 +47,11 @@ class NetworkTimeoutError extends Error {
 
 class UnparseableResponseError extends Error {
   public status: number;
-  public response: Response;
+  public response: FetchResponse;
   public stack?: string;
   public error: Error;
 
-  constructor(response: Response, body: string, error: Error) {
+  constructor(response: FetchResponse, body: string, error: Error) {
     const { status } = response;
 
     super(
@@ -90,10 +92,10 @@ export interface ServerResponseObject {
  * responses (which become UnparseableResponseErrors, above).
  */
 class ServerResponse extends Error {
-  public response: Response;
+  public response: FetchResponse;
   public data?: ServerResponseObject;
 
-  constructor(response: Response, json?: ServerResponseObject) {
+  constructor(response: FetchResponse, json?: ServerResponseObject) {
     const { status } = response;
     let { statusText } = response;
     let errnoMsg;

src/http.ts

@@ -5,11 +5,12 @@ import {
   UnparseableResponseError,
   ServerResponseObject,
 } from "./errors";
-import { Emitter } from "./types";
+import { Emitter, FetchFunction, FetchHeaders, FetchResponse } from "./types";
 
 interface HttpOptions {
   timeout?: number | null;
   requestMode?: RequestMode;
+  fetchFunc?: FetchFunction;
 }
 
 interface RequestOptions {
@@ -19,7 +20,7 @@ interface RequestOptions {
 export interface HttpResponse<T> {
   status: number;
   json: T;
-  headers: Headers;
+  headers: FetchHeaders;
 }
 
 /**
@@ -51,6 +52,7 @@ export default class HTTP {
   public events?: Emitter;
   public requestMode: RequestMode;
   public timeout: number;
+  public fetchFunc: FetchFunction;
 
   /**
    * Constructor.
@@ -80,12 +82,18 @@ export default class HTTP {
      * @type {Number}
      */
     this.timeout = options.timeout || HTTP.defaultOptions.timeout!;
+
+    /**
+     * The fetch() function.
+     * @type {Function}
+     */
+    this.fetchFunc = options.fetchFunc || globalThis.fetch.bind(globalThis);
   }
 
   /**
    * @private
    */
-  timedFetch(url: string, options: RequestInit): Promise<Response> {
+  timedFetch(url: string, options: RequestInit): Promise<FetchResponse> {
     let hasTimedout = false;
     return new Promise((resolve, reject) => {
       // Detect if a request has timed out.
@@ -112,7 +120,7 @@ export default class HTTP {
           }
         };
       }
-      fetch(url, options)
+      this.fetchFunc(url, options)
         .then(proceedWithHandler(resolve))
         .catch(proceedWithHandler(reject));
     });
@@ -121,7 +129,7 @@ export default class HTTP {
   /**
    * @private
    */
-  async processResponse<T>(response: Response): Promise<HttpResponse<T>> {
+  async processResponse<T>(response: FetchResponse): Promise<HttpResponse<T>> {
     const { status, headers } = response;
     const text = await response.text();
     // Check if we have a body; if so parse it as JSON.
@@ -206,7 +214,7 @@ export default class HTTP {
     }
   }
 
-  _checkForDeprecationHeader(headers: Headers): void {
+  _checkForDeprecationHeader(headers: FetchHeaders): void {
     const alertHeader = headers.get("Alert");
     if (!alertHeader) {
       return;
@@ -224,7 +232,7 @@ export default class HTTP {
     }
   }
 
-  _checkForBackoffHeader(headers: Headers): void {
+  _checkForBackoffHeader(headers: FetchHeaders): void {
     let backoffMs;
     const backoffHeader = headers.get("Backoff");
     const backoffSeconds = backoffHeader ? parseInt(backoffHeader, 10) : 0;
@@ -238,7 +246,7 @@ export default class HTTP {
     }
   }
 
-  _checkForRetryAfterHeader(headers: Headers): number | undefined {
+  _checkForRetryAfterHeader(headers: FetchHeaders): number | undefined {
     const retryAfter = headers.get("Retry-After");
     if (!retryAfter) {
       return;

src/types.ts

@@ -115,3 +115,22 @@ export interface Emitter {
   on(type: string, handler: (event?: any) => void): void;
   off(type: string, handler: (event?: any) => void): void;
 }
+
+export interface FetchHeaders {
+  keys(): IterableIterator<string> | string[];
+  entries(): IterableIterator<[string, string]> | [string, string][];
+  get(name: string): string | null;
+  has(name: string): boolean;
+}
+
+export interface FetchResponse {
+  status: number;
+  statusText: string;
+  text(): Promise<string>;
+  headers: FetchHeaders;
+}
+
+export type FetchFunction = (
+  input: RequestInfo,
+  init?: RequestInit | undefined
+) => Promise<FetchResponse>;