feat: add an adapter option for request overrides (#38)

README.md

@@ -76,6 +76,14 @@ gaxios.request({url: '/data'}).then(...);
   // The timeout for the HTTP request. Defaults to 0.
   timeout: 1000,
 
+  // Optional method to override making the actual HTTP request. Useful
+  // for writing tests.
+  adapter?: (options) => {
+    return {
+      data: 'your data'
+    }
+  };
+
   // The expected return type of the request.  Options are:
   // json | stream | blob | arraybuffer | text
   // Defaults to `json`.

src/common.ts

@@ -43,6 +43,11 @@ export interface GaxiosResponse<T = any> {
  * Request options that are used to form the request.
  */
 export interface GaxiosOptions {
+  /**
+   * Optional method to override making the actual HTTP request. Useful
+   * for writing tests.
+   */
+  adapter?: <T = any>(options: GaxiosOptions) => GaxiosPromise<T>;
   url?: string;
   baseUrl?: string;  // deprecated
   baseURL?: string;

src/gaxios.ts

@@ -59,15 +59,20 @@ export class Gaxios {
   async request<T = any>(opts: GaxiosOptions = {}): GaxiosPromise<T> {
     opts = this.validateOpts(opts);
     try {
-      const res = await fetch(opts.url!, opts);
-      const data = await this.getResponseData(opts, res);
-      const translatedResponse = this.translateResponse(opts, res, data);
-      if (!opts.validateStatus!(res.status)) {
+      let translatedResponse: GaxiosResponse<T>;
+      if (opts.adapter) {
+        translatedResponse = await opts.adapter<T>(opts);
+      } else {
+        const res = await fetch(opts.url!, opts);
+        const data = await this.getResponseData(opts, res);
+        translatedResponse = this.translateResponse<T>(opts, res, data);
+      }
+      if (!opts.validateStatus!(translatedResponse.status)) {
         throw new GaxiosError<T>(
-            `Request failed with status code ${res.status}`, opts,
-            translatedResponse);
+            `Request failed with status code ${translatedResponse.status}`,
+            opts, translatedResponse);
       }
-      return this.translateResponse<T>(opts, res, data);
+      return translatedResponse;
     } catch (e) {
       const err = e as GaxiosError;
       err.config = opts;

test/test.getch.ts

@@ -18,7 +18,7 @@ import * as stream from 'stream';
 const assertRejects = require('assert-rejects');
 // tslint:disable-next-line variable-name
 const HttpsProxyAgent = require('https-proxy-agent');
-import {Gaxios, GaxiosError, request, GaxiosOptions} from '../src';
+import {Gaxios, GaxiosError, request, GaxiosOptions, GaxiosResponse} from '../src';
 import * as qs from 'querystring';
 import * as fs from 'fs';
 import {Blob} from 'node-fetch';
@@ -90,6 +90,21 @@ describe('🥁 configuration options', () => {
     scope.done();
   });
 
+  it('should allow overriding the adapter', async () => {
+    const response: GaxiosResponse = {
+      data: {hello: '🌎'},
+      config: {},
+      status: 200,
+      statusText: 'OK',
+      headers: {}
+    };
+    const adapter = (options: GaxiosOptions) => {
+      return Promise.resolve(response);
+    };
+    const res = await request({url, adapter});
+    assert.strictEqual(response, res);
+  });
+
   it('should encode query string parameters', async () => {
     const opts = {url, params: {james: 'kirk', montgomery: 'scott'}};
     const path = '/?james=kirk&montgomery=scott';