feat: pass default adapter to adapter option

README.md

@@ -80,11 +80,14 @@ gaxios.request({url: '/data'}).then(...);
   timeout: 1000,
 
   // Optional method to override making the actual HTTP request. Useful
-  // for writing tests.
-  adapter?: (options) => {
-    return {
-      data: 'your data'
-    }
+  // for writing tests and instrumentation
+  adapter?: async (options, defaultAdapter) => {
+    const res = await defaultAdapter(options);
+    res.data = {
+      ...res.data,
+      extraProperty: 'your extra property',
+    };
+    return res;
   };
 
   // The expected return type of the request.  Options are:

browser-test/test.browser.ts

@@ -14,15 +14,9 @@
 import assert from 'assert';
 import {describe, it} from 'mocha';
 import {request} from '../src/index';
-import {PassThrough} from 'stream';
-import * as stream from 'stream';
 import * as uuid from 'uuid';
 const port = 7172; // should match the port defined in `webserver.ts`
 
-function isReadableStream(obj: stream.Readable | string) {
-  return obj instanceof stream.Readable && typeof obj._read === 'function';
-}
-
 describe('💻 browser tests', () => {
   it('should just work from browser', async () => {
     const result = await request({url: `http://localhost:${port}/path`});

package.json

@@ -40,6 +40,8 @@
   "license": "Apache-2.0",
   "devDependencies": {
     "@compodoc/compodoc": "^1.1.9",
+    "@microsoft/api-documenter": "^7.8.10",
+    "@microsoft/api-extractor": "^7.8.10",
     "@types/cors": "^2.8.6",
     "@types/execa": "^0.9.0",
     "@types/express": "^4.16.1",
@@ -55,6 +57,7 @@
     "@types/tmp": "0.2.0",
     "@types/uuid": "^8.0.0",
     "c8": "^7.0.0",
+    "chai": "^4.2.0",
     "codecov": "^3.2.0",
     "cors": "^2.8.5",
     "execa": "^4.0.0",
@@ -83,9 +86,7 @@
     "typescript": "^3.8.3",
     "uuid": "^8.0.0",
     "webpack": "^4.29.5",
-    "webpack-cli": "^3.2.3",
-    "@microsoft/api-documenter": "^7.8.10",
-    "@microsoft/api-extractor": "^7.8.10"
+    "webpack-cli": "^3.2.3"
   },
   "dependencies": {
     "abort-controller": "^3.0.0",

src/common.ts

@@ -59,7 +59,10 @@ export interface GaxiosOptions {
    * Optional method to override making the actual HTTP request. Useful
    * for writing tests.
    */
-  adapter?: <T = any>(options: GaxiosOptions) => GaxiosPromise<T>;
+  adapter?: <T = any>(
+    options: GaxiosOptions,
+    defaultAdapter: (options: GaxiosOptions) => GaxiosPromise<T>
+  ) => GaxiosPromise<T>;
   url?: string;
   baseUrl?: string; // deprecated
   baseURL?: string;

src/gaxios.ts

@@ -90,6 +90,14 @@ export class Gaxios {
     return this._request(opts);
   }
 
+  private async _defaultAdapter<T>(
+    opts: GaxiosOptions
+  ): Promise<GaxiosResponse<T>> {
+    const res = await fetch(opts.url!, opts);
+    const data = await this.getResponseData(opts, res);
+    return this.translateResponse<T>(opts, res, data);
+  }
+
   /**
    * Internal, retryable version of the `request` method.
    * @param opts Set of HTTP options that will be used for this HTTP request.
@@ -98,11 +106,12 @@ export class Gaxios {
     try {
       let translatedResponse: GaxiosResponse<T>;
       if (opts.adapter) {
-        translatedResponse = await opts.adapter<T>(opts);
+        translatedResponse = await opts.adapter<T>(
+          opts,
+          this._defaultAdapter.bind(this)
+        );
       } else {
-        const res = await fetch(opts.url!, opts);
-        const data = await this.getResponseData(opts, res);
-        translatedResponse = this.translateResponse<T>(opts, res, data);
+        translatedResponse = await this._defaultAdapter(opts);
       }
       if (!opts.validateStatus!(translatedResponse.status)) {
         throw new GaxiosError<T>(

system-test/fixtures/sample/webpack.config.js

@@ -32,6 +32,8 @@ module.exports = {
     child_process: 'empty',
     fs: 'empty',
     crypto: 'empty',
+    net: 'empty',
+    tls: 'empty',
   },
   module: {
     rules: [

test/test.getch.ts

@@ -131,6 +131,34 @@ describe('🥁 configuration options', () => {
     assert.strictEqual(response, res);
   });
 
+  it('should allow overriding the adapter with default adapter wrapper', async () => {
+    const body = {hello: '🌎'};
+    const extraProperty = '🦦';
+    const scope = nock(url).get('/').reply(200, body);
+    const timings: {duration: number}[] = [];
+    const res = await request({
+      url,
+      adapter: async (opts, defaultAdapter) => {
+        const begin = Date.now();
+        const res = await defaultAdapter(opts);
+        const end = Date.now();
+        res.data = {
+          ...res.data,
+          extraProperty,
+        };
+        timings.push({duration: end - begin});
+        return res;
+      },
+    });
+    scope.done();
+    assert.deepStrictEqual(res.data, {
+      ...body,
+      extraProperty,
+    });
+    assert(timings.length === 1);
+    assert(typeof timings[0].duration === 'number');
+  });
+
   it('should encode URL parameters', async () => {
     const path = '/?james=kirk&montgomery=scott';
     const opts = {url: `${url}${path}`};

webpack-tests.config.js

@@ -27,6 +27,8 @@ module.exports = {
     child_process: 'empty',
     fs: 'empty',
     crypto: 'empty',
+    net: 'empty',
+    tls: 'empty',
   },
   module: {
     rules: [

webpack.config.js

@@ -33,6 +33,8 @@ module.exports = {
     child_process: 'empty',
     fs: 'empty',
     crypto: 'empty',
+    net: 'empty',
+    tls: 'empty',
   },
   module: {
     rules: [