fix: translate GaxiosError message to object regardless of return type (return data as default)

src/common.ts

@@ -28,6 +28,7 @@ export class GaxiosError<T = any> extends Error {
     super(message);
     this.response = response;
     this.config = options;
+    this.response.data = translateData(options.responseType, response.data);
     this.code = response.status.toString();
   }
 }
@@ -202,3 +203,18 @@ export interface FetchHeaders {
     thisArg?: any
   ): void;
 }
+
+function translateData(responseType: string | undefined, data: any) {
+  switch (responseType) {
+    case 'stream':
+      return data;
+    case 'json':
+      return JSON.parse(JSON.stringify(data));
+    case 'arraybuffer':
+      return JSON.parse(Buffer.from(data).toString('utf8'));
+    case 'blob':
+      return JSON.parse(data.text());
+    default:
+      return data;
+  }
+}

src/gaxios.ts

@@ -28,6 +28,7 @@ import {
   Headers,
 } from './common';
 import {getRetryConfig} from './retry';
+import {Stream} from 'stream';
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
@@ -155,6 +156,16 @@ export class Gaxios {
         translatedResponse = await this._defaultAdapter(opts);
       }
       if (!opts.validateStatus!(translatedResponse.status)) {
+        if (opts.responseType === 'stream') {
+          let response = '';
+          await new Promise(resolve => {
+            (translatedResponse.data as Stream).on('data', chunk => {
+              response += chunk;
+            });
+            (translatedResponse.data as Stream).on('end', resolve);
+          });
+          translatedResponse.data = response as T;
+        }
         throw new GaxiosError<T>(
           `Request failed with status code ${translatedResponse.status}`,
           opts,

test/test.getch.ts

@@ -56,6 +56,49 @@ describe('🚙 error handling', () => {
       return err.code === '500';
     });
   });
+
+  it('should throw the error as a GaxiosError object, regardless of Content-Type header', async () => {
+    const body = {
+      error: {
+        code: 404,
+        message: 'File not found',
+      },
+    };
+    const scope = nock(url).get('/').reply(404, body);
+    await assert.rejects(
+      request<JSON>({url, responseType: 'json'}),
+      (err: GaxiosError) => {
+        scope.done();
+        return (
+          err.code === '404' &&
+          err.message === 'Request failed with status code 404' &&
+          err.response?.data.error.message === 'File not found'
+        );
+      }
+    );
+  });
+
+  it('should throw the error as a GaxiosError object (with the message as a string), even if the request type is requested as an arraybuffer', async () => {
+    const body = {
+      error: {
+        code: 404,
+        message: 'File not found',
+      },
+    };
+    const scope = nock(url).get('/').reply(404, body);
+
+    await assert.rejects(
+      request<ArrayBuffer>({url, responseType: 'arraybuffer'}),
+      (err: GaxiosError) => {
+        scope.done();
+        return (
+          err.code === '404' &&
+          err.message === 'Request failed with status code 404' &&
+          err.response?.data.error.message === 'File not found'
+        );
+      }
+    );
+  });
 });
 
 describe('🥁 configuration options', () => {