fix!: examine response content-type if no contentType is set (#535)

* fix: examine response content-type if no contentType is set

* pin compodoc dep to 1.1.19

* update README with unknown responseType

---------

Co-authored-by: sofisl <55454395+sofisl@users.noreply.github.com>

README.md

@@ -101,9 +101,9 @@ over other authentication methods, i.e., application default credentials.
   };
 
   // The expected return type of the request.  Options are:
-  // json | stream | blob | arraybuffer | text
-  // Defaults to `json`.
-  responseType: 'json',
+  // json | stream | blob | arraybuffer | text | unknown
+  // Defaults to `unknown`.
+  responseType: 'unknown',
 
   // The node.js http agent to use for the request.
   agent: someHttpsAgent,

src/common.ts

@@ -95,7 +95,13 @@ export interface GaxiosOptions {
    * @deprecated ignored
    */
   onUploadProgress?: (progressEvent: any) => void;
-  responseType?: 'arraybuffer' | 'blob' | 'json' | 'text' | 'stream';
+  responseType?:
+    | 'arraybuffer'
+    | 'blob'
+    | 'json'
+    | 'text'
+    | 'stream'
+    | 'unknown';
   agent?: Agent | ((parsedUrl: URL) => Agent);
   validateStatus?: (status: number) => boolean;
   retryConfig?: RetryConfig;

src/gaxios.ts

@@ -207,7 +207,7 @@ export class Gaxios {
       case 'blob':
         return res.blob();
       default:
-        return res.text();
+        return this.getResponseDataFromContentType(res);
     }
   }
 
@@ -282,7 +282,7 @@ export class Gaxios {
     }
 
     opts.validateStatus = opts.validateStatus || this.validateStatus;
-    opts.responseType = opts.responseType || 'json';
+    opts.responseType = opts.responseType || 'unknown';
     if (!opts.headers['Accept'] && opts.responseType === 'json') {
       opts.headers['Accept'] = 'application/json';
     }
@@ -364,4 +364,31 @@ export class Gaxios {
       },
     };
   }
+
+  /**
+   * Attempts to parse a response by looking at the Content-Type header.
+   * @param {FetchResponse} response the HTTP response.
+   * @returns {Promise<any>} a promise that resolves to the response data.
+   */
+  private getResponseDataFromContentType(
+    response: FetchResponse
+  ): Promise<any> {
+    let contentType = response.headers.get('Content-Type');
+    if (contentType === null) {
+      // Maintain existing functionality by calling text()
+      return response.text();
+    }
+    contentType = contentType.toLowerCase();
+    if (contentType.includes('application/json')) {
+      return response.json();
+    } else if (
+      contentType.includes('text/plain') ||
+      contentType.includes('text/html')
+    ) {
+      return response.text();
+    } else {
+      // If the content type is something not easily handled, just return the raw data (blob)
+      return response.blob();
+    }
+  }
 }

test/test.getch.ts

@@ -290,7 +290,7 @@ describe('🥁 configuration options', () => {
       .matchHeader('accept', 'application/json')
       .get('/')
       .reply(200, {});
-    const res = await request({url});
+    const res = await request({url, responseType: 'json'});
     scope.done();
     assert.deepStrictEqual(res.data, {});
   });
@@ -575,6 +575,39 @@ describe('🎏 data handling', () => {
     assert.ok(res.data);
     assert.strictEqual(res.statusText, 'OK');
   });
+
+  it('should return JSON when response Content-Type=application/json', async () => {
+    const body = {hello: 'world'};
+    const scope = nock(url)
+      .get('/')
+      .reply(200, body, {'Content-Type': 'application/json'});
+    const res = await request({url});
+    scope.done();
+    assert.ok(res.data);
+    assert.deepStrictEqual(res.data, body);
+  });
+
+  it('should return text when response Content-Type=text/plain', async () => {
+    const body = 'hello world';
+    const scope = nock(url)
+      .get('/')
+      .reply(200, body, {'Content-Type': 'text/plain'});
+    const res = await request({url});
+    scope.done();
+    assert.ok(res.data);
+    assert.deepStrictEqual(res.data, body);
+  });
+
+  it('should return raw data when Content-Type is unable to be parsed', async () => {
+    const body = Buffer.from('hello world', 'utf-8');
+    const scope = nock(url)
+      .get('/')
+      .reply(200, body, {'Content-Type': 'image/gif'});
+    const res = await request({url});
+    scope.done();
+    assert.ok(res.data);
+    assert.notEqual(res.data, body);
+  });
 });
 
 describe('🍂 defaults & instances', () => {