apollo-datasource-rest: Dont' parse as json when status code is 204 No Content

packages/apollo-datasource-rest/src/RESTDataSource.ts

@@ -104,6 +104,9 @@ export abstract class RESTDataSource<TContext = any> extends DataSource {
   protected parseBody(response: Response): Promise<object | string> {
     const contentType = response.headers.get('Content-Type');
     if (
+      // As one might expect, a "204 No Content" is empty! This means there
+      // isn't enough to `JSON.parse`, and trying will result in an error.
+      response.status !== 204 &&
       contentType &&
       (contentType.startsWith('application/json') ||
         contentType.startsWith('application/hal+json'))

packages/apollo-datasource-rest/src/__tests__/RESTDataSource.test.ts

@@ -473,6 +473,24 @@ describe('RESTDataSource', () => {
 
       expect(data).toEqual('bar');
     });
+
+    it('returns data as a string when response status code is 204 no content', async () => {
+      const dataSource = new class extends RESTDataSource {
+        baseURL = 'https://api.example.com';
+
+        getFoo() {
+          return this.get('');
+        }
+      }();
+
+      dataSource.httpCache = httpCache;
+
+      fetch.mockResponseOnce('', { 'Content-Type': 'application/json' }, 204);
+
+      const data = await dataSource.getFoo();
+
+      expect(data).toEqual('');
+    });
   });
 
   describe('memoization', () => {