fix: return error response if destination request fails (#85)

Author: danadajian

lambda/proxy.test.ts

@@ -220,4 +220,39 @@ describe('proxy', () => {
     expect(result).toEqual(expectedResponseObject);
     expect(axios.post).toHaveBeenCalled();
   });
+
+  it('should return error response from axios', async () => {
+    const axiosErrorResponse: AxiosResponse = {
+      status: 400,
+      data: {
+        some: 'error'
+      },
+      headers: {
+        response: 'headers'
+      },
+      statusText: 'bad request',
+      config: {
+        headers: {} as AxiosRequestHeaders
+      }
+    };
+    (axios.post as jest.Mock).mockRejectedValue({ response: axiosErrorResponse });
+
+    process.env.ENTERPRISE_MANAGED_USER_SUFFIX = 'suffix';
+    const destinationUrl = 'https://approved.host/github-webhook/';
+    const endpointId = encodeURIComponent(destinationUrl);
+    const event: APIGatewayProxyWithLambdaAuthorizerEvent<any> = {
+      ...baseEvent,
+      body: JSON.stringify(VALID_PUSH_PAYLOAD_USER_REPO),
+      pathParameters: {
+        endpointId
+      }
+    };
+    const result = await handler(event);
+    expect(result).toEqual({
+      statusCode: 400,
+      body: '{"some":"error"}',
+      headers: { response: 'headers' }
+    });
+    expect(axios.post).toHaveBeenCalled();
+  });
 });

lambda/proxy.ts

@@ -11,7 +11,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import axios from 'axios';
+import axios, { AxiosError, AxiosResponse } from 'axios';
 import { APIGatewayProxyWithLambdaAuthorizerEvent } from 'aws-lambda';
 import { requestPayloadIsValid } from './request-payload-is-valid';
 import { destinationHostIsAllowed } from './destination-host-is-allowed';
@@ -47,10 +47,18 @@ export async function handler(event: APIGatewayProxyWithLambdaAuthorizerEvent<an
       data,
       headers: responseHeaders
     } = await axios.post(url, body, { headers, httpsAgent: getHttpsAgent() });
+    console.log('Request was forwarded successfully!');
     console.log('result', JSON.stringify({ statusCode, body: data, headers: responseHeaders }));
     return { statusCode, body: JSON.stringify(data), headers: responseHeaders };
-  } catch (e) {
-    console.error(e);
+  } catch (error) {
+    if (typeof error === 'object' && error && 'response' in error) {
+      console.log('Request was forwarded but got an error response.');
+      const { status: statusCode, data, headers: responseHeaders } = error.response as AxiosResponse;
+      console.log('result', JSON.stringify({ statusCode, body: data, headers: responseHeaders }));
+      return { statusCode, body: JSON.stringify(data), headers: responseHeaders };
+    }
+
+    console.error('An unknown error occurred.', error);
     return { statusCode: 500, body: 'Internal server error' };
   }
 }