Add debug feature to always enable cors for emulated v2 https functions

CHANGELOG.md

@@ -0,0 +1 @@
+- Add debug feature to enable cors option for v2 onRequest and onCall handlers. (#1099)

spec/v2/providers/https.spec.ts

@@ -20,8 +20,10 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+import * as sinon from 'sinon';
 import { expect } from 'chai';
 
+import * as debug from '../../../src/common/debug';
 import * as options from '../../../src/v2/options';
 import * as https from '../../../src/v2/providers/https';
 import {
@@ -166,7 +168,7 @@ describe('onRequest', () => {
       {
         'Access-Control-Request-Method': 'POST',
         'Access-Control-Request-Headers': 'origin',
-        Origin: 'example.com',
+        origin: 'example.com',
       }
     );
     req.method = 'OPTIONS';
@@ -181,6 +183,41 @@ describe('onRequest', () => {
       Vary: 'Origin, Access-Control-Request-Headers',
     });
   });
+
+  it('should add CORS headers if debug feature is enabled', async () => {
+    sinon
+      .stub(debug, 'isDebugFeatureEnabled')
+      .withArgs('enableCors')
+      .returns(true);
+
+    const func = https.onRequest((req, res) => {
+      throw new Error('Should not reach here for OPTIONS preflight');
+    });
+
+    const req = new MockRequest(
+      {
+        data: {},
+      },
+      {
+        'Access-Control-Request-Method': 'POST',
+        'Access-Control-Request-Headers': 'origin',
+        origin: 'localhost',
+      }
+    );
+    req.method = 'OPTIONS';
+
+    const resp = await runHandler(func, req as any);
+    expect(resp.status).to.equal(204);
+    expect(resp.body).to.be.undefined;
+    expect(resp.headers).to.deep.equal({
+      'Access-Control-Allow-Methods': 'GET,HEAD,PUT,PATCH,POST,DELETE',
+      'Access-Control-Allow-Origin': 'localhost',
+      'Content-Length': '0',
+      Vary: 'Origin, Access-Control-Request-Headers',
+    });
+
+    sinon.restore();
+  });
 });
 
 describe('onCall', () => {
@@ -317,7 +354,7 @@ describe('onCall', () => {
       {
         'Access-Control-Request-Method': 'POST',
         'Access-Control-Request-Headers': 'origin',
-        Origin: 'example.com',
+        origin: 'example.com',
       }
     );
     req.method = 'OPTIONS';
@@ -333,6 +370,41 @@ describe('onCall', () => {
     });
   });
 
+  it('overrides CORS headers if debug feature is enabled', async () => {
+    sinon
+      .stub(debug, 'isDebugFeatureEnabled')
+      .withArgs('enableCors')
+      .returns(true);
+
+    const func = https.onCall({ cors: 'example.com' }, (request) => {
+      throw new Error('Should not reach here for OPTIONS preflight');
+    });
+    const req = new MockRequest(
+      {
+        data: {},
+      },
+      {
+        'Access-Control-Request-Method': 'POST',
+        'Access-Control-Request-Headers': 'origin',
+        origin: 'localhost',
+      }
+    );
+    req.method = 'OPTIONS';
+
+    const response = await runHandler(func, req as any);
+
+    expect(response.status).to.equal(204);
+    expect(response.body).to.be.undefined;
+    expect(response.headers).to.deep.equal({
+      'Access-Control-Allow-Methods': 'POST',
+      'Access-Control-Allow-Origin': 'localhost',
+      'Content-Length': '0',
+      Vary: 'Origin, Access-Control-Request-Headers',
+    });
+
+    sinon.restore();
+  });
+
   it('adds CORS headers', async () => {
     const func = https.onCall((request) => 42);
     const req = new MockRequest(

src/common/debug.ts

@@ -25,6 +25,7 @@ const debugMode = process.env.FIREBASE_DEBUG_MODE === 'true';
 
 interface DebugFeatures {
   skipTokenVerification?: boolean;
+  enableCors?: boolean;
 }
 
 function loadDebugFeatures(): DebugFeatures {

src/v2/providers/https.ts

@@ -34,6 +34,7 @@ import {
 import { ManifestEndpoint } from '../../runtime/manifest';
 import * as options from '../options';
 import { GlobalOptions, SupportedRegion } from '../options';
+import { isDebugFeatureEnabled } from '../../common/debug';
 
 export { Request, CallableRequest, FunctionsErrorCode, HttpsError };
 
@@ -89,12 +90,13 @@ export function onRequest(
     opts = optsOrHandler as HttpsOptions;
   }
 
-  if ('cors' in opts) {
+  if (isDebugFeatureEnabled('enableCors') || 'cors' in opts) {
+    const origin = isDebugFeatureEnabled('enableCors') ? true : opts.cors;
     const userProvidedHandler = handler;
     handler = (req: Request, res: express.Response): void | Promise<void> => {
       return new Promise((resolve) => {
         res.on('finish', resolve);
-        cors({ origin: opts.cors })(req, res, () => {
+        cors({ origin })(req, res, () => {
           resolve(userProvidedHandler(req, res));
         });
       });
@@ -179,7 +181,11 @@ export function onCall<T = any, Return = any | Promise<any>>(
     opts = optsOrHandler as HttpsOptions;
   }
 
-  const origin = 'cors' in opts ? opts.cors : true;
+  const origin = isDebugFeatureEnabled('enableCors')
+    ? true
+    : 'cors' in opts
+    ? opts.cors
+    : true;
 
   // onCallHandler sniffs the function length to determine which API to present.
   // fix the length to prevent api versions from being mismatched.