fix(server): disable cache in live mode & fix missing function

When live mode is enabled there's now an explicit HTTP Header set to disable caching. Additionally
it will now throw an error message if no "handler" function was found

fix #35

Author: dkundel

package-lock.json

@@ -60,6 +60,7 @@
     "lodash.startcase": "^4.4.0",
     "log-symbols": "^2.2.0",
     "ngrok": "^3.0.1",
+    "nocache": "^2.1.0",
     "ora": "^3.3.1",
     "pkg-install": "^1.0.0",
     "prompts": "^2.0.4",

package.json

@@ -7,6 +7,7 @@ import express, {
   Request as ExpressRequest,
   Response as ExpressResponse,
 } from 'express';
+import nocache from 'nocache';
 import { StartCliConfig } from './cli/config';
 import { createLogger } from './internal/request-logger';
 import { setRoutes } from './internal/route-cache';
@@ -58,6 +59,10 @@ export async function createServer(
     app.use(createLogger(config));
   }
 
+  if (config.live) {
+    app.use(nocache());
+  }
+
   if (config.legacyMode) {
     process.env.TWILIO_FUNCTIONS_LEGACY_MODE = config.legacyMode
       ? 'true'
@@ -92,6 +97,13 @@ export async function createServer(
 
           log('Load & route to function at "%s"', functionPath);
           const twilioFunction = loadTwilioFunction(functionPath, config);
+          if (typeof twilioFunction !== 'function') {
+            return res
+              .status(404)
+              .send(
+                `Could not find a "handler" function in file ${functionPath}`
+              );
+          }
           functionToRoute(twilioFunction, config)(req, res, next);
         } catch (err) {
           log('Failed to retrieve function. %O', err);