Functions Framework prevents developers from handling invalid params

https://github.com/firebase/firebase-tools/issues/3891 seems to have a root cause in the functions framework.

To reproduce without Firebase:

const express = require('express');
const app = express();

app.get('/404', (req, res) => res.send('failed to work'));
app.get('**', (req, res) => res.send('working'));
app.use((err, req, res, next) => res.redirect('/404'));

module.exports.app = app;

if (require.main == module) {
  app.listen(8080);
}

If you run the file locally (no functions framework) and curl http://localhost:8080/%CO the user is redirected to http://localhost:8080/404.

If you deploy the function and CURL the repo (temporarily) at https://us-central1-inlined-junkdrawer.cloudfunctions.net/param-encoding/%C0, the functions framework rejects the request before it ever hits customer code with Bad Request

[devlucem]

Thanks for your response @grant.

The middleware solution you offered is not supported and cannot be a workaround as the URL is checked before it gets to any cloud function. @inlined code shows the middleware sample.

[grant]

Thanks.

What would you like the dev experience to be ideally? Expected behavior? Can you write that out?

I’m hearing you’d like to still invoke the function, but the server cannot accept a bad request. An error handler? Express sets up the router and processes params a bit out of our control.