Firebase - Unable to serve local function after upgrading to 6.9.0 - firebase

Question

After upgrading firebase-tools from 6.8.0 to 6.9.0 my local function stopped working. I get below error message when calling it from my application:
λ firebase.cmd serve --only functions:upload
+ functions: Using node#12 from host.
+ functions: Emulator running at http://localhost:5001
i functions: Beginning execution of "upload"
! Error: Cannot find module 'package.json'
Require stack:
- C:\Users\MyLocalUsername\AppData\Roaming\npm\node_modules\firebase-tools\lib\emulator\functionsEmulatorRuntime.js
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:610:15)
at Function.Module._load (internal/modules/cjs/loader.js:526:27)
at Module.require (internal/modules/cjs/loader.js:666:19)
at require (internal/modules/cjs/helpers.js:16:16)
at verifyDeveloperNodeModules (C:\Users\MyLocalUsername\AppData\Roaming\npm\node_modules\firebase-tools\lib\emulator\functionsEmulatorRuntime.js:125:32)
at C:\Users\MyLocalUsername\AppData\Roaming\npm\node_modules\firebase-tools\lib\emulator\functionsEmulatorRuntime.js:457:26
at Generator.next (<anonymous>)
at C:\Users\MyLocalUsername\AppData\Roaming\npm\node_modules\firebase-tools\lib\emulator\functionsEmulatorRuntime.js:7:71
at new Promise (<anonymous>)
at __awaiter (C:\Users\MyLocalUsername\AppData\Roaming\npm\node_modules\firebase-tools\lib\emulator\functionsEmulatorRuntime.js:3:12)
! Your function was killed because it raised an unhandled error.
I have reinstalled node and npm entierly (including deleting %appdata% files), deleted all node_module files and reinstalled everything with npm ci but problem remains.
firebase.cmd is version 6.0.0
How do I continue? I could serve the very same function before upgrading, but now even if trying to downgrade using npm i firebase-tools#6.8.0 problem remains.
The function right now:
const functions = require('firebase-functions');
exports.upload = functions.https.onRequest((req, res) => {
console.log('Upload initiated')
return null;
});

Answer 1

I had the same problem after upgrading from firebase-tools 6.7.2 to 6.9.0
These steps worked for me to roll back to a previous version on Windows 10:
Uninstall the functions-emulator
Uninstall firebase-tools
Remove the functions-emulator config <== This is the step I didn't know about
Re-install a previous version of firebase-tools (6.7.2 or 6.8.0)
Detailed steps:
Switch nodejs version if you have multiple. I removed the functions-emulator and firebase-tools from all versions. Uninstalling needs to be done for each version separately.
nvm use 8.16.0
Uninstall the functions-emulator. More info: https://github.com/GoogleCloudPlatform/cloud-functions-emulator/wiki/Troubleshooting
npm uninstall -g #google-cloud/functions-emulator
Uninstall firebase-tools
npm uninstall -g firebase-tools
Delete the functions-emulator configuration folder found at 'C:\Users\yourusername\.config\configstore#google-cloud\functions-emulator'
Install a previous version of firebase-tools. Versions are listed at https://www.npmjs.com/package/firebase-tools
npm install -g firebase-tools#6.8.0
I believe you may only be able to use the functions-emulator with one nodejs version so if you install it with 8.16.0 then make sure you've switched to that version with '> nvm use 8.16.0' before you start testing cloud functions locally
Login to firebase
firebase login
In your project directory update the functions and admin packages
npm install firebase-functions#latest firebase-admin#latest --save
Start testing locally
firebase functions:shell
Or use
firebase serve
Note: Calling the functions-emulator directly with 'firebase emulators:start' won't work.
Follow this issue on github for updates: https://github.com/firebase/firebase-tools/issues/1258