I experienced a bug where ng add @angular-fire followed by firebase init functions broke ng deploy due to a bug in firebase-tools.
Angular CLI:
8.3.19
Firebase:
>= 5.5.7 <8
AngularFire:
5.2.3
ng new
ng add @angular-fire
firebase init functions
ng deploy (should break)
* Output from ng deploy *

* After reinstalling firebase-tools with npm install --save-dev firebase-tools@latest *

ng deploy deploys the application to Firebase.
You get an error
TypeError: entry.message.split is not a function
The error is coming from firebase-tools. The bug has been fixed in v7.7.0
Link to the fix
TLDR; If you're getting this error, just run npm install --save-dev firebase-tools@latest
Also, you can observe the actual error message if you console log entry in node_modules/@angular-devkit/core/src/logger/logger.js Logger.next.

I've got firebase-tools 7.12.1, and this is still broken.
This just started happening for me too.
broken here too
Broken for me too with firebase-tools at 7.16.1
As a temporary fix it seems if you delete firebase.json and .firebaserc and then run ng add @angular/fire then it works again.
Most helpful comment
As a temporary fix it seems if you delete
firebase.jsonand.firebasercand then runng add @angular/firethen it works again.