Steps to replicate the issue (include links if applicable):
Go to the Edit function page of an existing function [1].
Start to delete the input type.
[1]
What happens?:
When you delete one character the whole input clears.
The 'Publish' button remains active.
What should have happened instead?:
You should be able to delete letter by letter (like the output box).
As soon as there is not a valid input, the 'Publish' button should become disabled (like it does for the output box).
Software version (skip for WMF-hosted wikis like Wikipedia):
Other information (browser name/version, screenshots, etc.):