Can I block vim from saving a file that isn't validated using an outside tool?

Question

I'm trying to find out if it's possible to make the write ":w" command perform a forced validation for certain file types.

My use case is that I want to prevent small typos and idention errors in python source code. So VIM should not even allow me to save a file with errors.

I can run "python -m py_compile filename" on a file to see if it compiles. This command returns nothing, if all is well, otherwise and error message like "Sorry: IndentationError: expected an indented block (hello.py, line 2)" Alas this requires me to save the file "filename, which I only want done if it passes.

So I'd need to automate these steps:

• save the current file with a temporary filename, like filename.insert_uuid_here.py
• run "python -m py_compile filename.insert_uuid_here.py

on success:

• remove both the filename.insert_uuid_here.py and the __python_cache__/filename.insert_uuid_here.py file.

• allow save

on fail:

• remove the filename.insert_uuid_here.py

• display error from compile attempt

Is this something, that's possible?

How could I link this to any ":w" attempt to write a python file?

Answer 1

You can use ALE to asynchronously lint (i.e. check for style/syntax errors) while you type. This will not prevent vim from saving the buffer when you instruct it to do so but that might be what actually you need/want.