Finding the place where auto-fill-mode is getting enabled and disabling it

Question

So, whenever I open a new buffer, auto-fill-mode is enabled. I have checked my configuration and have verified that I'm not enabling it in the init.el file. How do I find out from where it is getting enabled ?

Also, how do I disable it in a certain mode like html-mode. I tried some suggestions in this thread but this doesn't seem to work for me:

(remove-hook 'html-mode-hook 'turn-on-auto-fill)

Answer 1

What I usually do is look at the doc string first and search for "hook". This gives me html-mode-hook and the hooks of its parents. Search for "parent" and this gives me sgml-mode. Keep repeating. I end up with:

1. html-mode-hook
2. sgml-mode-hook
3. text-mode-hook

Still in the *Help* buffer, you can click on all of those and see what's there. In my case, I see turn-on-auto-fill on text-mode-hook. The solution was this:

(add-hook 'html-mode-hook 'turn-off-auto-fill)

Text Mode will have auto-fill enabled and HTML Mode will have auto-fill disabled. You could argue that I probably don't want SGML Mode to have auto-fill enabled, but since I don't use it, I don't care. :)

Looking at Doc Strings: If it's a function, use C-h f. If it's a variable, use C-h v. If you don't know what your major mode is, examine the variable major-mode using C-h v. This should tell you the major mode such as html-mode. This is a function, so you need to use C-h f.

Answer 2

You can get Emacs to show you a stack trace when the function is called, so that you can figure out what called it.

1. M-x debug-on-entry RET auto-fill-mode RET
2. trigger the issue
3. Check the stack trace. Depending on the details, the exact cause may not be 100% clear, but it should certainly give you a good idea of where to look next.
4. Use c to continue execution of the function, or q to quit the debugger.
5. M-x cancel-debug-on-entry RET RET

The documentation for the debugger is in the manual:

C-hig (elisp) Debugger RET

Be sure to read the "Debugger Commands" node.