indent cl-loop to respect `if else` statements

Question

I have a hard time writing and reading cl-loops with they way they're indented by default as I can't easily tell what the control flow is:

(cl-loop for x below 10
         if (cl-oddp x)
         collect x into odds
         and if (memq x funny-numbers) return (cdr it) end
         else
         collect x into evens
         finally return (vector odds evens))

I'd like it to be indented like how it's shown in its documentation:

(cl-loop for x below 10
         if (cl-oddp x)
           collect x into odds
           and if (memq x funny-numbers) return (cdr it) end
         else
           collect x into evens
         finally return (vector odds evens))

I know this has to do with Indenting Macros manual page. And possibly this question on indenting a common lisp loop in emacs. Additionally, I've looked at a post on irreal and this question on the indentation of lisp forms.

The general idea I got from reading is to use (declare (indent n)) where n is an integer. I see this works for simple examples. However, how I want the cl-loop to be indented seems too complex for this. I need to tell emacs to recognize the specific if else keywords in the cl-loop.

I am confused as I don't see a clear way to properly indent cl-loop. Any ideas?

Answer 1

It seems that you can achieve your desired indentation style by doing

(setq lisp-indent-function 'common-lisp-indent-function)