A few notes on Elisp indentation

I sure do like to keep my Elisp code nice and indented. But sometimes the indentation engine just won't listen.

lisp-indent-function

By default, the indentation is handled as if:

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

At least in one case, it looks horrible:

(cl-labels ((square (x)
                    (* x x)))
  (mapcar #'square '(0 1 2 3 4 5)))
;; => (0 1 4 9 16 25)

That's why I have:

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

which leads to this indentation:

(cl-labels ((square (x)
              (* x x)))
  (mapcar #'square '(0 1 2 3 4 5)))
;; => (0 1 4 9 16 25)

Ah, much better. The indentation does change a bit in other places as a result of this. To my experience, it can be fixed on a case-by-case basis by declaring the indent level for the offending function or macro.

Declaring indent level

Here's how it looks like

(defmacro lispy-save-excursion (&rest body)
  "More intuitive (`save-excursion' BODY)."
  (declare (indent 0))
  `(let ((out (save-excursion
                ,@body)))
     (when (bolp)
       (back-to-indentation))
     out))

By default, functions behave as if their indent was declared to nil. Zero here means that we expect zero arguments on the same line, so that this indentation follows:

(lispy-save-excursion
  (lispy--out-forward arg)
  (backward-list)
  (indent-sexp))

The indentation above is just like the one that the original save-excursion has. Note that if I hadn't declared the indent, it would look like this:

(lispy-save-excursion
 (lispy--out-forward arg)
 (backward-list)
 (indent-sexp))

The impact is much larger for statements that require an indent of 1:

Compare the proper thing:

(lispy-dotimes arg
  (when (= (point) (point-max))
    (error "Reached end of buffer"))
  (forward-list))

to this horror:

(lispy-dotimes arg
               (when (= (point) (point-max))
                 (error "Reached end of buffer"))
               (forward-list))

Outro

I've shown two things you can try if you find your Elisp indentation annoying. If you know of more, let me know.