emacs philosophy: add dwim behavior when pressing Enter

Question

I recently added a modification to my Enter keybinding based on an answer (if you can't see it, this is a link) on this SE. It was good and I liked it. So of course...

Now I want to add MORE dwim behavior. Specifically, while programming, if I'm typing a comment, I'd like to press the Enter key and the next line automatically also be a comment. E.g. in Ruby, if I have # blah blah| where | is the cursor, I want to press Enter and see

# blah blah
# |

So the question - what is preferred / philosophically correct with emacs?

Do I:

1. Expand my enter-key-dwim function to just check for more things?
2. Do I switch to two small functions that work as a local-buffer post-command-hook and only run if the last command was the Enter key?
3. Put an advice around the Enter key behavior?
4. Something else?

One comment says that I generally want to avoid post-command-hook because it gets run after every keystroke as well, which seems to be a vote against option 2.

Answer 1

Just make your own hook! Here's an example that does what the answer you linked does: add an extra newline if you are between brackets. You can add other hooks without changing newline-dwim.

(defun newline-dwim ()
  (interactive)
  (run-hooks 'newline-hooks))

(defun basic-newline ()
  (newline)
  (indent-for-tab-command))

(defun extra-newline-inside-braces ()
  (when (and (eq ?\( (char-syntax (char-before)))
             (eq ?\) (char-syntax (char-after))))
    (save-excursion (basic-newline))))

(add-hook 'newline-hooks #'basic-newline)
(add-hook 'newline-hooks #'extra-newline-inside-braces)

Answer 2

Behavior of several commands is customizable. The features in question often are called "electric". python-mode.el would provide that comment-insert when py-electric-comment-p is set to t.

Answer 3

Well, since I already had a tool that went most of the way (my current enter-key-dwim) and emacs already has a tool that did what I want, I sidestepped the philosophical question and did the pragmatic thing; I replaced "newline and indenting" with "newline and indenting also with special behavior if inside a comment" (indent-new-comment-line).

This is acceptable for me right now. I don't mind having to press C-j for a non-comment-newline ... Yet.