Emacs – autocompletion in Emacs Lisp mode

emacs

Recently I've discovered M-x ielm (the Emacs self-REPL) and was pleasantly surprised that there's a working tab-completion in that mode. Say, I can start typing ecb-, then hit TAB and ielm will show me what functions are exposed by ECB. Very convenient for exploration!

However, when I start editing one of my *.el files (in Emacs Lisp major mode), TAB no longer works as autocomplete and performs indentation, which I find unfortunate.

I tried to figure out how autocompletion works within ielm in order to possibly transplant it into Emacs Lisp mode. However, apparently, autocompletion in ielm uses comint-dynamic-complete, which, as far as I understand, works only in comint-based buffers. I guess, this means that I'm out of luck here.

So, well, how do I enable autocompletion for Emacs Lisp?

Best Answer

In recent versions of Emacs, you can use a little-known piece of built-in functionality which enables TAB completion:

(setq tab-always-indent 'complete)
(add-to-list 'completion-styles 'initials t)

With this setup, TAB - which is usually bound to indent-for-tab-command - first tries to adjust the indentation according to the mode's settings, but if the indentation is already correct, completion is triggered. This is usually the desired behavior, and IMHO works better than third-party plugins like smart-tab.

Note, however, that in some modes, TAB is not bound to indent-for-tab-command, so further rebinding is necessary for those modes, e.g. with smart-tab. Also, when modes have "bounce indent" (e.g. python-mode), this technique will also not work.

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How to control how Emacs makes backup files

If you've ever been saved by an Emacs backup file, you probably want more of them, not less of them. It is annoying that they go in the same directory as the file you're editing, but that is easy to change. You can make all backup files go into a directory by putting something like the following in your .emacs.

(setq backup-directory-alist `(("." . "~/.saves")))

There are a number of arcane details associated with how Emacs might create your backup files. Should it rename the original and write out the edited buffer? What if the original is linked? In general, the safest but slowest bet is to always make backups by copying.

(setq backup-by-copying t)

If that's too slow for some reason you might also have a look at backup-by-copying-when-linked.

Since your backups are all in their own place now, you might want more of them, rather than less of them. Have a look at the Emacs documentation for these variables (with C-h v).

(setq delete-old-versions t
  kept-new-versions 6
  kept-old-versions 2
  version-control t)

Finally, if you absolutely must have no backup files:

(setq make-backup-files nil)

It makes me sick to think of it though.

Bash autocompletion in Emacs shell-mode

I know this question is three years old, but it's something that I've also been interested in solving. A Web search directed me to a piece of elisp that makes Emacs use bash for completion in shell mode. It works for me, in any case.

Check it out at https://github.com/szermatt/emacs-bash-completion .

Best Answer

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How to control how Emacs makes backup files

Bash autocompletion in Emacs shell-mode

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