I'm trying to get company mode to automatically trigger the pop-up with a list of possible completion. Unless I'm doing this wrong this is not the default behaviour? Current I have to run M-x company-complete manually.

I am not interesting in binding it to a key. I want the idle-completion behaviour. I'm using this with rustic (rust-mode fork).

Steps to reproduce:

  • Start from fresh emacs
[ -e ~/.emacs.d ] && mv ~/.emacs.d ~/.emacs.d.bak
mkdir ~/.emacs.d && cat <<'EOT' > ~/.emacs.d/init.el
(setq package-archives '(("gnu" . "http://elpa.gnu.org/packages/")
                         ("marmalade" . "https://marmalade-repo.org/packages/")
                         ("melpa" . "http://melpa.org/packages/")))

(require 'package)
  • Start Emacs
  • Install packages (from MELPA): lsp-mode, company, rustic
  • Install rustup (instructions at https://rustup.rs )
  • Install additionnal components: rustup component add rls rustfmt rust-src
  • Create new test project: cargo new rtest
  • Add the following to init.el:
(defun my-rust-hook ()
  (require 'company)
  (setq company-minimum-prefix-length 2)
  (setq company-idle-delay 0)

  ;; conf 1
  ;(setq company-auto-complete nil)
  ;; conf 2
  (setq company-auto-complete t)
  (add-to-list 'company-auto-complete-chars (char-syntax ?:))

  (company-mode 1)

(eval-after-load 'rustic
     (require 'lsp)
     (when (not (require 'yasnippet nil 'no-err))
       (setq lsp-enable-snippet nil))
     (add-hook 'rustic-mode-hook 'my-rust-hook)))
  • Restart emacs
  • Open rtest/src/main.rs
  • Type:
use std::env;

fn main() {
    // place point here at the end
  • Type env:: and wait. Completion menu doesn't show up.
  • You can try conf 1 or 2 from the init.el but you will see same result.
  • Running M-x company-complete works and shows the menu but idling doesn't.

1 Answer 1


What is the value of company-begin-commands? It should include at least self-insert-command. Also, try changing company-idle-delay to a low value above zero.

The Rust setup I describe in my setting up Rust with Emacs guide comes with a repo that has a working auto completion config via company. When in doubt, compare with that.

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