company doesn't pop up completion list automatically

Question

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)
(package-initialize)
EOT

• 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
  '(progn
     (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.

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.