I am an avid hippie-expand user but I find it annoying that it natively doesn't complete ruby symbols without the prefix. For example (cursor is |):

class ApplicationController < ActionController::Base
  before_action :some_action


  def some_a|


If I trigger hippie-expand here, it doesn't know that :some_action is also a completion option without the : prefix.

What is the cleanest way to extend hippie-expand (or perhaps dabbrev-expand) to do this?

  • 1
    Yeah, it annoys me as well. So far, though, the best idea I've got is to change the syntax of : in ruby-mode back to punctuation. It will require quite a few changes to the code, in different places.
    – Dmitry
    Jun 10, 2015 at 22:51

1 Answer 1


@Dmitry made a great point that hippie-expand will do what I'm desiring when : is considered a punctuation character.

It's obviously not ideal to just set (modify-syntax-entry ?: "." ruby-mode-syntax-table) in your init and call it a day, because then only some_action in :some_action is considered a symbol which would break expectations for other plugins. This seems ripe for re-defining with advice though.

Here's what I came up with:

(defun hippie-expand-ruby-symbols (orig-fun &rest args)
  (if (eq major-mode 'ruby-mode)
      (let ((table (make-syntax-table ruby-mode-syntax-table)))
        (modify-syntax-entry ?: "." table)
        (with-syntax-table table (apply orig-fun args)))
    (apply orig-fun args)))

(advice-add 'hippie-expand :around #'hippie-expand-ruby-symbols)

If hippie-expand is called when the major-mode is ruby-mode, define a cloned temporary syntax table where : is a punctuation character and call hippie-expand with it. Otherwise, just call hippie-expand as normal.

Any downside to this approach?

  • This is a pretty great approach, actually. Here's a possible tweak: instead of major-mode comparison, you should be able to call advice-add in ruby-mode-hook, if you replace 'hippy-expand with (local 'hippy-expand).
    – Dmitry
    Jun 11, 2015 at 19:52

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