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Álvaro Ramírez
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Álvaro Ramírez

01 November 2017 Eshell pcomplete company completion

Howard Abrams's Introduction to eshell video prompted me to poke at eshell some more. This time, I got eshell context aware completion by glueing the excellent company and pcomplete packages.

company-pcomplete.png 

(require 'cl-lib)
(require 'company)
(require 'dash)
(require 'pcomplete)
(require 's)

(defun company-pcomplete--overlap-tail (a b)
  "When A is \"SomeDev\" and B is \"Developer\", return \"eloper\"."
  (let ((prefix a)
        (remaining nil))
    (while (and (not remaining) (> (length prefix) 0))
      (when (s-starts-with? prefix b)
        (setq remaining (substring b (length prefix))))
      (setq prefix (substring prefix 1)))
    remaining))

(defun company-pcomplete--candidates (prefix)
  "Get candidates for PREFIX company completion using `pcomplete'."
  ;; When prefix is: "~/Down" and completion is "Downloads", need
  ;; to find common string and join into "~/Downloads/".
  (-map (lambda (item)
          (if (s-starts-with? prefix item)
              item
            (concat prefix (company-pcomplete--overlap-tail prefix item))))
        (all-completions prefix (pcomplete-completions))))

(defun company-pcomplete (command &optional arg &rest ignored)
  "Complete using pcomplete. See `company''s COMMAND ARG and IGNORED for details."
  (interactive (list 'interactive))
  (case command
    (interactive (company-begin-backend 'company-pcomplete))
    (prefix (company-grab-symbol))
    (candidates
     (company-pcomplete--candidates arg))))

Don't forget to add company-pcomplete to company-backends, and if you want an explicit binding, use something like: 

(bind-key "<backtab>" #'company-complete eshell-mode-map)