UPDATE: This is now available on melpa.
Back in 2015, I bound the "<" key to a hydra for quickly inserting org blocks. The idea came from Oleg's post on org-mode block templates in Hydra. The suggested binding settled in my muscle memory without much effort.
Fast forward to Febrary 2019. I replaced the hydra with org-insert-structure-template when org-try-structure-completion was removed from org mode. No biggie, as I kept the same binding to "<" and hardly noticed the change.
Since my primary use-case for easy templates is inserting source blocks, I was keen to expedite choosing the source language as well as inserting the source block itself.
Writing a small company mode completion backend fits my primary use-case pretty well.
The company backend looks as follow (Warning: Snippet needs Org v9.2).
Note: This code is not up to date. Install via melpa or see its repository.
(require 'map)
(require 'org)
(require 'seq)
(defvar company-org-block-bol-p t "If t, detect completion when at
begining of line, otherwise detect completion anywhere.")
(defvar company-org--regexp "<\\([^ ]*\\)")
(defun company-org-block (command &optional arg &rest ignored)
"Complete org babel languages into source blocks."
(interactive (list 'interactive))
(cl-case command
(interactive (company-begin-backend 'company-org-block))
(prefix (when (derived-mode-p 'org-mode)
(company-org-block--grab-symbol-cons)))
(candidates (company-org-block--candidates arg))
(post-completion
(company-org-block--expand arg))))
(defun company-org-block--candidates (prefix)
"Return a list of org babel languages matching PREFIX."
(seq-filter (lambda (language)
(string-prefix-p prefix language))
;; Flatten `org-babel-load-languages' and
;; `org-structure-template-alist', join, and sort.
(seq-sort
#'string-lessp
(append
(mapcar #'prin1-to-string
(map-keys org-babel-load-languages))
(map-values org-structure-template-alist)))))
(defun company-org-block--template-p (template)
(seq-contains (map-values org-structure-template-alist)
template))
(defun company-org-block--expand (insertion)
"Replace INSERTION with actual source block."
(delete-region (point) (- (point) (1+ ;; Include "<" in length.
(length insertion))))
(if (company-org-block--template-p insertion)
(company-org-block--wrap-point insertion
;; May be multiple words.
;; Take the first one.
(nth 0 (split-string insertion)))
(company-org-block--wrap-point (format "src %s" insertion)
"src")))
(defun company-org-block--wrap-point (begin end)
"Wrap point with block using BEGIN and END. For example:
#+begin_BEGIN
|
#+end_END"
(insert (format "#+begin_%s\n" begin))
(insert (make-string org-edit-src-content-indentation ?\s))
;; Saving excursion restores point to location inside code block.
(save-excursion
(insert (format "\n#+end_%s" end))))
(defun company-org-block--grab-symbol-cons ()
"Return cons with symbol and t whenever prefix of < is found.
For example: \"<e\" -> (\"e\" . t)"
(when (looking-back (if company-org-block-bol-p
(concat "^" company-org--regexp)
company-org--regexp)
(line-beginning-position))
(cons (match-string-no-properties 1) t)))
To use, add the backend enable company-mode in org-mode:
(add-to-list 'company-backends 'company-org-block)
(company-mode +1)