quickscript: Like pressing Enter, but keeps the comments at the end of the line

new-line-keep-comments.rkt

#lang racket/base

(require quickscript
         racket/list
         racket/class
         racket/gui/event)

(script-help-string "Like pressing Enter, but keeps the comments at the end of the line")

;;; Author: Laurent Orseau <laurent.orseau@gmail.com>
;;; License: [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0) or
;;;          [MIT license](http://opensource.org/licenses/MIT) at your option.

;; Like pressing Enter, except that the comments at the end of the line
;; are not moved to the next line. Example, where | is the cursor:
;; (a b c |d) ; some comments
;; becomes
;; (a b c ; some comments
;;    d)
;; The whitespaces between c and | are deleted, while the whitespaces before the comments are moved
;; with the comments.
(define-script new-line-keep-comments
  #:label "new-line-keep-comments"
  #:shortcut #\return
  #:shortcut-prefix (ctl)
  (λ (selection #:editor ed)
    (send ed begin-edit-sequence)
    (define kmp (send ed get-keymap))
    (send kmp call-function "do-return" ed (new event%) #t)
    
    (define start (send ed get-start-position))
    (define line (send ed position-line start))
    (define end (send ed line-end-position line))
    (define txt (send ed get-text start end))
    (define m (regexp-match-positions #px"\\s*;.*$" txt))
    (when m
      (define pos (send ed get-start-position))
      (define start-comment (car (first m)))
      (define end-comment (cdr (first m)))
      (define comment (substring txt start-comment end-comment))
      (send ed delete (+ start start-comment) end) ; remove the comment
      (send ed set-position (send ed line-end-position (- line 1)))
      (send ed insert comment)
      (send ed set-position (+ pos (string-length comment))))
    (send ed end-edit-sequence)    
    #f))

(module url2script-info racket/base
  (provide filename url)
  (define filename "new-line-keep-comments.rkt")
  (define url "https://gist.github.com/Metaxal/0b1dd0176f9d4700e68a14eba1ceff2a"))