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;;; shorthands.el --- Read code considering Elisp shorthands -*- lexical-binding: t; -*-
;; Copyright (C) 2021-2024 Free Software Foundation, Inc.
;; Author: João Távora <joaotavora@gmail.com>
;; Keywords: lisp
;; Package: emacs
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Basic helpers for loading files with Shorthands.
;;; Code:
(require 'files)
(require 'mule)
(eval-when-compile (require 'cl-lib))
(defun hack-read-symbol-shorthands ()
"Compute `read-symbol-shorthands' from Local Variables section."
;; FIXME: relies on the `hack-local-variables--find-variables'
;; detail of files.el. That function should be exported,
;; possibly be refactored into two parts, since we're only
;; interested in basic "Local Variables" parsing.
(alist-get 'read-symbol-shorthands (hack-local-variables--find-variables)))
(setq hack-read-symbol-shorthands-function #'hack-read-symbol-shorthands)
;; FIXME: move this all to progmodes/elisp-mode.el? OTOH it'd make
;; more sense there, OTOH all the elisp font-lock stuff is actually in
;; lisp/emacs-lisp/lisp-mode.el, which isn't right either. So
;; shorthand font-locking logic is probably better here for now.
(defface elisp-shorthand-font-lock-face
'((t :inherit font-lock-keyword-face :foreground "cyan"))
"Face for highlighting shorthands in Emacs Lisp."
:version "28.1"
:group 'font-lock-faces)
(defun shorthands--mismatch-from-end (str1 str2)
"Tell index of first mismatch in STR1 and STR2, from end.
The index is a valid 0-based index on STR1. Returns nil if STR1
equals STR2. Return 0 if STR1 is a suffix of STR2."
(cl-loop with l1 = (length str1) with l2 = (length str2)
for i from 1
for i1 = (- l1 i) for i2 = (- l2 i)
while (eq (aref str1 i1) (aref str2 i2))
if (zerop i2) return (if (zerop i1) nil i1)
if (zerop i1) return 0
finally (return i1)))
(defun shorthands-font-lock-shorthands (limit)
(when read-symbol-shorthands
(while (re-search-forward
(concat "\\_<\\(" (rx lisp-mode-symbol) "\\)\\_>")
limit t)
(let* ((existing (get-text-property (match-beginning 1) 'face))
(probe (and (not (memq existing '(font-lock-comment-face
font-lock-string-face)))
(intern-soft (match-string 1))))
(sname (and probe (symbol-name probe)))
(mismatch (and sname (shorthands--mismatch-from-end
(match-string 1) sname)))
(guess (and mismatch (1+ mismatch))))
(when guess
(when (and (< guess (1- (length (match-string 1))))
;; In bug#67390 we allow other separators
(eq (char-syntax (aref (match-string 1) guess)) ?_))
(setq guess (1+ guess)))
(add-face-text-property (match-beginning 1)
(+ (match-beginning 1) guess)
'elisp-shorthand-font-lock-face))))))
(font-lock-add-keywords 'emacs-lisp-mode '((shorthands-font-lock-shorthands)) t)
;;; shorthands.el ends here
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