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1 ;;; elec-pair.el --- Automatic parenthesis pairing -*- lexical-binding:t -*-
3 ;; Copyright (C) 2013-2014 Free Software Foundation, Inc.
5 ;; Author: João Távora <joaotavora@gmail.com>
7 ;; This file is part of GNU Emacs.
9 ;; GNU Emacs is free software: you can redistribute it and/or modify
10 ;; it under the terms of the GNU General Public License as published by
11 ;; the Free Software Foundation, either version 3 of the License, or
12 ;; (at your option) any later version.
14 ;; GNU Emacs is distributed in the hope that it will be useful,
15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 ;; GNU General Public License for more details.
19 ;; You should have received a copy of the GNU General Public License
20 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
22 ;;; Commentary:
24 ;;; Code:
26 (require 'electric)
28 ;;; Electric pairing.
30 (defcustom electric-pair-pairs
31 '((?\" . ?\"))
32 "Alist of pairs that should be used regardless of major mode.
34 Pairs of delimiters in this list are a fallback in case they have
35 no syntax relevant to `electric-pair-mode' in the mode's syntax
36 table.
38 See also the variable `electric-pair-text-pairs'."
39 :version "24.1"
40 :group 'electricity
41 :type '(repeat (cons character character)))
43 ;;;###autoload
44 (defcustom electric-pair-text-pairs
45 '((?\" . ?\" ))
46 "Alist of pairs that should always be used in comments and strings.
48 Pairs of delimiters in this list are a fallback in case they have
49 no syntax relevant to `electric-pair-mode' in the syntax table
50 defined in `electric-pair-text-syntax-table'"
51 :version "24.4"
52 :group 'electricity
53 :type '(repeat (cons character character)))
55 (defcustom electric-pair-skip-self #'electric-pair-default-skip-self
56 "If non-nil, skip char instead of inserting a second closing paren.
58 When inserting a closing paren character right before the same character,
59 just skip that character instead, so that hitting ( followed by ) results
60 in \"()\" rather than \"())\".
62 This can be convenient for people who find it easier to hit ) than C-f.
64 Can also be a function of one argument (the closer char just
65 inserted), in which case that function's return value is
66 considered instead."
67 :version "24.1"
68 :group 'electricity
69 :type '(choice
70 (const :tag "Never skip" nil)
71 (const :tag "Help balance" electric-pair-default-skip-self)
72 (const :tag "Always skip" t)
73 function))
75 (defcustom electric-pair-inhibit-predicate
76 #'electric-pair-default-inhibit
77 "Predicate to prevent insertion of a matching pair.
79 The function is called with a single char (the opening char just inserted).
80 If it returns non-nil, then `electric-pair-mode' will not insert a matching
81 closer."
82 :version "24.4"
83 :group 'electricity
84 :type '(choice
85 (const :tag "Conservative" electric-pair-conservative-inhibit)
86 (const :tag "Help balance" electric-pair-default-inhibit)
87 (const :tag "Always pair" ignore)
88 function))
90 (defcustom electric-pair-preserve-balance t
91 "Non-nil if default pairing and skipping should help balance parentheses.
93 The default values of `electric-pair-inhibit-predicate' and
94 `electric-pair-skip-self' check this variable before delegating to other
95 predicates responsible for making decisions on whether to pair/skip some
96 characters based on the actual state of the buffer's parentheses and
97 quotes."
98 :version "24.4"
99 :group 'electricity
100 :type 'boolean)
102 (defcustom electric-pair-delete-adjacent-pairs t
103 "If non-nil, backspacing an open paren also deletes adjacent closer.
105 Can also be a function of no arguments, in which case that function's
106 return value is considered instead."
107 :version "24.4"
108 :group 'electricity
109 :type '(choice
110 (const :tag "Yes" t)
111 (const :tag "No" nil)
112 function))
114 (defcustom electric-pair-open-newline-between-pairs t
115 "If non-nil, a newline between adjacent parentheses opens an extra one.
117 Can also be a function of no arguments, in which case that function's
118 return value is considered instead."
119 :version "24.4"
120 :group 'electricity
121 :type '(choice
122 (const :tag "Yes" t)
123 (const :tag "No" nil)
124 function))
126 (defcustom electric-pair-skip-whitespace t
127 "If non-nil skip whitespace when skipping over closing parens.
129 The specific kind of whitespace skipped is given by the variable
130 `electric-pair-skip-whitespace-chars'.
132 The symbol `chomp' specifies that the skipped-over whitespace
133 should be deleted.
135 Can also be a function of no arguments, in which case that function's
136 return value is considered instead."
137 :version "24.4"
138 :group 'electricity
139 :type '(choice
140 (const :tag "Yes, jump over whitespace" t)
141 (const :tag "Yes, and delete whitespace" chomp)
142 (const :tag "No, no whitespace skipping" nil)
143 function))
145 (defcustom electric-pair-skip-whitespace-chars (list ?\t ?\s ?\n)
146 "Whitespace characters considered by `electric-pair-skip-whitespace'."
147 :version "24.4"
148 :group 'electricity
149 :type '(choice (set (const :tag "Space" ?\s)
150 (const :tag "Tab" ?\t)
151 (const :tag "Newline" ?\n))
152 (list character)))
154 (defun electric-pair--skip-whitespace ()
155 "Skip whitespace forward, not crossing comment or string boundaries."
156 (let ((saved (point))
157 (string-or-comment (nth 8 (syntax-ppss))))
158 (skip-chars-forward (apply #'string electric-pair-skip-whitespace-chars))
159 (unless (eq string-or-comment (nth 8 (syntax-ppss)))
160 (goto-char saved))))
162 (defvar electric-pair-text-syntax-table prog-mode-syntax-table
163 "Syntax table used when pairing inside comments and strings.
165 `electric-pair-mode' considers this syntax table only when point in inside
166 quotes or comments. If lookup fails here, `electric-pair-text-pairs' will
167 be considered.")
169 (defun electric-pair-backward-delete-char (n &optional killflag untabify)
170 "Delete characters backward, and maybe also two adjacent paired delimiters.
172 Remaining behavior is given by `backward-delete-char' or, if UNTABIFY is
173 non-nil, `backward-delete-char-untabify'."
174 (interactive "*p\nP")
175 (let* ((prev (char-before))
176 (next (char-after))
177 (syntax-info (and prev
178 (electric-pair-syntax-info prev)))
179 (syntax (car syntax-info))
180 (pair (cadr syntax-info)))
181 (when (and next pair
182 (if (functionp electric-pair-delete-adjacent-pairs)
183 (funcall electric-pair-delete-adjacent-pairs)
184 electric-pair-delete-adjacent-pairs)
185 (memq syntax '(?\( ?\" ?\$))
186 (eq pair next))
187 (delete-char 1 killflag))
188 (if untabify
189 (backward-delete-char-untabify n killflag)
190 (backward-delete-char n killflag))))
192 (defun electric-pair-backward-delete-char-untabify (n &optional killflag)
193 "Delete characters backward, and maybe also two adjacent paired delimiters.
195 Remaining behavior is given by `backward-delete-char-untabify'."
196 (interactive "*p\nP")
197 (electric-pair-backward-delete-char n killflag t))
199 (defun electric-pair-conservative-inhibit (char)
201 ;; I find it more often preferable not to pair when the
202 ;; same char is next.
203 (eq char (char-after))
204 ;; Don't pair up when we insert the second of "" or of ((.
205 (and (eq char (char-before))
206 (eq char (char-before (1- (point)))))
207 ;; I also find it often preferable not to pair next to a word.
208 (eq (char-syntax (following-char)) ?w)))
210 (defun electric-pair-syntax-info (command-event)
211 "Calculate a list (SYNTAX PAIR UNCONDITIONAL STRING-OR-COMMENT-START).
213 SYNTAX is COMMAND-EVENT's syntax character. PAIR is
214 COMMAND-EVENT's pair. UNCONDITIONAL indicates the variables
215 `electric-pair-pairs' or `electric-pair-text-pairs' were used to
216 lookup syntax. STRING-OR-COMMENT-START indicates that point is
217 inside a comment of string."
218 (let* ((pre-string-or-comment (nth 8 (save-excursion
219 (syntax-ppss (1- (point))))))
220 (post-string-or-comment (nth 8 (syntax-ppss (point))))
221 (string-or-comment (and post-string-or-comment
222 pre-string-or-comment))
223 (table (if string-or-comment
224 electric-pair-text-syntax-table
225 (syntax-table)))
226 (table-syntax-and-pair (with-syntax-table table
227 (list (char-syntax command-event)
228 (or (matching-paren command-event)
229 command-event))))
230 (fallback (if string-or-comment
231 (append electric-pair-text-pairs
232 electric-pair-pairs)
233 electric-pair-pairs))
234 (direct (assq command-event fallback))
235 (reverse (rassq command-event fallback)))
236 (cond
237 ((memq (car table-syntax-and-pair)
238 '(?\" ?\( ?\) ?\$))
239 (append table-syntax-and-pair (list nil string-or-comment)))
240 (direct (if (eq (car direct) (cdr direct))
241 (list ?\" command-event t string-or-comment)
242 (list ?\( (cdr direct) t string-or-comment)))
243 (reverse (list ?\) (car reverse) t string-or-comment)))))
245 (defun electric-pair--insert (char)
246 (let ((last-command-event char)
247 (blink-matching-paren nil)
248 (electric-pair-mode nil))
249 (self-insert-command 1)))
251 (defun electric-pair--syntax-ppss (&optional pos where)
252 "Like `syntax-ppss', but sometimes fallback to `parse-partial-sexp'.
254 WHERE is list defaulting to '(string comment) and indicates
255 when to fallback to `parse-partial-sexp'."
256 (let* ((pos (or pos (point)))
257 (where (or where '(string comment)))
258 (quick-ppss (syntax-ppss))
259 (quick-ppss-at-pos (syntax-ppss pos)))
260 (if (or (and (nth 3 quick-ppss) (memq 'string where))
261 (and (nth 4 quick-ppss) (memq 'comment where)))
262 (with-syntax-table electric-pair-text-syntax-table
263 (parse-partial-sexp (1+ (nth 8 quick-ppss)) pos))
264 ;; HACK! cc-mode apparently has some `syntax-ppss' bugs
265 (if (memq major-mode '(c-mode c++ mode))
266 (parse-partial-sexp (point-min) pos)
267 quick-ppss-at-pos))))
269 ;; Balancing means controlling pairing and skipping of parentheses so
270 ;; that, if possible, the buffer ends up at least as balanced as
271 ;; before, if not more. The algorithm is slightly complex because some
272 ;; situations like "()))" need pairing to occur at the end but not at
273 ;; the beginning. Balancing should also happen independently for
274 ;; different types of parentheses, so that having your {}'s unbalanced
275 ;; doesn't keep `electric-pair-mode' from balancing your ()'s and your
276 ;; []'s.
277 (defun electric-pair--balance-info (direction string-or-comment)
278 "Examine lists forward or backward according to DIRECTION's sign.
280 STRING-OR-COMMENT is info suitable for running `parse-partial-sexp'.
282 Return a cons of two descriptions (MATCHED-P . PAIR) for the
283 innermost and outermost lists that enclose point. The outermost
284 list enclosing point is either the first top-level or first
285 mismatched list found by listing up.
287 If the outermost list is matched, don't rely on its PAIR. If
288 point is not enclosed by any lists, return ((T) . (T))."
289 (let* (innermost
290 outermost
291 (table (if string-or-comment
292 electric-pair-text-syntax-table
293 (syntax-table)))
294 (at-top-level-or-equivalent-fn
295 ;; called when `scan-sexps' ran perfectly, when when it
296 ;; found a parenthesis pointing in the direction of
297 ;; travel. Also when travel started inside a comment and
298 ;; exited it
299 #'(lambda ()
300 (setq outermost (list t))
301 (unless innermost
302 (setq innermost (list t)))))
303 (ended-prematurely-fn
304 ;; called when `scan-sexps' crashed against a parenthesis
305 ;; pointing opposite the direction of travel. After
306 ;; traversing that character, the idea is to travel one sexp
307 ;; in the opposite direction looking for a matching
308 ;; delimiter.
309 #'(lambda ()
310 (let* ((pos (point))
311 (matched
312 (save-excursion
313 (cond ((< direction 0)
314 (condition-case nil
315 (eq (char-after pos)
316 (with-syntax-table table
317 (matching-paren
318 (char-before
319 (scan-sexps (point) 1)))))
320 (scan-error nil)))
322 ;; In this case, no need to use
323 ;; `scan-sexps', we can use some
324 ;; `electric-pair--syntax-ppss' in this
325 ;; case (which uses the quicker
326 ;; `syntax-ppss' in some cases)
327 (let* ((ppss (electric-pair--syntax-ppss
328 (1- (point))))
329 (start (car (last (nth 9 ppss))))
330 (opener (char-after start)))
331 (and start
332 (eq (char-before pos)
333 (or (with-syntax-table table
334 (matching-paren opener))
335 opener))))))))
336 (actual-pair (if (> direction 0)
337 (char-before (point))
338 (char-after (point)))))
339 (unless innermost
340 (setq innermost (cons matched actual-pair)))
341 (unless matched
342 (setq outermost (cons matched actual-pair)))))))
343 (save-excursion
344 (while (not outermost)
345 (condition-case err
346 (with-syntax-table table
347 (scan-sexps (point) (if (> direction 0)
348 (point-max)
349 (- (point-max))))
350 (funcall at-top-level-or-equivalent-fn))
351 (scan-error
352 (cond ((or
353 ;; some error happened and it is not of the "ended
354 ;; prematurely" kind"...
355 (not (string-match "ends prematurely" (nth 1 err)))
356 ;; ... or we were in a comment and just came out of
357 ;; it.
358 (and string-or-comment
359 (not (nth 8 (syntax-ppss)))))
360 (funcall at-top-level-or-equivalent-fn))
362 ;; exit the sexp
363 (goto-char (nth 3 err))
364 (funcall ended-prematurely-fn)))))))
365 (cons innermost outermost)))
367 (defun electric-pair--looking-at-unterminated-string-p (char)
368 "Say if following string starts with CHAR and is unterminated."
369 ;; FIXME: ugly/naive
370 (save-excursion
371 (skip-chars-forward (format "^%c" char))
372 (while (not (zerop (% (save-excursion (skip-syntax-backward "\\")) 2)))
373 (unless (eobp)
374 (forward-char 1)
375 (skip-chars-forward (format "^%c" char))))
376 (and (not (eobp))
377 (condition-case nil
378 (progn (forward-sexp) nil)
379 (scan-error t)))))
381 (defun electric-pair--inside-string-p (char)
382 "Say if point is inside a string started by CHAR.
384 A comments text is parsed with `electric-pair-text-syntax-table'.
385 Also consider strings within comments, but not strings within
386 strings."
387 ;; FIXME: could also consider strings within strings by examining
388 ;; delimiters.
389 (let* ((ppss (electric-pair--syntax-ppss (point) '(comment))))
390 (memq (nth 3 ppss) (list t char))))
392 (defun electric-pair-inhibit-if-helps-balance (char)
393 "Return non-nil if auto-pairing of CHAR would hurt parentheses' balance.
395 Works by first removing the character from the buffer, then doing
396 some list calculations, finally restoring the situation as if nothing
397 happened."
398 (pcase (electric-pair-syntax-info char)
399 (`(,syntax ,pair ,_ ,s-or-c)
400 (unwind-protect
401 (progn
402 (delete-char -1)
403 (cond ((eq ?\( syntax)
404 (let* ((pair-data
405 (electric-pair--balance-info 1 s-or-c))
406 (outermost (cdr pair-data)))
407 (cond ((car outermost)
408 nil)
410 (eq (cdr outermost) pair)))))
411 ((eq syntax ?\")
412 (electric-pair--looking-at-unterminated-string-p char))))
413 (insert-char char)))))
415 (defun electric-pair-skip-if-helps-balance (char)
416 "Return non-nil if skipping CHAR would benefit parentheses' balance.
418 Works by first removing the character from the buffer, then doing
419 some list calculations, finally restoring the situation as if nothing
420 happened."
421 (pcase (electric-pair-syntax-info char)
422 (`(,syntax ,pair ,_ ,s-or-c)
423 (unwind-protect
424 (progn
425 (delete-char -1)
426 (cond ((eq syntax ?\))
427 (let* ((pair-data
428 (electric-pair--balance-info
429 -1 s-or-c))
430 (innermost (car pair-data))
431 (outermost (cdr pair-data)))
432 (and
433 (cond ((car outermost)
434 (car innermost))
435 ((car innermost)
436 (not (eq (cdr outermost) pair)))))))
437 ((eq syntax ?\")
438 (electric-pair--inside-string-p char))))
439 (insert-char char)))))
441 (defun electric-pair-default-skip-self (char)
442 (if electric-pair-preserve-balance
443 (electric-pair-skip-if-helps-balance char)
446 (defun electric-pair-default-inhibit (char)
447 (if electric-pair-preserve-balance
448 (electric-pair-inhibit-if-helps-balance char)
449 (electric-pair-conservative-inhibit char)))
451 (defun electric-pair-post-self-insert-function ()
452 (let* ((pos (and electric-pair-mode (electric--after-char-pos)))
453 (skip-whitespace-info))
454 (pcase (electric-pair-syntax-info last-command-event)
455 (`(,syntax ,pair ,unconditional ,_)
456 (cond
457 ((null pos) nil)
458 ;; Wrap a pair around the active region.
460 ((and (memq syntax '(?\( ?\) ?\" ?\$)) (use-region-p))
461 ;; FIXME: To do this right, we'd need a post-self-insert-function
462 ;; so we could add-function around it and insert the closer after
463 ;; all the rest of the hook has run.
464 (if (or (eq syntax ?\")
465 (and (eq syntax ?\))
466 (>= (point) (mark)))
467 (and (not (eq syntax ?\)))
468 (>= (mark) (point))))
469 (save-excursion
470 (goto-char (mark))
471 (electric-pair--insert pair))
472 (delete-region pos (1- pos))
473 (electric-pair--insert pair)
474 (goto-char (mark))
475 (electric-pair--insert last-command-event)))
476 ;; Backslash-escaped: no pairing, no skipping.
477 ((save-excursion
478 (goto-char (1- pos))
479 (not (zerop (% (skip-syntax-backward "\\") 2))))
480 nil)
481 ;; Skip self.
482 ((and (memq syntax '(?\) ?\" ?\$))
483 (and (or unconditional
484 (if (functionp electric-pair-skip-self)
485 (funcall electric-pair-skip-self last-command-event)
486 electric-pair-skip-self))
487 (save-excursion
488 (when (setq skip-whitespace-info
489 (if (functionp electric-pair-skip-whitespace)
490 (funcall electric-pair-skip-whitespace)
491 electric-pair-skip-whitespace))
492 (electric-pair--skip-whitespace))
493 (eq (char-after) last-command-event))))
494 ;; This is too late: rather than insert&delete we'd want to only
495 ;; skip (or insert in overwrite mode). The difference is in what
496 ;; goes in the undo-log and in the intermediate state which might
497 ;; be visible to other post-self-insert-hook. We'll just have to
498 ;; live with it for now.
499 (when skip-whitespace-info
500 (electric-pair--skip-whitespace))
501 (delete-region (1- pos) (if (eq skip-whitespace-info 'chomp)
502 (point)
503 pos))
504 (forward-char))
505 ;; Insert matching pair.
506 ((and (memq syntax `(?\( ?\" ?\$))
507 (not overwrite-mode)
508 (or unconditional
509 (not (funcall electric-pair-inhibit-predicate
510 last-command-event))))
511 (save-excursion (electric-pair--insert pair)))))
513 (when (and (if (functionp electric-pair-open-newline-between-pairs)
514 (funcall electric-pair-open-newline-between-pairs)
515 electric-pair-open-newline-between-pairs)
516 (eq last-command-event ?\n)
517 (< (1+ (point-min)) (point) (point-max))
518 (eq (save-excursion
519 (skip-chars-backward "\t\s")
520 (char-before (1- (point))))
521 (matching-paren (char-after))))
522 (save-excursion (newline 1 t)))))))
524 (put 'electric-pair-post-self-insert-function 'priority 20)
526 (defun electric-pair-will-use-region ()
527 (and (use-region-p)
528 (memq (car (electric-pair-syntax-info last-command-event))
529 '(?\( ?\) ?\" ?\$))))
531 (defvar electric-pair-mode-map
532 (let ((map (make-sparse-keymap)))
533 (define-key map [remap backward-delete-char-untabify]
534 'electric-pair-backward-delete-char-untabify)
535 (define-key map [remap backward-delete-char]
536 'electric-pair-backward-delete-char)
537 (define-key map [remap delete-backward-char]
538 'electric-pair-backward-delete-char)
539 map)
540 "Keymap used by `electric-pair-mode'.")
542 ;;;###autoload
543 (define-minor-mode electric-pair-mode
544 "Toggle automatic parens pairing (Electric Pair mode).
545 With a prefix argument ARG, enable Electric Pair mode if ARG is
546 positive, and disable it otherwise. If called from Lisp, enable
547 the mode if ARG is omitted or nil.
549 Electric Pair mode is a global minor mode. When enabled, typing
550 an open parenthesis automatically inserts the corresponding
551 closing parenthesis. \(Likewise for brackets, etc.)."
552 :global t :group 'electricity
553 (if electric-pair-mode
554 (progn
555 (add-hook 'post-self-insert-hook
556 #'electric-pair-post-self-insert-function)
557 (electric--sort-post-self-insertion-hook)
558 (add-hook 'self-insert-uses-region-functions
559 #'electric-pair-will-use-region))
560 (remove-hook 'post-self-insert-hook
561 #'electric-pair-post-self-insert-function)
562 (remove-hook 'self-insert-uses-region-functions
563 #'electric-pair-will-use-region)))
565 (provide 'elec-pair)
567 ;;; elec-pair.el ends here