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Allow empty argument to `regexp-opt-charset'

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* test/lisp/emacs-lisp/regexp-opt-tests.el (regexp-opt-charset):
Handle nil argument, and use regexp-quote for singletons.
* lisp/emacs-lisp/regexp-opt.el (regexp-opt-charset): Expand tests.
This commit is contained in:
Mattias Engdegård 2019-06-29 11:10:36 +02:00
parent 1dfb2f3615
commit f1d414b98f
2 changed files with 36 additions and 13 deletions
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20
lisp/emacs-lisp/regexp-opt.el
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@ -279,7 +279,9 @@ Merges keywords to avoid backtracking in Emacs's regexp matcher."
(defun regexp-opt-charset (chars)
"Return a regexp to match a character in CHARS.
CHARS should be a list of characters."
CHARS should be a list of characters.
If CHARS is the empty list, the return value is a regexp that
never matches anything."
;; The basic idea is to find character ranges. Also we take care in the
;; position of character set meta characters in the character set regexp.
;;
@ -326,13 +328,15 @@ CHARS should be a list of characters."
(while (>= end start)
(setq charset (format "%s%c" charset start))
(setq start (1+ start)))))
;;
;; Make sure a caret is not first and a dash is first or last.
(if (and (string-equal charset "") (string-equal bracket ""))
(if (string-equal dash "")
"\\^" ; [^] is not a valid regexp
(concat "[" dash caret "]"))
(concat "[" bracket charset caret dash "]"))))
;; Make sure that ] is first, ^ is not first, - is first or last.
(let ((all (concat bracket charset caret dash)))
(pcase (length all)
(0 regexp-unmatchable)
(1 (regexp-quote all))
(_ (if (string-equal all "^-")
"[-^]"
(concat "[" all "]")))))))
(defun regexp-opt--contains-prefix (strings)