Commit afdc20d7 authored by Mattias Engdegård's avatar Mattias Engdegård

Allow zero-argument rx `or' and `seq' forms

Make the rx `or' and `seq' forms accept zero arguments to produce a
never-matching regexp and an empty string, respectively.

* lisp/emacs-lisp/rx.el: Require cl-extra.
(rx-constituents, rx-or): Permit zero args.
(rx): Amend doc string for `or' and `seq'.
* test/lisp/emacs-lisp/rx-tests.el (rx-or, rx-seq): Test the change.
* etc/NEWS (Changes in Specialized Modes and Packages): Mention the change.
parent c2cda3ff
Pipeline #1760 failed with stage
in 52 minutes and 5 seconds
......@@ -1321,6 +1321,12 @@ when given in a string. Previously, '(any "\x80-\xff")' would match
characters U+0080...U+00FF. Now the expression matches raw bytes in
the 128...255 range, as expected.
*** The rx 'or' and 'seq' forms no longer require any arguments.
(or) produces a regexp that never matches anything, while (seq)
matches the empty string, each being an identity for the operation.
This also works for their aliases: '|' for 'or'; ':', 'and' and
'sequence' for 'seq'.
** Frames
+++
......
......@@ -106,15 +106,16 @@
;;; Code:
(require 'cl-lib)
(require 'cl-extra)
;; FIXME: support macros.
(defvar rx-constituents ;Not `const' because some modes extend it.
'((and . (rx-and 1 nil))
'((and . (rx-and 0 nil))
(seq . and) ; SRE
(: . and) ; SRE
(sequence . and) ; sregex
(or . (rx-or 1 nil))
(or . (rx-or 0 nil))
(| . or) ; SRE
(not-newline . ".")
(nonl . not-newline) ; SRE
......@@ -390,9 +391,11 @@ FORM is of the form `(and FORM1 ...)'."
"Parse and produce code from FORM, which is `(or FORM1 ...)'."
(rx-check form)
(rx-group-if
(if (memq nil (mapcar 'stringp (cdr form)))
(mapconcat (lambda (x) (rx-form x '|)) (cdr form) "\\|")
(cond
((null (cdr form)) regexp-unmatchable)
((cl-every #'stringp (cdr form))
(regexp-opt (cdr form) nil t))
(t (mapconcat (lambda (x) (rx-form x '|)) (cdr form) "\\|")))
(and (memq rx-parent '(: * t)) rx-parent)))
......@@ -1121,6 +1124,7 @@ CHAR
`(seq SEXP1 SEXP2 ...)'
`(sequence SEXP1 SEXP2 ...)'
matches what SEXP1 matches, followed by what SEXP2 matches, etc.
Without arguments, matches the empty string.
`(submatch SEXP1 SEXP2 ...)'
`(group SEXP1 SEXP2 ...)'
......@@ -1136,7 +1140,7 @@ CHAR
`(| SEXP1 SEXP2 ...)'
matches anything that matches SEXP1 or SEXP2, etc. If all
args are strings, use `regexp-opt' to optimize the resulting
regular expression.
regular expression. Without arguments, never matches anything.
`(minimal-match SEXP)'
produce a non-greedy regexp for SEXP. Normally, regexps matching
......
......@@ -107,7 +107,13 @@
"ab"))
(should (equal (and (string-match (rx (or "a" "ab" "abc")) s)
(match-string 0 s))
"a"))))
"a")))
;; Test zero-argument `or'.
(should (equal (rx (or)) regexp-unmatchable)))
(ert-deftest rx-seq ()
;; Test zero-argument `seq'.
(should (equal (rx (seq)) "")))
(provide 'rx-tests)
;; rx-tests.el ends here.
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