* Font-lock should ignore missing submatches
@ 2008-02-03 20:30 Jorgen Schaefer
2008-02-04 5:12 ` Chong Yidong
0 siblings, 1 reply; 2+ messages in thread
From: Jorgen Schaefer @ 2008-02-03 20:30 UTC (permalink / raw)
To: bug-gnu-emacs
Hello!
When using font-lock-mode to highlight complex expressions, the
font locking engine crashes when one of the subexpressions
specified was not matched.
Consider:
(set (make-local-variable 'font-lock-keywords)
'(("\\(?:\\(foo\\) *\\)?\\(bar\\)"
(1 font-lock-comment-face)
(2 font-lock-string-face))))
I.e. "possibly match the foo that is followed by whitespace, then
definitively match a bar."
This will (correctly) highlight these expressions:
foobar
foo bar
etc.
But font-lock will error out if the first subexpression does not
match anything, even though the regular expression matches:
oobar
oo bar
bar
etc.
The code will give an appropriate error:
Error during redisplay: (error No match 1 in highlight (1
font-lock-comment-face))
Is there any chance to make font-lock just ignore unmatched
subexpressions?
Tested in:
- GNU Emacs 22.1.1
- GNU Emacs from CVS, approx. two weeks old
Sorry, no current CVS version here :-(
Regards,
-- Jorgen
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Font-lock should ignore missing submatches
2008-02-03 20:30 Font-lock should ignore missing submatches Jorgen Schaefer
@ 2008-02-04 5:12 ` Chong Yidong
0 siblings, 0 replies; 2+ messages in thread
From: Chong Yidong @ 2008-02-04 5:12 UTC (permalink / raw)
To: bug-gnu-emacs
Jorgen Schaefer <forcer@forcix.cx> writes:
> When using font-lock-mode to highlight complex expressions, the
> font locking engine crashes when one of the subexpressions
> specified was not matched.
The engine doesn't "crash"; it signals an error, and Emacs continues
to function. This is the intended behavior.
> Is there any chance to make font-lock just ignore unmatched
> subexpressions?
Yes. See the LAXMATCH option in the node Customizing Keywords in the
Emacs Lisp Reference Manual.
^ permalink raw reply [flat|nested] 2+ messages in thread
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