Hi Ivan,
The code handles group name was added later. So "historically" those cases
trigger "unknow look-behind group" when the first character after "<" is not
"=" or "?". With the addition of the group name support, it's actually
hard to
say which one is more accurate, incorrect group name or incorrect "looks
behind". Sure with a tailing ">" it might be more desired to lean to group
name.
It's definitely a bug not to check whether or not the first char is
alpha for \\k<.
I'm fine with the proposed change.
Thanks,
Sherman
On 2/8/18, 8:32 PM, Ivan Gerasimov wrote:
Hello!
Capturing group name can be used in a regular expression in two
contexts: When introducing a group (?<name>...) or when referring it
\k<name>.
If the name is invalid (i.e. does not start with a Latin letter, or
contains wrong chars) then we may see different error messages, some
of which look confusing.
Here are examples of the messages produced by the current JDK:
Unknown look-behind group near index 3
(?<>)
^
named capturing group is missing trailing '>' near index 4
\\k<>
^
Unknown look-behind group near index 4
(?<.>)
^
(named capturing group <.> does not exit near index 4
\\k<.>
^
named capturing group is missing trailing '>' near index 4
(?<a.>)
^
named capturing group is missing trailing '>' near index 4
\\k<a.>
^
In particular, this diversity is caused by that the internal
Pattern.groupname() function lacks a check for the very first
character of the name.
So that when \k<name> is parsed, the first char is always accepted, no
matter what it was.
Some cleanup was also done along the way.
Would you please help review the fix?
BUGURL: https://bugs.openjdk.java.net/browse/JDK-8197462
WEBREV: http://cr.openjdk.java.net/~igerasim/8197462/00/webrev/
Thanks in advance!
