Unexpected regex match

[alexdima]

In the sample/bug_fix.c file, insert the following:

  exec(ONIG_ENCODING_UTF8, ONIG_OPTION_FIND_LONGEST,
       "(?x)\n  (?<!\\+\\+|--)(?<=[({\\[,?=>:*]|&&|\\|\\||\\?|\\*\\/|^await|[^\\._$[:alnum:]]await|^return|[^\\._$[:alnum:]]return|^default|[^\\._$[:alnum:]]default|^yield|[^\\._$[:alnum:]]yield|^)\\s*\n  (?!<\\s*[_$[:alpha:]][_$[:alnum:]]*((\\s+extends\\s+[^=>])|,)) # look ahead is not type parameter of arrow\n  (?=(<)\\s*(?:([_$[:alpha:]][-_$[:alnum:].]*)(?<!\\.|-)(:))?((?:[a-z][a-z0-9]*|([_$[:alpha:]][-_$[:alnum:].]*))(?<!\\.|-))(?=((<\\s*)|(\\s+))(?!\\?)|\\/?>))", "    while (i < len && f(array[i]))");

I would expect to see in the output:

search fail (UTF-8)

But instead there is printed:

match at 12  (UTF-8)
0: (12-13)
1: (-1--1)
2: (-1--1)
3: (13-14)
4: (-1--1)
5: (-1--1)
6: (15-18)
7: (-1--1)
8: (18-19)
9: (-1--1)
10: (18-19)

I have done git bisect and it led towards 32e688b:

32e688b0c71bd3912867c5107a5efdbcdde3ff2c is the first bad commit
commit 32e688b0c71bd3912867c5107a5efdbcdde3ff2c
Author: K.Kosako <kosako@sofnec.co.jp>
Date:   Tue Jan 21 08:37:19 2020 +0900

    optimize for min len == 0 and min len is sure case

I am sorry for the very complex regular expression and for not spending more time to simplify it, but I believe it has something to do with the look behind starting with (?<=[({\\[ ... . It is almost as if it is not checked. I have hit this regular expression in VS Code's JavaScript TM grammar, while validating/updating VS Code's oniguruma version with a fresh WASM implementation here.

Thank you for your great work, and special thanks for the new RegSet API, which might save a lot of time in parsing TM grammars.

[kkos]

Thank you for your research.
Fixed.
This is a bug that if the look-behind contains a branch with a character length of 0 and an anchor is included in the branch, the whole look-behind is ignored.

It may be quite serious, so an urgent release may be needed.
But there may be some other problems, so wait a while.