Support positiv/negative lookahead/lookbehing regex syntax

[bastilimbach]

It would be great if the regex engine would support lookahead & lookbehinds to support searches like /init(?=\W)/ (Search the word init which ends with any non-word character).

This is probably not supported due to the reason that the code search is build in rust and the rust regex crate doesn't support it:

This crate provides a library for parsing, compiling, and executing regular expressions. Its syntax is similar to Perl-style regular expressions, but lacks a few features like look around and backreferences. In exchange, all searches execute in linear time with respect to the size of the regular expression and search text.

https://docs.rs/regex/latest/regex/ 😢

[h-vetinari]

Another closely related feature that unfortunately does not seep supported by the regex crate: possessive qualifiers (which go hand in hand with lookaheads to me, because if there's something optional before the lookahead, you definitely don't want the engine to backtrack)

[look]

Thanks for the feedback. As noted by the documentation you quoted, these regular expression features cause non-linear runtimes. This is why we do not support them and do not plan to support them.