Hey,
We don't support lookbehind at the moment. We're using https://docs.rs/regex/latest/regex/ under the hood, and it's docs explicitly state:

The regex syntax supported by this crate is similar to other regex engines, but it lacks several features that are not known how to implement efficiently. This includes, but is not limited to, look-around and backreferences. In exchange, all regex searches in this crate have worst case O(m * n) time complexity, where m is proportional to the size of the regex and n is proportional to the size of the string being searched.

I know you're asking for some feature in general (and not for solving a specific use case), but we do support running searches in a selection now. This should allow you to select the last 2 lines in a file and run your query on just these lines.

I don't understand why you are closing this as not planned. There are multiple ways to do better here than just close the issue:

• Use a more capable rust crate for doing regex with lookaheads/lookbehinds. They exist, e.g. https://crates.io/crates/fancy-regex .
• Update the UI so that if a search regex is valid regex, but it's using regex features that Zed doesn't support yet, instead of just making the input an invalid red state, show a validation message explaining what is wrong so the user can stop attempting to debug their regex syntax which is actually perfectly valid.

As an anecdotal sample, In the last couple of weeks, both me and my immediate colleague have been using regex searches with lookbehind/lookahead group constructs to do find and replace refactoring in projects with hundreds of modules. It's not an edge case thing; today I had to fire up VS Code and use its regex find and replace because Zed doesn't have the capability.

I, too, would like to see "look ahead" and "look behind" support in the search.

This issue would be a UX defect/bug/issue. However, there is also a feature request here. I hope we can capture both intents.

The lack of information about my Regex being "wrong" was driving me nuts. I thought I was doing something wrong when trying to create a lookbehind regex, because Zed was giving me a red box, indicating that the regex is wrong, but its not actually wrong, its not supported. It should have this information in the docs or an actual UI message telling that this is not supported (maybe another color, such as orange/yellow).

please, we also want to fully switch to zed, but hickups like (notebook not supported, and regex don't work even as sublime) these are holding that to happen, now I am on a verge to uninstall it, as I am just carrying it's installation in my PC without using it(waiting for it to support) things which are really necessary.

and it's not really me, every zed user have same issues

Please release a version where we can switch ASAP

This is definitely a basic function needed.

fancy-regex (the crate which supports look-arounds) and regex (the crate Zed currently uses) both depend on the same regex-automata engine and regex-syntax parser, so, it's possible to have both without adding "bloat".

A possible solution for user-given patterns is: always use regex, but fallback to fancy-regex if the pattern compilation fails.

(I'm assuming that regex can be faster even for a pattern that compiles in both crates)

Keeping regex usage in the rest of the editor should be a sane decision tho.

It would be really nice to have this feature. It's very powerful for mass search / replace. A bit "niche" in terms of addressable user base, but definitely an important power-feature.

Came here to find this... Do I care if an algorithm is "inefficient" for a computer when the alternate is it being very inefficient for me to manually do stuff? Not one bit. Please reconsider.