hound-search/hound

Lookaround assertions in regular expressions?

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#305 opened on Feb 19, 2019

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enhancementhelp wanted

Description

If I write a regular expression with a (positive or negative) lookahead (or lookbehind) assertion I get an error saying it's incorrect Perl syntax.

For example to look for the text "function" that's not followed by an underscore, I might use this: function(?!_)

However that returns the error: ERROR:error parsing regexp: invalid or unsupported Perl syntax: (?!

However they do work in Perl!

Any ideas?

PS: In this toy example I could use a negated character class function[^_] for searching, but I'm interested in the general case rather than a solution to a specific pattern.

Contributor guide

Tech stack
go
Domain
backendsearch
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Go programmingregular expressionsregex engines
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Look into the regex parsing code in the hound codebase, likely using Go's regexp package. Determine if there is an alternative regex library that supports lookaheads (e.g., RE2) and evaluate the feasibility of integrating it. Also check if there are existing issues or discussions about this feature.