hound-search/hound

Lookaround assertions in regular expressions?

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#305 opened on Feb 19, 2019

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enhancementhelp wanted

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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

Research direction
Investigate adding lookahead/lookbehind support to Hound's regex engine. Consider alternatives like switching to RE2 or implementing custom regex post processing.
Tech stack
gojavascript
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Goregex
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65