highlightjs/highlight.js

(ruby) Syntax highlight fails with `%r/` Ruby expression

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#4,281 opened on Jun 10, 2025

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Description

Describe the issue Ruby syntax highlight fails with %r Ruby expression. See screenshot:

Which language seems to have the issue?

Ruby

Are you using highlight or highlightAuto?

  • highlight

...

Sample Code to Reproduce

  # Validations
  validates :creator, presence: true, on: :create
  validates :description, length: { maximum: 2000 }, allow_blank: true
  validates :ci_config_path,
    format: { without: %r{(\.{2}|\A/)},
              message: N_('cannot include leading slash or directory traversal.') },
    length: { maximum: 255 },
    allow_blank: true
  validates :name,
    presence: true,
    length: { maximum: 255 }
  validates :path,
    presence: true,
    project_path: true,
    length: { maximum: 255 }

Expected behavior Syntax highlighting should work as expected after %r/ Ruby expression

Additional context

Full example file can be found here: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/project.rb

Contributor guide

Tech stack
javascriptruby
Domain
frontendtooling
Issue type
bug
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.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Knowledge of Ruby regular expressionsFamiliarity with highlight.js language definitions
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
85
Research direction
Examine the Ruby language definition file in highlight.js (likely /src/languages/ruby.js). Look for the regex pattern that matches `%r/` expressions and adjust it to correctly highlight the content between the delimiters. The issue provides a sample Ruby code snippet that fails, so you can use that to test changes. The expected behavior is that syntax highlighting works correctly after `%r/`.
(ruby) Syntax highlight fails with `%r/` Ruby expression · highlightjs/highlight.js#4281 | Good First Issue