## Description
This isn't tied to an open issue — I found it by extrapolating from the
bug class fixed in #15415 ("fix: anchor contact phone number
validation"), which fixed a `Contact#phone_number` format validation
that was missing a leading `\A` anchor. That made me audit every
hand-written regex-based validation in the codebase for the same class
of anchoring mistake (`format: { with: ... }` validators, plus
`match?`/`=~` calls used for validation-style checks, across `app/`,
`enterprise/`, and `lib/`).
Everything else was already correctly anchored. One real instance of the
*sibling* mistake remains:
`RegexHelper::UNICODE_CHARACTER_NUMBER_HYPHEN_UNDERSCORE` (used only by
`Label#title`'s format validation) is
`/\A[\p{L}\p{N}]+[\p{L}\p{N}_-]+\Z/` — note `\Z` (capital), not `\z`.
Unlike `\z`, `\Z` also matches just before a single trailing `"\n"` at
the end of the string. The surrounding comment documents the intended
character set (unicode letters/numbers/underscore/hyphen, not starting
with `_`/`-`) and says nothing about tolerating a trailing newline, so
this reads as an unintentional choice of anchor rather than a deliberate
one.
Concretely: `Label.new(title: "hello_world\n").valid?` returns `true` on
current `develop` and persists a title with a literal trailing newline,
because `\Z` lets the `\n` slip through. `Label` only lowercases the
title before validating (no `strip`), so nothing else catches this.
This is a narrower/lower-severity variant of the #15415 bug (it only
ever admits one specific trailing character, not an arbitrary
prefix/suffix), but it's the same underlying mistake, independently
verified against current source, not just pattern-matched from the diff.
## What changed
- `lib/regex_helper.rb`: `UNICODE_CHARACTER_NUMBER_HYPHEN_UNDERSCORE`
now ends in `\z` instead of `\Z`, with a comment explaining why.
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
Ran against a real local Rails env (Ruby 3.4.4, PostgreSQL 16, Redis):
`bundle exec rspec spec/models/label_spec.rb`
Added a regression test asserting `Label.new(title: "hello_world\n")` is
invalid. Confirmed it fails against the pre-fix `\Z` regex and passes
after switching to `\z`. All existing `label_spec.rb` examples
(including the existing "foreign characters", "special characters", and
"uppercase" title-validation cases) continue to pass unchanged.
## Checklist
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective
- [x] New and existing unit tests pass locally with my changes
🤖 This fix was authored by an AI coding agent (Claude) working on behalf
of Mithtech, an ERPNext/Frappe/Medusa.js implementation studio, as part
of a deliberate effort to build a track record of verified upstream
open-source contributions. Flagging this transparently per common
courtesy — happy to answer any questions about the change, including how
it was found (auditing for the same regex-anchor mistake class as
#15415).
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
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