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Summary

Titles with unusual punctuation could produce ugly or unsafe slugs because Article.toSlug only replaced a hard-coded set of characters (& ? , ., some fullwidth forms, curly quotes, whitespace). This PR makes slug handling lenient to any punctuation without weakening the tests — per the repo's TDD convention, all five existing ArticleTest slug expectations are kept unchanged and still pass.

// before: enumerated punctuation only
title.toLowerCase().replaceAll("[\\&|[\\uFE30-\\uFFA0]|\\’|\\”|\\s\\?\\,\\.]+", "-");
// after: keep unicode letters/digits, collapse everything else, trim edge dashes
title.toLowerCase().replaceAll("[^\\p{L}\\p{N}]+", "-").replaceAll("^-+|-+$", "");

\p{L}\p{N} preserves non-Latin titles (e.g. 中文：标题 → 中文-标题), so the existing i18n test still passes while Hello, World! → hello-world, 100% #goals → 100-goals, etc.

Note: overlaps with open PR #214 (DJ-84), which solves the same problem for ASCII punctuation only.

Verified locally: ./gradlew clean test spotlessCheck green.

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/ff95e7360720497e81447c11af8e545e

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Tested this end-to-end against a local backend (bootRun, Java 11) + Next.js frontend: created punctuation-heavy articles through the editor UI and loaded every detail page at its generated slug.

Results

• ✅ TDD/BDD basics → /article/tdd-bdd-basics (old regex kept the /, which broke the URL)
• ✅ 100% coverage #goals → /article/100-coverage-goals
• ✅ !!edge!! (case) → /article/edge-case (leading/trailing punctuation trimmed, dashes collapsed)
• ✅ 中文：标题 → /article/中文-标题 (unicode letters kept, fullwidth colon → dash)
• ✅ Title update !!edge!! (case) → Hello, World! regenerates slug hello-world, page loads

More evidence (unicode, %/# stripping, edge case)

⚠️ Known edge case (pre-existing question, not a regression): a punctuation-only title like !!! produces an empty slug. The backend accepts it, but the article is unreachable — the feed links to /article, which errors in the Next.js router:

Empty-slug router error

🎥 Full test recording available in the Devin session.

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Devin Review found 2 potential issues.

[devin-ai-integration]

🟡 Punctuation-only titles create empty slugs

A punctuation-only title makes toSlug return an empty string. The article gets an unusable route, and another such title fails persistence.

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Titles only need to be nonblank, so strings such as "!!!" pass creation validation. The replacement first produces "-", then edge trimming removes it entirely. The empty slug is saved into the unique articles.slug column and is also used as the article's URL identifier. A later punctuation-only title passes the duplicate-title validator only if no empty slug exists, then otherwise is rejected as a duplicate or fails the unique constraint depending on the path.

Example: Creating an article titled "!!!" stores slug = ""; clients cannot address it through the normal /articles/{slug} route. Creating "???" generates the same empty slug.

Recommended fix: Reject titles whose normalized slug is empty, or generate a stable nonempty fallback before constructing and persisting the article. Apply the same rule in DuplicatedArticleValidator so validation and persistence agree.

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🟡 Combining marks corrupt Unicode slugs

A title containing combining marks makes toSlug replace those marks with hyphens. Accented and Indic words become fragmented, producing incorrect identifiers and collisions.

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Unicode combining marks use the \p{M} category, not \p{L} or \p{N}. They include decomposed accents and essential vowel signs in scripts such as Devanagari. The new negated class therefore replaces these marks with hyphens even though they are part of the surrounding word. Different marked forms can consequently normalize to the same slug, which the database requires to be unique.

Example: The decomposed title "e\u0301clair" becomes "e-clair" instead of preserving éclair. "हिन्दी भाषा" becomes "ह-न-द-भ-ष", discarding its vowel signs.

Recommended fix: Normalize the title consistently and preserve combining marks, for example by including \p{M} in the allowed categories. Add tests for decomposed accents and a script whose letters require combining marks.

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