docs-translations

name	docs-translations
description	Explains how localisation works for the Vapor docs site (docs.vapor.codes) and how to replicate a docs change across every language, optionally using AI to do the translations. Use when adding a new page or section, adding or editing a part of an existing page, or adding a completely new language — and you want the change reflected in all supported languages rather than only English.

Vapor Docs Translations

The Vapor docs are generated by Kiln (a Swift site generator) and served at docs.vapor.codes. Every page can exist in multiple languages. This skill explains the moving parts and gives step-by-step recipes — including how to safely use AI for the actual translation — for the three common changes: adding a page/section, editing part of a page, and adding a new language.

How localisation works (the mental model)

There are three separate layers, and a full change usually touches all three:

1. Content — the Markdown under docs/<version>/… (current version is 4.0).

   • English/default: install/macos.md
   • A translation: install/macos.<lang>.md, e.g. install/macos.ja.md
   • <lang> is the language's code (de, es, fr, it, ja, ko, nl, pl, zh, ar). It matches the LanguageCode in Languages.swift, not necessarily the OG-image name (Chinese files are .zh.md but its social card is zh-Hans-2x.png).
   • Fallback is automatic: if foo.<lang>.md doesn't exist, Kiln serves the English foo.md for that language. So partial translations are fine and nothing 404s.

2. Navigation titles — the sidebar tree lives in Sources/VaporDocs/Version4.swift as Page("Title", "path.md") and Section("Title") { … }, always with English titles. Each language translates those titles in Sources/VaporDocs/Languages.swift via navTranslations, keyed by the exact English title. A key that's missing falls back to the English title.

3. UI chrome — search box, prev/next, footer, language/theme pickers, error pages. Translated per language in Languages.swift through customStrings (docs-specific navbar/footer strings, #localise("key") in templates) and localisation: (Kiln's built-in strings). Anything unset falls back to English.

Plus two things outside the generator:

• OG/social card — a per-language 1200×630 (ideally 2×, 2400×1260) PNG at docs/4.0/assets/og/<code>-2x.png, referenced by image: on the Language.
• Language-suggestion banner — the "this site is available in …" banner is driven by the LOCALES map in the shared design repo vapor/design (src/js/languageSuggestion.js). A new language works without it; the banner just won't proactively suggest it.

Supported languages (as of writing)

German de, Spanish es, French fr, Italian it, Japanese ja, Korean ko, Dutch nl, Polish pl, Chinese zh, Arabic ar (RTL). English en is the default/fallback. Always re-derive the current list from the languages array in Sources/VaporDocs/Languages.swift rather than trusting this line.

Build & preview

Requires a Swift 6.2+ toolchain (no Python needed to build):

swift run VaporDocs                        # writes the site to ./site
python3 -m http.server --directory site    # preview at http://localhost:8000

Or docker compose up (serves on port 8000). CI builds the site on every PR with swift run VaporDocs, so a change that doesn't compile (e.g. a broken Languages.swift) will fail the check.

Using AI to do the translations (rules that always apply)

When you translate a Markdown file with AI, translate the prose and leave the structure and code byte-for-byte intact. Concretely:

• DO translate: paragraph text; headings; list items; table cell text; link text; image alt text; blockquote text; the title: and description: fields in the YAML frontmatter; and the custom title of an admonition (!!! note "My title" → translate My title).
• DO NOT translate / must stay identical:
  • Contents of fenced code blocks (```) and inline `code` — including comments unless they're plainly explanatory prose the reader needs.
  • The admonition/type keyword itself: !!! note, !!! warning, !!! tip, !!! seealso stay in English (Kiln maps the keyword; only the optional quoted title is translated).
  • URLs, file paths, API/type/method names, Swift keywords, package names.
  • Markdown structure: heading levels (# count), list markers, table pipes, the frontmatter --- fences and its keys.
  • HTML tags/attributes and their class/id values (e.g. class="kiln-center").
  • Anchor slugs — if a link points to #some-heading, keep the original English anchor unless you also verify the anchor generated for the translated heading.
• Match an existing translation's voice. Before translating for a language, open an existing *.<lang>.md file and mirror its terminology and formality. Reuse the term choices already in that language's navTranslations (e.g. don't invent a new word for "Routing" if the nav already picks one).
• RTL languages (Arabic): translate content normally — Kiln handles direction via isRTL on the .arabic code. Keep code blocks and inline code LTR (they are by default). Arabic in this repo is flagged as a first pass pending native-speaker review; mark AI output the same way.
• Never fabricate. If unsure of a term, leave the English word and flag it in the PR rather than guessing.

A machine translation should be labelled as such in the PR and, ideally, get a native-speaker review before merge. AI gets you a complete, reviewable draft — it is not a substitute for the @vapor/translators review.

---

Recipe A — Add a new page or a new section

Say you added docs/4.0/basics/websockets-guide.md (English).

1. Register it in the nav (Sources/VaporDocs/Version4.swift): add a Page("WebSockets Guide", "basics/websockets-guide.md") in the right Section, or add a whole new Section("New Area") { Page(…) }. Use the English title.
2. Add nav title translations (Sources/VaporDocs/Languages.swift): for every language, add the new English title(s) to its navTranslations map, keyed by the exact English string:

   "WebSockets Guide": "WebSocket-Leitfaden",   // in the German block
   

   Any language you skip will show the English title in its sidebar (acceptable, but the goal is full coverage).
3. Translate the page for each language into basics/websockets-guide.<lang>.md, following the AI rules above. Copy the English file, then translate in place so structure is preserved. Files you omit fall back to English automatically.
4. Build & preview with swift run VaporDocs; switch languages and confirm the page appears, the sidebar title is translated, and code blocks are intact.
5. Track the work — a docs-changing PR normally spawns a translation-needed issue for @vapor/translators. If you already included AI drafts for all languages, note that in the PR; tag translation-only follow-up PRs with the translation-update label so they don't spawn a new issue.

Recipe B — Add or change part of an existing page

Say you added a section to docs/4.0/basics/routing.md (English).

1. Apply the same edit to each translation basics/routing.<lang>.md that exists. For each one, translate only the new/changed portion and splice it into the same structural location, keeping the surrounding translated text as-is.
2. Watch for drift: if a translated file is now shorter/older than English in other places, don't silently rewrite the whole file — scope your change to what actually changed in English, unless you're deliberately doing a full refresh.
3. New headings? If your edit adds a heading and something links to it via an anchor, verify anchors in each language (translated headings produce different slugs). Prefer stable link targets.
4. If a translation for that page doesn't exist yet, you don't have to create it just for this change — English fallback covers it. Creating it is a bonus (that's Recipe A step 3 for a single language).
5. Build, preview each affected language, and note AI-translated files in the PR.

Recipe C — Add a completely new language

Example: adding Portuguese (pt).

1. Add a Language entry to the languages array in Sources/VaporDocs/Languages.swift. Copy an existing complete block (German is a good, fully-populated template) and translate every value:

   Language(
       .portuguese,                 // built-in LanguageCode, OR .custom(code: "xx", name: "…")
       siteName: "Documentação do Vapor",
       description: "Documentação do Vapor (framework web para Swift).",
       navTranslations: [
           // every English nav title from Version4.swift → Portuguese
           "Welcome": "Bem-vindo",
           "Install": "Instalação",
           // …
       ],
       customStrings: [
           // copy the keys from the English block at the top of the file;
           // any you leave out fall back to English
           "tagline": "…",
           "skipToContent": "Pular para o conteúdo",
           // …
       ],
       image: "assets/og/pt-2x.png",
       localisation: .init(
           searchPlaceholder: "Buscar",
           // … other built-in UI strings; unset ones fall back to English
       )
   )
   

   • Use a built-in LanguageCode if one exists; otherwise .custom(code: "pt", name: "Português"). The code becomes the Markdown file suffix (*.pt.md).
   • For an RTL language, a built-in code like .arabic sets isRTL automatically; for a custom RTL code, check Kiln's LanguageCode API.
2. Add the OG card: drop a 1200×630 (ideally 2400×1260) PNG at docs/4.0/assets/og/pt-2x.png and point image: at it. Omit it and the language falls back to the site-wide card.
3. Translate content. You don't need every page at once — fallback handles gaps — but at minimum do the high-traffic pages (, , ). Create next to each English file, following the AI translation rules. A good AI-assisted flow: iterate over the English files (those without a language suffix), translate each into , and skip ones you're intentionally deferring.

---

Quick checklist for "I changed the docs — cover all languages"

• English content added/edited under docs/4.0/…
• New nav entries added to Version4.swift (English titles)
• navTranslations updated for every language in Languages.swift
• Translated *.<lang>.md created/updated (AI drafts OK, labelled as such)
• Code blocks, links, HTML, admonition keywords left intact in translations
• Frontmatter title/description translated
• (New language only) Language entry, OG card, issue template, design-repo LOCALES
• swift run VaporDocs builds; previewed the affected languages
• PR notes which files are machine-translated; translation-only PRs tagged translation-update

Key files reference

What	Where
English/source content	docs/4.0/<path>.md
A translation	docs/4.0/<path>.<lang>.md
Nav tree (English titles)	Sources/VaporDocs/Version4.swift
Per-language nav titles, UI strings, OG image	Sources/VaporDocs/Languages.swift
Social/OG cards	docs/4.0/assets/og/<code>-2x.png
Translation issue template	.github/translation_needed.description.leaf
Language-suggestion banner	vapor/design → src/js/languageSuggestion.js
Build command	swift run VaporDocs → ./site