Follow-up to #39357, which inlined the Jed language pack into the
bootstrap HTML to fix the code-split translation race (#35330). That
made non-English full-page loads carry ~67KB (gzipped) of pack on every
request since HTML is uncacheable.
This keeps the synchronous-configuration guarantee but moves the pack
to a content-addressed script: spa.html emits
<script src="/language_pack/<lang>/<version>/script.js"> before the
entry bundle, where <version> is a short content hash of the pack file.
The endpoint serves window.__SUPERSET_LANGUAGE_PACK__ = {...} with
Cache-Control: public, max-age=31536000, immutable, so browsers fetch
the pack once per translation change instead of once per page load, and
cache-bust automatically on upgrade (fixing the stale-pack window the
unversioned /language_pack/<lang>/ fetch had under the 1-year
SEND_FILE_MAX_AGE_DEFAULT).
Details:
- English emits no tag and pays nothing.
- A stale version in a cached HTML page still gets current content,
served no-cache so it can't pin under the wrong address.
- Packs provided via COMMON_BOOTSTRAP_OVERRIDES_FUNC still ride the
bootstrap payload and suppress the script tag (spa.html stashes them
on window instead), preserving the historical workaround.
- The endpoint is deliberately unauthenticated: catalogs are static
public repo content with no user data, and must load for anonymous
principals (login page, embedded).
- preamble.ts fallback chain unchanged: bootstrap pack, window global,
then async fetch if the script failed to load.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
