next.js

2b11d01a - Fix: Turbopack CSS HMR error when editing an unmounted merged CSS chunk (#94551)

Fix: Turbopack CSS HMR error when editing an unmounted merged CSS chunk (#94551) ### Fixing a bug - [x] Related issues linked using `fixes #74749`. - [x] Tests added (`test/development/css-hmr-unmounted-chunk`) - [x] N/A — removes an erroneous thrown error ### What? In `next dev` with Turbopack, editing a `.module.css` whose component had unmounted threw `Error: No link element found for chunk .../components_<hash>._.css` as an unhandled rejection. The edit **silently failed to apply** — you had to reload the page manually to see it. ### Why? `applyChunkListUpdate` handles chunk updates asymmetrically: `'added'` calls `loadChunkCached` (loads if missing), but `'total'` calls `reloadChunk`, which is rejected when no `<link>` exists. When a lazy / `dynamic(ssr:false)` component unmounts, `unloadChunk` removes its merged-aggregate `<link>` but the chunk list stays subscribed; a later CSS edit emits a `'total'` update for the now-unlinked aggregate → `reloadChunk` rejects → the `'total'` branch discards the promise → unhandled rejection, and the edit never applies. ### How? `reloadChunk` now loads the fresh stylesheet when no `<link>` is present (mirroring the `'added'` branch) instead of rejecting, so the edit applies without a manual reload. Regression test reproduces with a minimal `dynamic(ssr:false)` + 3 `React.lazy` routes fixture (red before — the error is thrown and the edit doesn't apply; green after). Fixes #74749 <!-- NEXT_JS_LLM_PR --> --------- Co-authored-by: Benjamin Woodruff <benjamin.woodruff@vercel.com>