next.js

74cdcde8 - feat(turbopack): add LocalPathOrProjectPath PostCSS config resolution (#91338)

feat(turbopack): add LocalPathOrProjectPath PostCSS config resolution (#91338) ### What? Adds a new `experimental.turbopackLocalPostcssConfig` option and corresponding `PostCssConfigLocation::LocalPathOrProjectPath` variant so Turbopack can resolve `postcss.config.js` starting from the CSS file's directory first, falling back to the project root. Also fixes an issue that surfaces when multiple per-directory `postcss.config.js` files are used: **Evaluate pool asset name collisions** — output file names for the Node.js evaluate pool are now derived from an xxh3 hash of the full module ident rather than the bare file name, so multiple `postcss.config.js` files in different directories no longer collide. ### Why? Currently Turbopack uses `ProjectPathOrLocalPath` which checks the project root first, then falls back to the local directory. This means per-directory `postcss.config.js` files cannot override the root config — the root config always wins. For projects that need different PostCSS transforms in different directories (e.g. a monorepo with multiple apps or style directories), the more specific config should take precedence. ### How? **Turbopack PostCSS resolution** (`turbopack/crates/turbopack-node/src/transforms/postcss.rs`): - Added `PostCssConfigLocation::LocalPathOrProjectPath` enum variant with doc comments on all variants - Refactored `find_config_in_location()` to express the search order as a `Vec<FileSystemPath>` built from a single `match`, making each variant's strategy immediately clear **Evaluate pool asset file naming** (`turbopack/crates/turbopack-node/src/evaluate.rs`): - Replaced file-name-based output path derivation with a deterministic xxh3 hash of the full module ident - Adds `turbo-tasks-hash` dependency to `turbopack-node` - Eliminates name collisions when multiple entries share the same file name (e.g. per-directory `postcss.config.js` files) **Next.js config flag** (`packages/next/src/server/config-shared.ts`, `config-schema.ts`): - Added `experimental.turbopackLocalPostcssConfig: boolean` option (opt-in, default `false`) - Wired through `crates/next-core/src/next_config.rs` → both client and server contexts (`next_client/context.rs`, `next_server/context.rs`) - When `true`, uses `LocalPathOrProjectPath`; when `false`/unset, uses the existing `ProjectPathOrLocalPath` (no behavior change by default) **E2E test** (`test/e2e/app-dir/turbopack-postcss-multiple-configs/`): - Runs in both **Turbopack dev and production modes** — skips webpack only (webpack does not support function-valued PostCSS plugins and the `turbopackLocalPostcssConfig` flag is Turbopack-specific) - 5 style directories, each with its own `postcss.config.js` passing a **unique color option** (`blue`, `purple`, `orange`, `cyan`, `magenta`) to a shared PostCSS plugin, proving that per-directory config resolution produces distinct results rather than all sharing the same transform - Root `postcss.config.js` is a no-op — if only the root config were used, CSS would remain unmodified - Test validates all 15 elements (5 dirs × 3 files) render with CSS module classes - Test collects all CSS (inline `<style>` tags for dev, linked `.css` files for production) and asserts each directory's expected color is present and `color: red` is absent **Documentation** (`docs/01-app/03-api-reference/05-config/01-next-config-js/turbopackLocalPostcssConfig.mdx`, `docs/01-app/03-api-reference/08-turbopack.mdx`): - New dedicated reference page for `experimental.turbopackLocalPostcssConfig` covering usage, behavior table, and a directory-tree example - Added to the experimental options table in the Turbopack API reference ## Test plan - [x] `cargo check -p turbo-tasks-backend` passes - [x] `cargo check -p turbopack-node` and `cargo check -p next-core` pass - [x] E2E test `turbopack-postcss-multiple-configs` validates per-directory PostCSS config resolution across 5 directories with distinct per-directory colors (Turbopack dev and production modes) - [x] Test correctly skips in webpack mode and deployment - [x] Documentation page and experimental options table updated <!-- NEXT_JS_LLM_PR --> --------- Co-authored-by: Claude <noreply@anthropic.com> Co-authored-by: Tobias Koppers <sokra@users.noreply.github.com>