next.js

a0dd2323 - Simplify turbo-tasks-backend: collapse single-impl traits and remove redundant Arc layers (#93983)

Simplify turbo-tasks-backend: collapse single-impl traits and remove redundant Arc layers (#93983) ### What? Simplifies `turbo-tasks-backend` by removing abstraction layers that each had a single implementation, plus several redundant `Arc` indirections that were no longer load-bearing. **Traits removed / collapsed (each had exactly one implementor):** - **`KeyValueDatabase`** — folded into inherent methods on its only impl, `TurboKeyValueDatabase`. - **`BackingStorage` + `BackingStorageSealed`** — folded into inherent methods on the renamed concrete type `TurboBackingStorage` (was the `KeyValueDatabaseBackingStorage<T>` generic + a type alias). - **`ConcurrentWriteBatch`** — folded into inherent methods on `TurboWriteBatch` (it existed to support an old backend implementation that's gone). - The **`B: BackingStorage` generic parameter** is dropped from `TurboTasksBackend`, `TurboTasksBackendInner`, `ExecuteContextImpl`, and `ChildExecuteContextImpl`. Every instantiation in the workspace already resolved to one concrete type. The only remaining trait in the crate's public role is `Backend` (defined in `turbo-tasks`), which stays — removing it would invert the `turbo-tasks` → backend dependency. **`Arc` indirections removed:** - `TurboKeyValueDatabase.db: Arc<TurboPersistence>` → `TurboPersistence` (the write batch only borrowed it; the clone in `new` was gratuitous). - The `self: &Arc<Self>` receivers and `self.clone()` calls in `run_backend_job`, `idle_start`, and `try_read_task_output` — the deferred/background work reaches the backend through the pinned `turbo_tasks` handle instead, whose `Arc` already keeps the backend alive. - With no remaining sharer, the backend's own `Arc<TurboTasksBackendInner>` and the `TurboTasksBackend` newtype were collapsed: the inner fields now live directly in `TurboTasksBackend`, stored inline in `TurboTasks` (which already shares it via its own `Arc<TurboTasks>`). **Other cleanups surfaced by the above:** - `noop_backing_storage()` is now an empty, read-only instance of the real `TurboPersistence` instead of a separate `NoopKvDb` impl — same concrete type as `turbo_backing_storage()`, so the `Either<…>` wrappers in napi and turbopack-cli go away. - `TurboTasksBackend::backing_storage()` accessor replaced with a focused `invalidate_storage(reason_code)` method, so the backend no longer leaks its storage object. - Dead code removed (`CellDependency::key`, `ExecuteContext::schedule` / `suspending_requested`, the non-stats `execute_with_stats` variant) and feature/test-only items gated behind their corresponding `cfg`. ### Why? The no-op storage work removed the last thing forcing these abstractions to be generic/dynamic, so the single-impl traits and the extra `Arc` layers were pure indirection. This is a self-contained simplification: behavior is unchanged. ### Tradeoff - One `Either`/match in every backing-storage method becomes one `is_empty` atomic load (`Relaxed` `AtomicBool`) in `should_restore` — essentially equivalent. - The backend is now stored inline in `TurboTasks` rather than behind a pointer: one fewer indirection on every backend access, at the cost of a larger `TurboTasks` struct. <!-- NEXT_JS_LLM_PR -->