next.js

24e8c18a - [turbopack] Store TaskDirtyCause in Dirtyness and pass to NativeFunction::span (#94057)

[turbopack] Store TaskDirtyCause in Dirtyness and pass to NativeFunction::span (#94057) ### What? Track the cause of task invalidation in turbo-tasks and surface it to the tracing span when a task executes, so traces can show *why* a task was re-run. A new `task_dirty_cause` Cargo feature gates the storage and parameter plumbing for this information. The existing `trace_task_dirty` feature now depends on it. ### Why? When investigating Turbopack performance and incremental-recompute behavior, traces show which tasks ran but not what invalidated them. Recording the `TaskDirtyCause` on the `turbo_tasks::function` span makes it possible to attribute task re-runs to their triggering change (cell update, output change, collectible change, etc.) directly from a trace. ### How? - Replace `Dirtyness::Dirty(TaskPriority)` with a struct variant `Dirty { parent_priority, cause: TaskDirtyCause }`. The `cause` field is only present when the `task_dirty_cause` feature is enabled. - Move `TaskDirtyCause` from `turbo-tasks-backend` into `turbo-tasks` so the span signature in `turbo-tasks` can reference it. - Replace `OutputChange { task_description }` with `OutputChange { function: FunctionId }`, and add a new `ResolveOutputChange { function: FunctionId }` variant used when the task's output is `OutputValue::Output(_)`. This avoids constructing a `String` for the cause at invalidation time. - `NativeFunction::span` now accepts a feature-gated `cause: Option<&TaskDirtyCause>` argument and records it as a `cause` field on the `turbo_tasks::function` span. The cause is read from the dirty state in `try_start_task_execution` before execution starts. - Split the `trace_task_dirty` feature: the new `task_dirty_cause` feature owns the storage/parameter plumbing, and `trace_task_dirty` now depends on it. This lets consumers opt into the storage cost without the full tracing overhead, and keeps the default build unaffected. Closes PACK- <!-- NEXT_JS_LLM_PR -->