turbo-tasks: Fix recomputation loop by allowing cell cleanup on error during recomputation (#92725)

### What?

Fix an infinite recomputation loop in turbo-tasks by allowing cell
cleanup to proceed during recomputation even when the task result is an
error.

### Why?

When a task errors during normal execution, cell cleanup is
intentionally skipped. The rationale is that errors during normal
execution are often transient eventual-consistency issues caused by
reading stale inputs — keeping old cell data prevents "cell no longer
exists" errors for dependent tasks that are reading those cells.

However, during **recomputation** (a task re-executing without being
marked dirty), nothing about its inputs has changed. Any error it
produces is therefore not transient. If cell cleanup is skipped in this
case, stale cells remain in place, which trigger further recomputations,
which produce further errors, which skip further cleanups — creating an
infinite loop.

### How?

- Detect whether a task execution is a recomputation by checking
`task.is_dirty().is_none()` at completion time (a recomputing task was
not dirty when it started executing).
- Propagate `is_recomputation` through
`TaskExecutionCompletePrepareResult` to both
`task_execution_completed_prepare` and
`task_execution_completed_cleanup`.
- In both places where cell cleanup is gated on `result.is_ok()` /
`!is_error`, extend the condition to also allow cleanup when
`is_recomputation` is true.

This ensures that stale cells produced by a erroring recomputation are
cleaned up, breaking the infinite loop.

<!-- NEXT_JS_LLM_PR -->

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

turbopack/crates/turbo-tasks-backend/src/backend/mod.rs

@@ -450,6 +450,7 @@ struct TaskExecutionCompletePrepareResult {
     pub no_output_set: bool,
     pub new_output: Option<OutputValue>,
     pub output_dependent_tasks: SmallVec<[TaskId; 4]>,
+    pub is_recomputation: bool,
 }
 
 // Operations
@@ -2056,6 +2057,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
             no_output_set,
             new_output,
             output_dependent_tasks,
+            is_recomputation,
         }) = self.task_execution_completed_prepare(
             &mut ctx,
             #[cfg(feature = "trace_task_details")]
@@ -2122,8 +2124,13 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
             return true;
         }
 
-        let removed_data =
-            self.task_execution_completed_cleanup(&mut ctx, task_id, cell_counters, is_error);
+        let removed_data = self.task_execution_completed_cleanup(
+            &mut ctx,
+            task_id,
+            cell_counters,
+            is_error,
+            is_recomputation,
+        );
 
         // Drop data outside of critical sections
         drop(removed_data);
@@ -2143,6 +2150,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
         has_invalidator: bool,
     ) -> Option<TaskExecutionCompletePrepareResult> {
         let mut task = ctx.task(task_id, TaskDataCategory::All);
+        let is_recomputation = task.is_dirty().is_none();
         let Some(in_progress) = task.get_in_progress_mut() else {
             panic!("Task execution completed, but task is not in progress: {task:#?}");
         };
@@ -2154,6 +2162,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
                 no_output_set: false,
                 new_output: None,
                 output_dependent_tasks: Default::default(),
+                is_recomputation,
             });
         }
         let &mut InProgressState::InProgress(box InProgressStateInner {
@@ -2224,7 +2233,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
         // that data is correct.
         // NOTE: This must stay in sync with task_execution_completed_cleanup, which similarly
         // skips cell data removal on error.
-        if result.is_ok() {
+        if result.is_ok() || is_recomputation {
             let old_counters: FxHashMap<_, _> = task
                 .iter_cell_type_max_index()
                 .map(|(&k, &v)| (k, v))
@@ -2386,6 +2395,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
             no_output_set,
             new_output,
             output_dependent_tasks,
+            is_recomputation,
         })
     }
 
@@ -2694,6 +2704,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
         task_id: TaskId,
         cell_counters: &AutoMap<ValueTypeId, u32, BuildHasherDefault<FxHasher>, 8>,
         is_error: bool,
+        is_recomputation: bool,
     ) -> Vec<SharedReference> {
         let mut task = ctx.task(task_id, TaskDataCategory::All);
         let mut removed_cell_data = Vec::new();
@@ -2702,7 +2713,7 @@ impl<B: BackingStorage> TurboTasksBackendInner<B> {
         // clean to avoid re-executions.
         // NOTE: This must stay in sync with task_execution_completed_prepare, which similarly
         // skips cell_type_max_index updates on error.
-        if !is_error {
+        if !is_error || is_recomputation {
             // Remove no longer existing cells and
             // find all outdated data items (removed cells, outdated edges)
             // Note: We do not mark the tasks as dirty here, as these tasks are unused or stale