turbo-tasks: Fix recomputation loop by allowing cell cleanup on error during recomputation#92725
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… during recomputation Normally, cell cleanup is skipped when a task errors because the error is assumed to be a transient eventual-consistency issue (reading stale inputs). Keeping old cell data avoids "cell no longer exists" errors for dependents. During recomputation (task re-executing without being dirty), however, nothing has changed, so the error is not transient. Skipping cell cleanup in this case leaves stale cells that trigger further recomputations, creating an infinite loop. Fix: allow cell_type_max_index updates and cell data removal to proceed during recomputation even when the result is an error. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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mischnic
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Apr 13, 2026
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Is there any test we could write for this? Forcing a recomputation of an error's task deep in a graph? |
andrewimm
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Apr 15, 2026
… 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) <noreply@anthropic.com>
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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?
task.is_dirty().is_none()at completion time (a recomputing task was not dirty when it started executing).is_recomputationthroughTaskExecutionCompletePrepareResultto bothtask_execution_completed_prepareandtask_execution_completed_cleanup.result.is_ok()/!is_error, extend the condition to also allow cleanup whenis_recomputationis true.This ensures that stale cells produced by a erroring recomputation are cleaned up, breaking the infinite loop.