0c4d2648b5
This PR fixes issues with flaky cancellation_empty_by test. The original test gated the runner's `waitFor: blocked` on `t1`'s `wait_for_cancel_once_async`, which had no causal relationship to `tracerSuggestion` having actually run inside the empty-`by` snapshot task. On CI under load the runner could trigger the insert before `tracerSuggestion` registered its `onSet` callback, leading to intermittent timeouts. Add a label-keyed `IO.Promise` registry (`syncPromisesRef`) plus `getSyncPromise` / `resolveSyncPromise` primitives and a `wait_for_sync <label>` tactic to `Lean.Server.Test.Cancel`. The empty-`by` test's `tracerSuggestion` now resolves a sync promise after registering its onSet, and `t1` waits on that promise before emitting `blocked`. The empty-`by` example must precede `t1` because `try?` inside the snapshot task synchronously waits on prior pending async theorem bodies during library search (likely a separate upstream issue); with that ordering the test is fully deterministic. `t1` also drops `wait_for_cancel_once_async` in favor of plain `trace "blocked"`. The test now also `dbg_trace`s at each sync point (`tracerSuggestion ready`, `sync received`, `cancelTokenSet`) so the .out.expected captures the deterministic execution sequence. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
73 lines
2.5 KiB
Text
73 lines
2.5 KiB
Text
import Lean.Server.Test.Cancel
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import Lean.Elab.Tactic.Try
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open Lean Lean.Meta Lean.Elab Lean.Elab.Term Lean.Elab.Tactic
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open Lean.Server.Test.Cancel
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/-!
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Test that `cancelRec` reaches the snapshot task spawned by
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`elabEmptyByAsTry` on re-elaboration.
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Chronological flow:
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1. Empty-`by` example elaborates; `elabEmptyByAsTry` spawns a snapshot
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task with its own cancel token and returns.
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2. The snapshot task's `try?` calls `tracerSuggestion`, which:
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- registers test task `"cancelTokenSet"`,
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- registers `cancelTk.onSet` to resolve it,
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- resolves sync promise `"tracerSuggestion"`,
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- returns `wait_for_test_task "cancelTokenSet"` as the candidate.
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3. `try?` evaluates the candidate; it blocks on the test task.
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4. `t1` elaborates: `wait_for_sync "tracerSuggestion"` returns
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immediately, `trace "blocked"` emits the diagnostic.
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5. Runner inserts `; skip`, triggers re-elab; `cancelRec` sets the
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cancel token; `onSet` resolves the test task; the candidate's wait
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returns; the snapshot task body completes.
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Failure modes:
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- `cancelTk? := none` to `Core.logSnapshotTask`: `cancelRec` cannot
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reach the cancel token, the wait blocks, runner times out.
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- `cancelTk? := none` to `wrapAsyncAsSnapshot`: `tracerSuggestion`
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sees no cancel token, doesn't register `onSet`; the promise drops;
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`wait_for_test_task` surfaces a `task dropped` diagnostic.
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Ordering note: the empty-`by` example must precede `t1` because `try?`
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inside the snapshot task library-searches the environment in a way
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that synchronously waits on prior pending async theorem bodies. With
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`t1` first, its `wait_for_sync` would block the snapshot's `try?`,
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deadlocking. Likely a separate upstream issue.
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-/
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namespace TestEmptyBy
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opaque UnsolvableProp : Prop
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@[try_suggestion]
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def tracerSuggestion (_goal : MVarId) (_info : Try.Info) :
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MetaM (Array (TSyntax `tactic)) := do
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if let some prom ← mkTestTask "cancelTokenSet" then
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if let some cancelTk := (← readThe Core.Context).cancelTk? then
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cancelTk.onSet (do
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dbg_trace "cancelTokenSet"
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prom.resolve ())
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dbg_trace "tracerSuggestion ready"
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resolveSyncPromise "tracerSuggestion"
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return #[← `(tactic| wait_for_test_task "cancelTokenSet")]
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end TestEmptyBy
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set_option tactic.tryOnEmptyBy true
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example : True := by
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trivial
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--^ waitFor: blocked
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--^ insert: "; skip"
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--^ sync
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example : TestEmptyBy.UnsolvableProp := by
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theorem t1 : True := by
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wait_for_sync "tracerSuggestion"
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dbg_trace "sync received"
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trace "blocked"
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trivial
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