Mempool preconfs: Cleanup contract_users only after rollback

[Dentosal]

See #3264 (comment)

Description

Problem

on_removed_transaction was called for both block-committed transactions and pool evictions, which meant contract_users entries were cleaned up before rollback_preconfirmed_transaction could use them to find and evict dependent pool transactions.

Solution

Add on_committed_transaction (same as on_removed_transaction but skips the Input::Contract cleanup) and remove_from_contract_users (only the Input::Contract cleanup) to the CollisionManager trait and BasicCollisionManager. Block-commitment paths in pool.rs now use on_committed_transaction and return the removed pool transactions to their callers. pool_worker.rs defers remove_from_contract_users until after all preconfirmation rollback for the relevant block height is complete. This ensures rollback always observes the full set of contract dependents.

Checklist

• Breaking changes are clearly marked as such in the PR description and changelog
• New behavior is reflected in tests
• The specification matches the implemented behavior (link update PR if changes are needed)

Before requesting review

• I have reviewed the code myself
• I have created follow-up issues caused by this PR and linked them here

[cursor]

PR Summary

Medium Risk
Touches txpool commit/removal flow and collision-manager bookkeeping; incorrect ordering could leave stale contract_users entries or break rollback-driven evictions.

Overview
Fixes a preconfirmation rollback bug by splitting tx removal handling into committed vs evicted paths so contract_users entries remain available during rollback.

The CollisionManager API gains on_committed_transaction (removal without contract_users cleanup) and remove_from_contract_users (deferred contract-user cleanup), with BasicCollisionManager implementing the new behavior. pool.rs commit paths now use the committed variant and return removed pool transactions, and pool_worker.rs defers contract_users cleanup until after rollback reconciliation per tentative height (and after canonical-block processing).

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Near-duplicate functions risk diverging during future maintenance

Low Severity

update_components_and_caches_on_committed is a near-exact copy of update_components_and_caches_on_removal, differing only in whether on_committed_transaction or on_removed_transaction is called on the collision manager. If future maintenance adds or changes a step in one function but not the other, it will silently introduce a bug. A single shared helper parameterized by which collision-manager method to invoke would eliminate this duplication.

Additional Locations (1)

• crates/services/txpool_v2/src/pool.rs#L853-L870

 

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