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Follow up to #3943 with more withdrawal tests and yet another bugfix.
The PR does also proposes to rename partial_withdrawals_count to processed_partial_withdrawals_count and withdrawals test helper refactor.

The fix

The balance withdrawn upon request, i.e. by processing a pending partial withdrawal, wasn’t taken into account for the sweep. Potential outcome is a validator being considered partially withdrawable while it has no excess balance and effectively is not partially withdrawable.

The proposed fix is simply to check if validator index is already presented in the withdrawals and deduct the already withdrawn balance from the balance considered by the sweep.

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@jtraglia jtraglia left a comment

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Thanks for this! It looks really good.

  • The name processed_partial_withdrawals_count makes sense 👍
  • Good catch on the bug, the fix looks correct to me.
  • The new tests are nice. I see no issues here, just a few questions.

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@ppopth ppopth left a comment

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The idea looks good to me

balance = state.balances[validator_index]
# [Modified in Electra:EIP7251]
partially_withdrawn_balance = sum(
withdrawal.amount for withdrawal in withdrawals if withdrawal.validator_index == validator_index)
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Alternatively, it could iterate over withdrawals[:effective_partial_withdrawals_count] which contains partial withdrawals included during the current run. In cases when there are no withdrawal requests eligible for processing this computation will be a noop. But we can also leave the existing computation in the spec for simplicity and defer possible optimisation to the implementations

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@ppopth ppopth Oct 18, 2024

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What is effective_partial_withdrawals_count? I cannot find its definition.

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@ppopth I think he meant processed_partial_withdrawals_count, the newly renamed variable.

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@mkalinin mkalinin Oct 19, 2024

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effective_partial_withdrawals_count = len(withdrawals) computed before the sweep. processed_partial_withdrawals_count may be greater than that number due to skipped partial withdrawals

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That makes sense then.

Co-authored-by: Justin Traglia <[email protected]>
@jtraglia jtraglia merged commit c060147 into ethereum:dev Oct 30, 2024
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4 participants