Fix bug in electra withdrawals processing (#4281)

Author: jtraglia

specs/electra/beacon-chain.md

@@ -1114,10 +1114,12 @@ def get_expected_withdrawals(state: BeaconState) -> Tuple[Sequence[Withdrawal],
 
         validator = state.validators[withdrawal.validator_index]
         has_sufficient_effective_balance = validator.effective_balance >= MIN_ACTIVATION_BALANCE
-        has_excess_balance = state.balances[withdrawal.validator_index] > MIN_ACTIVATION_BALANCE
+        total_withdrawn = sum(w.amount for w in withdrawals if w.validator_index == withdrawal.validator_index)
+        balance = state.balances[withdrawal.validator_index] - total_withdrawn
+        has_excess_balance = balance > MIN_ACTIVATION_BALANCE
         if validator.exit_epoch == FAR_FUTURE_EPOCH and has_sufficient_effective_balance and has_excess_balance:
             withdrawable_balance = min(
-                state.balances[withdrawal.validator_index] - MIN_ACTIVATION_BALANCE,
+                balance - MIN_ACTIVATION_BALANCE,
                 withdrawal.amount)
             withdrawals.append(Withdrawal(
                 index=withdrawal_index,
@@ -1134,9 +1136,8 @@ def get_expected_withdrawals(state: BeaconState) -> Tuple[Sequence[Withdrawal],
     for _ in range(bound):
         validator = state.validators[validator_index]
         # [Modified in Electra:EIP7251]
-        partially_withdrawn_balance = sum(
-            withdrawal.amount for withdrawal in withdrawals if withdrawal.validator_index == validator_index)
-        balance = state.balances[validator_index] - partially_withdrawn_balance
+        total_withdrawn = sum(w.amount for w in withdrawals if w.validator_index == validator_index)
+        balance = state.balances[validator_index] - total_withdrawn
         if is_fully_withdrawable_validator(validator, balance, epoch):
             withdrawals.append(Withdrawal(
                 index=withdrawal_index,

tests/core/pyspec/eth2spec/test/electra/block_processing/test_process_withdrawals.py

@@ -748,3 +748,79 @@ def test_partially_withdrawable_validator_compounding_min_minus_one(spec, state)
         partial_withdrawals_indices=[],
     )
     assert state.pending_partial_withdrawals == []
+
+
+@with_electra_and_later
+@spec_state_test
+def test_pending_withdrawals_two_partial_withdrawals_same_validator_1(spec, state):
+    validator_index = 0
+
+    # Initialize a compounding validator
+    set_compounding_withdrawal_credential_with_balance(
+        spec,
+        state,
+        validator_index,
+        effective_balance=spec.Gwei(32_000_000_000),
+        balance=spec.Gwei(33_000_000_000),
+    )
+
+    # Add two pending withdrawals of 1 ETH each to the queue
+    withdrawal = spec.PendingPartialWithdrawal(
+        validator_index=validator_index,
+        amount=spec.Gwei(1_000_000_000),
+        withdrawable_epoch=spec.get_current_epoch(state),
+    )
+    state.pending_partial_withdrawals = [withdrawal, withdrawal]
+
+    # Ensure our two pending withdrawals are there
+    assert len(state.pending_partial_withdrawals) == 2
+
+    yield from run_withdrawals_processing(
+        spec,
+        state,
+        build_empty_execution_payload(spec, state),
+        num_expected_withdrawals=1,
+    )
+
+    # Ensure our two pending withdrawals were processed
+    assert state.pending_partial_withdrawals == []
+    # Ensure the validator's balance is the minimum
+    assert state.balances[validator_index] == spec.MIN_ACTIVATION_BALANCE
+
+
+@with_electra_and_later
+@spec_state_test
+def test_pending_withdrawals_two_partial_withdrawals_same_validator_2(spec, state):
+    validator_index = 0
+
+    # Initialize a compounding validator
+    set_compounding_withdrawal_credential_with_balance(
+        spec,
+        state,
+        validator_index,
+        effective_balance=spec.Gwei(2015_000_000_000),
+        balance=spec.Gwei(2015_000_000_000),
+    )
+
+    # Add two pending withdrawals of 1008 ETH each to the queue
+    withdrawal = spec.PendingPartialWithdrawal(
+        validator_index=validator_index,
+        amount=spec.Gwei(1008_000_000_000),
+        withdrawable_epoch=spec.get_current_epoch(state),
+    )
+    state.pending_partial_withdrawals = [withdrawal, withdrawal]
+
+    # Ensure our two pending withdrawals are there
+    assert len(state.pending_partial_withdrawals) == 2
+
+    yield from run_withdrawals_processing(
+        spec,
+        state,
+        build_empty_execution_payload(spec, state),
+        num_expected_withdrawals=2,
+    )
+
+    # Ensure our two pending withdrawals were processed
+    assert state.pending_partial_withdrawals == []
+    # Ensure the validator's balance is the minimum
+    assert state.balances[validator_index] == spec.MIN_ACTIVATION_BALANCE