re-proven withdrawals (#9471)

indexer/database/bridge_transactions.go

@@ -188,10 +188,11 @@ func (db *bridgeTransactionsDB) MarkL2TransactionWithdrawalProvenEvent(withdrawa
 
 	if withdrawal.ProvenL1EventGUID != nil && withdrawal.ProvenL1EventGUID.ID() == provenL1EventGuid.ID() {
 		return nil
-	} else if withdrawal.ProvenL1EventGUID != nil {
-		return fmt.Errorf("proven withdrawal %s re-proven with a different event %s", withdrawalHash, provenL1EventGuid)
 	}
 
+	// Withdrawals can be re-proven in the event that the claim they were proven against was successfully
+	// challenged. Rather than track each individual dispute game, we allow the proven event to simply be
+	// overwritten.
 	withdrawal.ProvenL1EventGUID = &provenL1EventGuid
 	result := db.gorm.Save(&withdrawal)
 	return result.Error

indexer/migrations/20230523_create_schema.sql

@@ -119,7 +119,10 @@ CREATE TABLE IF NOT EXISTS l2_transaction_withdrawals (
     nonce                   UINT256 NOT NULL UNIQUE,
     initiated_l2_event_guid VARCHAR NOT NULL UNIQUE REFERENCES l2_contract_events(guid) ON DELETE CASCADE,
 
-    -- Multistep (bedrock) process of a withdrawal
+    -- Multistep (bedrock) process of a withdrawal. With permissionless-output proposals, `proven_l1_event_guid`
+    -- should be treated as the last known proven event. It may be the case (rare) that the proven state of this
+    -- withdrawal was invalidated via a fault proof. This case is considered "rare" a malicious outputs are
+    -- disincentivezed via the posted bond.
     proven_l1_event_guid    VARCHAR UNIQUE REFERENCES l1_contract_events(guid) ON DELETE SET NULL ON UPDATE CASCADE,
     finalized_l1_event_guid VARCHAR UNIQUE REFERENCES l1_contract_events(guid) ON DELETE SET NULL ON UPDATE CASCADE,
     succeeded               BOOLEAN,

indexer/processors/bridge/l1_bridge_processor.go

@@ -170,6 +170,10 @@ func L1ProcessFinalizedBridgeEvents(log log.Logger, db *database.DB, metrics L1M
 			return fmt.Errorf("missing indexed withdrawal! tx_hash = %s", provenWithdrawal.Event.TransactionHash)
 		}
 
+		if withdrawal.ProvenL1EventGUID != nil && withdrawal.ProvenL1EventGUID.ID() != provenWithdrawals[i].Event.GUID.ID() {
+			log.Info("detected re-proven withdrawal", "tx_hash", provenWithdrawal.Event.TransactionHash.String())
+		}
+
 		if err := db.BridgeTransactions.MarkL2TransactionWithdrawalProvenEvent(provenWithdrawal.WithdrawalHash, provenWithdrawals[i].Event.GUID); err != nil {
 			return fmt.Errorf("failed to mark withdrawal as proven. tx_hash = %s: %w", provenWithdrawal.Event.TransactionHash, err)
 		}