feat(consensus): Assert that consensus ended in a valid state after p…

…rocessing a new block

hathor/consensus/block_consensus.py

@@ -47,6 +47,36 @@ def log(cls) -> Any:
 
     def update_consensus(self, block: Block) -> None:
         self.update_voided_info(block)
+        self.assert_valid_consensus(block)
+
+    def assert_valid_consensus(self, block: Block) -> None:
+        """Assert that all transactions confirmed by the block are valid.
+
+        This assertion might be slow because it runs in O(n) where n is number of transactions confirmed
+        by the block."""
+        for tx in block.iter_transactions_in_this_block():
+            self._assert_tx_not_voided(tx)
+
+    def _assert_tx_not_voided(self, tx: BaseTransaction) -> None:
+        tx_meta = tx.get_metadata()
+        # Since this is the last step in the consensus, the conflict resolution has already been resolved.
+        # Hence, at this point, all transactins confirmed by a block must be non-voided.
+        if tx_meta.voided_by:
+            if bool(self.context.consensus.soft_voided_tx_ids & tx_meta.voided_by):
+                return
+            if tx_meta.voided_by == {tx.hash, self._settings.NC_EXECUTION_FAIL_ID}:
+                return
+            for h in tx_meta.voided_by:
+                if h == self._settings.NC_EXECUTION_FAIL_ID:
+                    continue
+                if h == tx.hash:
+                    continue
+                tx2 = tx.storage.get_transaction(h)
+                tx2_meta = tx2.get_metadata()
+                tx2_voided_by: set[bytes] = tx2_meta.voided_by or set()
+                if self._settings.NC_EXECUTION_FAIL_ID in tx2_voided_by:
+                    return
+        assert tx_meta.voided_by is None
 
     def update_voided_info(self, block: Block) -> None:
         """ This method is called only once when a new block arrives.

tests/simulation/base.py

@@ -18,6 +18,8 @@ def setUp(self) -> None:
         self.simulator = Simulator(self.seed_config)
         self.simulator.start()
 
+        self.reactor = self.simulator._clock
+
         print('-'*30)
         print('Simulation seed config:', self.simulator.seed)
         print('-'*30)