From df934990d7bb70a319d245c6d145f8e289ed3046 Mon Sep 17 00:00:00 2001
From: Ori Newman <orinewman1@gmail.com>
Date: Tue, 7 Apr 2020 12:45:12 +0300
Subject: [PATCH] [NOD-822] Don't return rule errors from utxoset code (#693)

* [NOD-822] Remove rule errors from the UTXO diff code

* [NOD-822] Rename applyTransactions -> applyAndVerifyBlockTransactionsToPastUTXO

* [NOD-822] Fix comment
---
 blockdag/dag.go     | 17 +++++++++--------
 blockdag/utxoset.go | 19 ++++++++++---------
 2 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/blockdag/dag.go b/blockdag/dag.go
index 00dbc949a..ee117f3b7 100644
--- a/blockdag/dag.go
+++ b/blockdag/dag.go
@@ -1058,11 +1058,16 @@ func (dag *BlockDAG) meldVirtualUTXO(newVirtualUTXODiffSet *DiffUTXOSet) error {
 	return newVirtualUTXODiffSet.meldToBase()
 }
 
-func (node *blockNode) diffFromTxs(pastUTXO UTXOSet, transactions []*util.Tx) (*UTXODiff, error) {
+// applyAndVerifyBlockTransactionsToPastUTXO applies a block's transactions to its
+// given past UTXO, and verifies that there are no double spends with its past.
+func applyAndVerifyBlockTransactionsToPastUTXO(pastUTXO UTXOSet, blockTransactions []*util.Tx) (UTXOSet, error) {
 	diff := NewUTXODiff()
 
-	for _, tx := range transactions {
+	for _, tx := range blockTransactions {
 		txDiff, err := pastUTXO.diffFromTx(tx.MsgTx(), UnacceptedBlueScore)
+		if errors.Is(err, errUTXOMissingTxOut) {
+			return nil, ruleError(ErrMissingTxOut, err.Error())
+		}
 		if err != nil {
 			return nil, err
 		}
@@ -1072,7 +1077,7 @@ func (node *blockNode) diffFromTxs(pastUTXO UTXOSet, transactions []*util.Tx) (*
 		}
 	}
 
-	return diff, nil
+	return pastUTXO.WithDiff(diff)
 }
 
 // verifyAndBuildUTXO verifies all transactions in the given block and builds its UTXO
@@ -1096,11 +1101,7 @@ func (node *blockNode) verifyAndBuildUTXO(dag *BlockDAG, transactions []*util.Tx
 		return nil, nil, nil, nil, err
 	}
 
-	diffFromTxs, err := node.diffFromTxs(pastUTXO, transactions)
-	if err != nil {
-		return nil, nil, nil, nil, err
-	}
-	utxo, err := pastUTXO.WithDiff(diffFromTxs)
+	utxo, err := applyAndVerifyBlockTransactionsToPastUTXO(pastUTXO, transactions)
 	if err != nil {
 		return nil, nil, nil, nil, err
 	}
diff --git a/blockdag/utxoset.go b/blockdag/utxoset.go
index f56f6801d..eb5a134c2 100644
--- a/blockdag/utxoset.go
+++ b/blockdag/utxoset.go
@@ -293,8 +293,8 @@ func (d *UTXODiff) withDiffInPlace(diff *UTXODiff) error {
 		}
 		if d.toRemove.contains(outpoint) {
 			// If already exists - this is an error
-			return ruleError(ErrWithDiff, fmt.Sprintf(
-				"withDiffInPlace: outpoint %s both in d.toRemove and in diff.toRemove", outpoint))
+			return errors.Errorf(
+				"withDiffInPlace: outpoint %s both in d.toRemove and in diff.toRemove", outpoint)
 		}
 
 		// If not exists neither in toAdd nor in toRemove - add to toRemove
@@ -305,9 +305,9 @@ func (d *UTXODiff) withDiffInPlace(diff *UTXODiff) error {
 		if d.toRemove.containsWithBlueScore(outpoint, entryToAdd.blockBlueScore) {
 			// If already exists in toRemove with the same blueScore - remove from toRemove
 			if d.toAdd.contains(outpoint) && !diff.toRemove.contains(outpoint) {
-				return ruleError(ErrWithDiff, fmt.Sprintf(
+				return errors.Errorf(
 					"withDiffInPlace: outpoint %s both in d.toAdd and in diff.toAdd with no "+
-						"corresponding entry in diff.toRemove", outpoint))
+						"corresponding entry in diff.toRemove", outpoint)
 			}
 			d.toRemove.remove(outpoint)
 			continue
@@ -316,8 +316,8 @@ func (d *UTXODiff) withDiffInPlace(diff *UTXODiff) error {
 			(existingEntry.blockBlueScore == entryToAdd.blockBlueScore ||
 				!diff.toRemove.containsWithBlueScore(outpoint, existingEntry.blockBlueScore)) {
 			// If already exists - this is an error
-			return ruleError(ErrWithDiff, fmt.Sprintf(
-				"withDiffInPlace: outpoint %s both in d.toAdd and in diff.toAdd", outpoint))
+			return errors.Errorf(
+				"withDiffInPlace: outpoint %s both in d.toAdd and in diff.toAdd", outpoint)
 		}
 
 		// If not exists neither in toAdd nor in toRemove, or exists in toRemove with different blueScore - add to toAdd
@@ -406,6 +406,8 @@ type UTXOSet interface {
 	Get(outpoint wire.Outpoint) (*UTXOEntry, bool)
 }
 
+var errUTXOMissingTxOut = errors.New("missing transaction output in the utxo set")
+
 // diffFromTx is a common implementation for diffFromTx, that works
 // for both diff-based and full UTXO sets
 // Returns a diff that is equivalent to provided transaction,
@@ -421,9 +423,8 @@ func diffFromTx(u UTXOSet, tx *wire.MsgTx, acceptingBlueScore uint64) (*UTXODiff
 					return nil, err
 				}
 			} else {
-				return nil, ruleError(ErrMissingTxOut, fmt.Sprintf(
-					"Transaction %s is invalid because spends outpoint %s that is not in utxo set",
-					tx.TxID(), txIn.PreviousOutpoint))
+				return nil, errors.Wrapf(errUTXOMissingTxOut, "Transaction %s is invalid because it spends "+
+					"outpoint %s that is not in utxo set", tx.TxID(), txIn.PreviousOutpoint)
 			}
 		}
 	}