gettxoutproof() should return consistent result

We can call gettxoutproof() with a list of transactions. Currently, if
the first transaction is unspent (and all other transactions are in the
same block), then the call will succeed. If the first transaction has
been spent, then the call will fail. The means that the following two
calls will return different results:

gettxoutproof(unspent_tx1, spent_tx1)
gettxoutproof(spent_tx1, unspent_tx1)

This commit makes behaviour independent of transaction ordering by looping
through all transactions provided and trying to find which block they're in.

This commit also increases the test coverage and tests more failure
cases for gettxoutproof()

1 files changed, 8 insertions, 4 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index e27c2a77c7..fe56519e74 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -219,9 +219,13 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         pblockindex = mapBlockIndex[hashBlock];
     } else {
-        const Coin& coin = AccessByTxid(*pcoinsTip, oneTxid);
-        if (!coin.IsSpent() && coin.nHeight > 0 && coin.nHeight <= chainActive.Height()) {
-            pblockindex = chainActive[coin.nHeight];
+        // Loop through txids and try to find which block they're in. Exit loop once a block is found.
+        for (const auto& tx : setTxids) {
+            const Coin& coin = AccessByTxid(*pcoinsTip, tx);
+            if (!coin.IsSpent()) {
+                pblockindex = chainActive[coin.nHeight];
+                break;
+            }
         }
     }
 
@@ -244,7 +248,7 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
         if (setTxids.count(tx->GetHash()))
             ntxFound++;
     if (ntxFound != setTxids.size())
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "(Not all) transactions not found in specified block");
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Not all transactions found in specified or retrieved block");
 
     CDataStream ssMB(SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS);
     CMerkleBlock mb(block, setTxids);