Fix SelectCoinsMinConf to allow instant respends (#3061)

* Modify tests to check for instant respends

This should fail atm...

* Fix SelectCoinsMinConf to allow instant respends

Now tests should pass again.

Author: UdjinM6

src/wallet/wallet.cpp

@@ -2895,6 +2895,8 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, const int nConfMin
         std::sort(vCoins.begin(), vCoins.end(), less_then_denom);
     }
 
+    int nMaxChainLength = std::min(gArgs.GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT), gArgs.GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT));
+
     // try to find nondenom first to prevent unneeded spending of mixed coins
     for (unsigned int tryDenom = tryDenomStart; tryDenom < 2; tryDenom++)
     {
@@ -2908,11 +2910,13 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, const int nConfMin
 
             const CWalletTx *pcoin = output.tx;
 
+            bool fLockedByIS = pcoin->IsLockedByInstantSend();
+
             // if (logCategories != BCLog::NONE) LogPrint(BCLog::SELECTCOINS, "value %s confirms %d\n", FormatMoney(pcoin->vout[output.i].nValue), output.nDepth);
-            if (output.nDepth < (pcoin->IsFromMe(ISMINE_ALL) ? nConfMine : nConfTheirs))
+            if (output.nDepth < (pcoin->IsFromMe(ISMINE_ALL) ? nConfMine : nConfTheirs) && !fLockedByIS)
                 continue;
 
-            if (!mempool.TransactionWithinChainLimit(pcoin->GetHash(), nMaxAncestors))
+            if (!mempool.TransactionWithinChainLimit(pcoin->GetHash(), fLockedByIS ? nMaxChainLength : nMaxAncestors))
                 continue;
 
             int i = output.i;

test/functional/p2p-instantsend.py

@@ -71,6 +71,9 @@ def test_block_doublespend(self):
             assert (res['hash'] != wrong_block)
             # wait for long time only for first node
             timeout = 1
+        # send coins back to the controller node without waiting for confirmations
+        receiver.sendtoaddress(self.nodes[0].getnewaddress(), 0.9, "", "", True)
+        assert_equal(receiver.getwalletinfo()["balance"], 0)
         # mine more blocks
         # TODO: mine these blocks on an isolated node
         self.bump_mocktime(1)
@@ -109,6 +112,9 @@ def test_mempool_doublespend(self):
         for node in self.nodes:
             self.wait_for_instantlock(is_id, node)
         assert_raises_jsonrpc(-5, "No such mempool or blockchain transaction", isolated.getrawtransaction, dblspnd_txid)
+        # send coins back to the controller node without waiting for confirmations
+        receiver.sendtoaddress(self.nodes[0].getnewaddress(), 0.9, "", "", True)
+        assert_equal(receiver.getwalletinfo()["balance"], 0)
 
 if __name__ == '__main__':
     InstantSendTest().main()