rpc: Avoid getchaintxstats invalid results

1 files changed, 20 insertions, 8 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index e785678614..9db5d58cd3 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1645,13 +1645,19 @@ static RPCHelpMan getchaintxstats()
                     RPCResult::Type::OBJ, "", "",
                     {
                         {RPCResult::Type::NUM_TIME, "time", "The timestamp for the final block in the window, expressed in " + UNIX_EPOCH_TIME},
-                        {RPCResult::Type::NUM, "txcount", "The total number of transactions in the chain up to that point"},
+                        {RPCResult::Type::NUM, "txcount", /*optional=*/true,
+                         "The total number of transactions in the chain up to that point, if known. "
+                         "It may be unknown when using assumeutxo."},
                         {RPCResult::Type::STR_HEX, "window_final_block_hash", "The hash of the final block in the window"},
                         {RPCResult::Type::NUM, "window_final_block_height", "The height of the final block in the window."},
                         {RPCResult::Type::NUM, "window_block_count", "Size of the window in number of blocks"},
-                        {RPCResult::Type::NUM, "window_tx_count", /*optional=*/true, "The number of transactions in the window. Only returned if \"window_block_count\" is > 0"},
+                        {RPCResult::Type::NUM, "window_tx_count", /*optional=*/true,
+                         "The number of transactions in the window. "
+                         "Only returned if \"window_block_count\" is > 0 and if txcount exists for the start and end of the window."},
                         {RPCResult::Type::NUM, "window_interval", /*optional=*/true, "The elapsed time in the window in seconds. Only returned if \"window_block_count\" is > 0"},
-                        {RPCResult::Type::NUM, "txrate", /*optional=*/true, "The average rate of transactions per second in the window. Only returned if \"window_interval\" is > 0"},
+                        {RPCResult::Type::NUM, "txrate", /*optional=*/true,
+                         "The average rate of transactions per second in the window. "
+                         "Only returned if \"window_interval\" is > 0 and if window_tx_count exists."},
                     }},
                 RPCExamples{
                     HelpExampleCli("getchaintxstats", "")
@@ -1692,19 +1698,25 @@ static RPCHelpMan getchaintxstats()
 
     const CBlockIndex& past_block{*CHECK_NONFATAL(pindex->GetAncestor(pindex->nHeight - blockcount))};
     const int64_t nTimeDiff{pindex->GetMedianTimePast() - past_block.GetMedianTimePast()};
-    const int nTxDiff = pindex->nChainTx - past_block.nChainTx;
+    const auto window_tx_count{
+        (pindex->nChainTx != 0 && past_block.nChainTx != 0) ? std::optional{pindex->nChainTx - past_block.nChainTx} : std::nullopt,
+    };
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("time", (int64_t)pindex->nTime);
-    ret.pushKV("txcount", (int64_t)pindex->nChainTx);
+    if (pindex->nChainTx) {
+        ret.pushKV("txcount", pindex->nChainTx);
+    }
     ret.pushKV("window_final_block_hash", pindex->GetBlockHash().GetHex());
     ret.pushKV("window_final_block_height", pindex->nHeight);
     ret.pushKV("window_block_count", blockcount);
     if (blockcount > 0) {
-        ret.pushKV("window_tx_count", nTxDiff);
+        if (window_tx_count) {
+            ret.pushKV("window_tx_count", *window_tx_count);
+        }
         ret.pushKV("window_interval", nTimeDiff);
-        if (nTimeDiff > 0) {
-            ret.pushKV("txrate", ((double)nTxDiff) / nTimeDiff);
+        if (nTimeDiff > 0 && window_tx_count) {
+            ret.pushKV("txrate", double(*window_tx_count) / nTimeDiff);
         }
     }