pr24539-suggestion.patch

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index d82e596e60e..396c18c5bf8 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1416,6 +1416,11 @@ static RPCHelpMan gettxspendingprevout()
                     },
                 },
             },
+            {"options", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "",
+                {
+                    {"mempool_only", RPCArg::Type::BOOL, RPCArg::DefaultHint{"true if txospenderindex unavailable, otherwise false"}, "If true, txospenderindex will not be used even if mempool lacks a relevant spend. If false and txospenderindex is unavailable, throws an exception if any outpoint lacks a mempool spend."},
+                },
+                "options"},
         },
         RPCResult{
             RPCResult::Type::ARR, "", "",
@@ -1425,6 +1430,10 @@ static RPCHelpMan gettxspendingprevout()
                     {RPCResult::Type::STR_HEX, "txid", "the transaction id of the checked output"},
                     {RPCResult::Type::NUM, "vout", "the vout value of the checked output"},
                     {RPCResult::Type::STR_HEX, "spendingtxid", /*optional=*/true, "the transaction id of the mempool transaction spending this output (omitted if unspent)"},
+                    {RPCResult::Type::ARR, "warnings", /* optional */ true, "If spendingtxid isn't found in the mempool, and the mempool_only option isn't set explicitly, this will advise of issues using the txospenderindex.",
+                    {
+                        {RPCResult::Type::STR, "", ""},
+                    }},
                 }},
             }
         },
@@ -1440,6 +1449,20 @@ static RPCHelpMan gettxspendingprevout()
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, outputs are missing");
             }
 
+            std::optional<bool> mempool_only;
+            if (!request.params[1].isNull()) {
+                const UniValue& options = request.params[1];
+                RPCTypeCheckObj(options,
+                    {
+                        {"mempool_only", UniValueType(UniValue::VBOOL)},
+                    },
+                    /*fAllowNull=*/true, /*fStrict=*/true);
+
+                if (options.exists("mempool_only")) {
+                    mempool_only = options["mempool_only"].get_bool();
+                }
+            }
+
             std::vector<COutPoint> prevouts;
             prevouts.reserve(output_params.size());
 
@@ -1461,7 +1484,10 @@ static RPCHelpMan gettxspendingprevout()
                 prevouts.emplace_back(txid, nOutput);
             }
 
-            bool f_txospenderindex_ready = g_txospenderindex ? g_txospenderindex->BlockUntilSyncedToCurrentChain() : false;
+            bool f_txospenderindex_ready{false};
+            if (g_txospenderindex && !mempool_only.value_or(false)) {
+                f_txospenderindex_ready = g_txospenderindex->BlockUntilSyncedToCurrentChain();
+            }
 
             const CTxMemPool& mempool = EnsureAnyMemPool(request.context);
             LOCK(mempool.cs);
@@ -1476,13 +1502,29 @@ static RPCHelpMan gettxspendingprevout()
                 const CTransaction* spendingTx = mempool.GetConflictTx(prevout);
                 if (spendingTx != nullptr) {
                     o.pushKV("spendingtxid", spendingTx->GetHash().ToString());
+                } else if (mempool_only.value_or(false)) {
+                    // do nothing
                 } else if (g_txospenderindex) {
                     // no spending tx in mempool, query txospender index
                     uint256 spendingtxid;
                     if(g_txospenderindex->FindSpender(prevout, spendingtxid)) {
                         o.pushKV("spendingtxid", spendingtxid.GetHex());
                     } else if (!f_txospenderindex_ready) {
-                        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "No spending tx for the provided outpoint. Transactions spenders are still in the process of being indexed ");
+                        if (mempool_only.has_value()) {  // NOTE: value is false here
+                            throw JSONRPCError(RPC_MISC_ERROR, "No spending tx for the outpoint %s:%s found, and txospenderindex is still being synced.");
+                        } else {
+                            UniValue warnings(UniValue::VARR);
+                            warnings.push_back("txospenderindex is still being synced.");
+                            o.pushKV("warnings", warnings);
+                        }
+                    }
+                } else {
+                    if (mempool_only.has_value()) {  // NOTE: value is false here
+                        throw JSONRPCError(RPC_MISC_ERROR, "No spending tx for the outpoint %s:%s in mempool, and txospenderindex is unavailable.");
+                    } else {
+                        UniValue warnings(UniValue::VARR);
+                        warnings.push_back("txospenderindex is unavailable.");
+                        o.pushKV("warnings", warnings);
                     }
                 }