Add nullifier info and fix params check

src/wallet/rpcwallet.cpp

@@ -3641,22 +3641,28 @@ UniValue z_getwitnesscachestats(const UniValue& params, bool fHelp, const CPubKe
     if (!EnsureWalletIsAvailable(fHelp))
         return NullUniValue;
 
-    if (fHelp || params.size() < 1 || params.size() > 2)
+    if (fHelp || params.size() > 0 )
         throw runtime_error(
             "z_getwitnesscachestats\n"
             "\nReturns statistics about the witness cache for zaddrs\n"
             "\nResult:\n"
             "\njson\n"
             "\nExamples:\n"
-            + HelpExampleCli("z_getwitnesscachestats", "456")
-            + HelpExampleRpc("z_getwitnesscachestats", "456")
+            + HelpExampleCli("z_getwitnesscachestats","")
+            + HelpExampleRpc("z_getwitnesscachestats","")
          );
 
     LOCK2(cs_main, pwalletMain->cs_wallet);
     uint32_t nMinDepth = 1;
     uint64_t total_witnesses = 0;
     uint64_t total_zutxos = 0;
+    std::vector<uint256> nullifiers;
+
     for (auto& wtx : pwalletMain->mapWallet) {
+        // add all nullifiers in this tx to our list
+        for (uint32_t i = 0; i < wtx.second.vShieldedSpend.size(); i++) {
+          nullifiers.emplace_back(wtx.second.vShieldedSpend[i].nullifier);
+        }
         if (wtx.second.GetDepthInMainChain() >= nMinDepth) {
             total_zutxos += wtx.second.mapSaplingNoteData.size();
             for (mapSaplingNoteData_t::value_type& item : wtx.second.mapSaplingNoteData) {
@@ -3667,6 +3673,7 @@ UniValue z_getwitnesscachestats(const UniValue& params, bool fHelp, const CPubKe
     }
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("total_witnesses", total_witnesses);
+    ret.pushKV("total_nullifiers", nullifiers.size());
     ret.pushKV("total_zutxos", total_zutxos);
     ret.pushKV("witnesses_cache_size", pwalletMain->nWitnessCacheSize);
     ret.pushKV("max_witnesses_cache_size", (int) WITNESS_CACHE_SIZE);