Add CChainLockSig::IsNull() and throw an exception in getbestchainlock if there is no known chainlock yet

Author: UdjinM6

src/llmq/quorums_chainlocks.cpp

@@ -23,6 +23,11 @@ static const std::string CLSIG_REQUESTID_PREFIX = "clsig";
 
 CChainLocksHandler* chainLocksHandler;
 
+bool CChainLockSig::IsNull() const
+{
+    return nHeight == -1 && blockHash == uint256();
+}
+
 std::string CChainLockSig::ToString() const
 {
     return strprintf("CChainLockSig(nHeight=%d, blockHash=%s)", nHeight, blockHash.ToString());
@@ -107,7 +112,7 @@ void CChainLocksHandler::ProcessNewChainLock(NodeId from, const llmq::CChainLock
             return;
         }
 
-        if (bestChainLock.nHeight != -1 && clsig.nHeight <= bestChainLock.nHeight) {
+        if (!bestChainLock.IsNull() && clsig.nHeight <= bestChainLock.nHeight) {
             // no need to process/relay older CLSIGs
             return;
         }

src/llmq/quorums_chainlocks.h

@@ -24,7 +24,7 @@ class CChainLockSig
 {
 public:
     int32_t nHeight{-1};
-    uint256 blockHash;
+    uint256 blockHash{uint256()};
     CBLSSignature sig;
 
 public:
@@ -38,6 +38,7 @@ class CChainLockSig
         READWRITE(sig);
     }
 
+    bool IsNull() const;
     std::string ToString() const;
 };
 

src/rpc/blockchain.cpp

@@ -212,7 +212,7 @@ UniValue getbestchainlock(const JSONRPCRequest& request)
     if (request.fHelp || request.params.size() != 0)
         throw std::runtime_error(
             "getbestchainlock\n"
-            "\nReturns the block hash of the best chainlock.\n"
+            "\nReturns the block hash of the best chainlock. Throws an error if there is no known chainlock yet.\n"
             "\nResult:\n"
             "{\n"
             "  \"blockhash\" : \"hash\",      (string) The block hash hex encoded\n"
@@ -225,6 +225,9 @@ UniValue getbestchainlock(const JSONRPCRequest& request)
         );
     UniValue result(UniValue::VOBJ);
     llmq::CChainLockSig clsig = llmq::chainLocksHandler->GetBestChainLock();
+    if (clsig.IsNull()) {
+        throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to find any chainlock");
+    }
     result.push_back(Pair("blockhash", clsig.blockHash.GetHex()));
     result.push_back(Pair("height", clsig.nHeight));
     LOCK(cs_main);