Merge bitcoin/bitcoin#18933: rpc: Add submit option to generateblock

fa18504d57 rpc: Add submit option to generateblock (MarcoFalke)
fab9a08e14 refactor: Replace block_hash with block_out (MarcoFalke)

Pull request description:

  When submit is turned off, a block can be generated and returned as hex, to be used for further tests. For example, it can be submitted on a different node, on a different interface (like p2p), or just never submitted and be used for other testing purposes.

ACKs for top commit:
  instagibbs:
    ACK fa18504d57
  TheCharlatan:
    tACK fa18504d57

Tree-SHA512: 1b2ab6b71bb7e155c6482d75f5373f4e77de6446cb16bc2dfd19e7a4075b3a6ad87d7ad7a049a9eed934cb71574acfd27202f54c8bb3b03fac869f2e95db7ee5

src/rpc/client.cpp

@@ -37,6 +37,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "generatetodescriptor", 0, "num_blocks" },
     { "generatetodescriptor", 2, "maxtries" },
     { "generateblock", 1, "transactions" },
+    { "generateblock", 2, "submit" },
     { "getnetworkhashps", 0, "nblocks" },
     { "getnetworkhashps", 1, "height" },
     { "sendtoaddress", 1, "amount" },

src/rpc/mining.cpp

@@ -115,9 +115,9 @@ static RPCHelpMan getnetworkhashps()
     };
 }
 
-static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t& max_tries, uint256& block_hash)
+static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t& max_tries, std::shared_ptr<const CBlock>& block_out, bool process_new_block)
 {
-    block_hash.SetNull();
+    block_out.reset();
     block.hashMerkleRoot = BlockMerkleRoot(block);
 
     while (max_tries > 0 && block.nNonce < std::numeric_limits<uint32_t>::max() && !CheckProofOfWork(block.GetHash(), block.nBits, chainman.GetConsensus()) && !ShutdownRequested()) {
@@ -131,12 +131,14 @@ static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t&
         return true;
     }
 
-    std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(block);
-    if (!chainman.ProcessNewBlock(shared_pblock, /*force_processing=*/true, /*min_pow_checked=*/true, nullptr)) {
+    block_out = std::make_shared<const CBlock>(block);
+
+    if (!process_new_block) return true;
+
+    if (!chainman.ProcessNewBlock(block_out, /*force_processing=*/true, /*min_pow_checked=*/true, nullptr)) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "ProcessNewBlock, block not accepted");
     }
 
-    block_hash = block.GetHash();
     return true;
 }
 
@@ -147,16 +149,15 @@ static UniValue generateBlocks(ChainstateManager& chainman, const CTxMemPool& me
         std::unique_ptr<CBlockTemplate> pblocktemplate(BlockAssembler{chainman.ActiveChainstate(), &mempool}.CreateNewBlock(coinbase_script));
         if (!pblocktemplate.get())
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Couldn't create new block");
-        CBlock *pblock = &pblocktemplate->block;
 
-        uint256 block_hash;
-        if (!GenerateBlock(chainman, *pblock, nMaxTries, block_hash)) {
+        std::shared_ptr<const CBlock> block_out;
+        if (!GenerateBlock(chainman, pblocktemplate->block, nMaxTries, block_out, /*process_new_block=*/true)) {
             break;
         }
 
-        if (!block_hash.IsNull()) {
+        if (block_out) {
             --nGenerate;
-            blockHashes.push_back(block_hash.GetHex());
+            blockHashes.push_back(block_out->GetHash().GetHex());
         }
     }
     return blockHashes;
@@ -295,11 +296,13 @@ static RPCHelpMan generateblock()
                     {"rawtx/txid", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, ""},
                 },
             },
+            {"submit", RPCArg::Type::BOOL, RPCArg::Default{true}, "Whether to submit the block before the RPC call returns or to return it as hex."},
         },
         RPCResult{
             RPCResult::Type::OBJ, "", "",
             {
                 {RPCResult::Type::STR_HEX, "hash", "hash of generated block"},
+                {RPCResult::Type::STR_HEX, "hex", /*optional=*/true, "hex of generated block, only present when submit=false"},
             }
         },
         RPCExamples{
@@ -348,6 +351,7 @@ static RPCHelpMan generateblock()
         }
     }
 
+    const bool process_new_block{request.params[2].isNull() ? true : request.params[2].get_bool()};
     CBlock block;
 
     ChainstateManager& chainman = EnsureChainman(node);
@@ -376,15 +380,20 @@ static RPCHelpMan generateblock()
         }
     }
 
-    uint256 block_hash;
+    std::shared_ptr<const CBlock> block_out;
     uint64_t max_tries{DEFAULT_MAX_TRIES};
 
-    if (!GenerateBlock(chainman, block, max_tries, block_hash) || block_hash.IsNull()) {
+    if (!GenerateBlock(chainman, block, max_tries, block_out, process_new_block) || !block_out) {
         throw JSONRPCError(RPC_MISC_ERROR, "Failed to make block.");
     }
 
     UniValue obj(UniValue::VOBJ);
-    obj.pushKV("hash", block_hash.GetHex());
+    obj.pushKV("hash", block_out->GetHash().GetHex());
+    if (!process_new_block) {
+        CDataStream block_ser{SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags()};
+        block_ser << *block_out;
+        obj.pushKV("hex", HexStr(block_ser));
+    }
     return obj;
 },
     };

test/functional/rpc_generate.py

@@ -29,8 +29,13 @@ class RPCGenerateTest(BitcoinTestFramework):
         node = self.nodes[0]
         miniwallet = MiniWallet(node)
 
-        self.log.info('Generate an empty block to address')
+        self.log.info('Mine an empty block to address and return the hex')
         address = miniwallet.get_address()
+        generated_block = self.generateblock(node, output=address, transactions=[], submit=False)
+        node.submitblock(hexdata=generated_block['hex'])
+        assert_equal(generated_block['hash'], node.getbestblockhash())
+
+        self.log.info('Generate an empty block to address')
         hash = self.generateblock(node, output=address, transactions=[])['hash']
         block = node.getblock(blockhash=hash, verbose=2)
         assert_equal(len(block['tx']), 1)