rpc: various fixups for dumptxoutset

- Actually generate an assumeutxo hash and display it
- Add nchaintx to output (necessary for use in chainparams entry)
- Add path of serialized UTXO file to output

src/rpc/blockchain.cpp

@@ -15,10 +15,12 @@
 #include <core_io.h>
 #include <deploymentinfo.h>
 #include <deploymentstatus.h>
+#include <fs.h>
 #include <hash.h>
 #include <index/blockfilterindex.h>
 #include <index/coinstatsindex.h>
 #include <node/blockstorage.h>
+#include <logging/timer.h>
 #include <node/coinstats.h>
 #include <node/context.h>
 #include <node/utxo_snapshot.h>
@@ -2547,6 +2549,8 @@ static RPCHelpMan dumptxoutset()
                     {RPCResult::Type::STR_HEX, "base_hash", "the hash of the base of the snapshot"},
                     {RPCResult::Type::NUM, "base_height", "the height of the base of the snapshot"},
                     {RPCResult::Type::STR, "path", "the absolute path that the snapshot was written to"},
+                    {RPCResult::Type::STR_HEX, "txoutset_hash", "the hash of the UTXO set contents"},
+                    {RPCResult::Type::NUM, "nchaintx", "the number of transactions in the chain up to and including the base block"},
                 }
         },
         RPCExamples{
@@ -2569,7 +2573,8 @@ static RPCHelpMan dumptxoutset()
     FILE* file{fsbridge::fopen(temppath, "wb")};
     CAutoFile afile{file, SER_DISK, CLIENT_VERSION};
     NodeContext& node = EnsureAnyNodeContext(request.context);
-    UniValue result = CreateUTXOSnapshot(node, node.chainman->ActiveChainstate(), afile);
+    UniValue result = CreateUTXOSnapshot(
+        node, node.chainman->ActiveChainstate(), afile, path, temppath);
     fs::rename(temppath, path);
 
     result.pushKV("path", path.u8string());
@@ -2578,10 +2583,15 @@ static RPCHelpMan dumptxoutset()
     };
 }
 
-UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFile& afile)
+UniValue CreateUTXOSnapshot(
+    NodeContext& node,
+    CChainState& chainstate,
+    CAutoFile& afile,
+    const fs::path& path,
+    const fs::path& temppath)
 {
     std::unique_ptr<CCoinsViewCursor> pcursor;
-    CCoinsStats stats{CoinStatsHashType::NONE};
+    CCoinsStats stats{CoinStatsHashType::HASH_SERIALIZED};
     CBlockIndex* tip;
 
     {
@@ -2610,6 +2620,10 @@ UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFil
         CHECK_NONFATAL(tip);
     }
 
+    LOG_TIME_SECONDS(strprintf("writing UTXO snapshot at height %s (%s) to file %s (via %s)",
+        tip->nHeight, tip->GetBlockHash().ToString(),
+        fs::PathToString(path), fs::PathToString(temppath)));
+
     SnapshotMetadata metadata{tip->GetBlockHash(), stats.coins_count, tip->nChainTx};
 
     afile << metadata;
@@ -2635,7 +2649,11 @@ UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFil
     result.pushKV("coins_written", stats.coins_count);
     result.pushKV("base_hash", tip->GetBlockHash().ToString());
     result.pushKV("base_height", tip->nHeight);
-
+    result.pushKV("path", path.u8string());
+    result.pushKV("txoutset_hash", stats.hashSerialized.ToString());
+    // Cast required because univalue doesn't have serialization specified for
+    // `unsigned int`, nChainTx's type.
+    result.pushKV("nchaintx", uint64_t{tip->nChainTx});
     return result;
 }
 

src/rpc/blockchain.h

@@ -7,6 +7,7 @@
 
 #include <consensus/amount.h>
 #include <core_io.h>
+#include <fs.h>
 #include <streams.h>
 #include <sync.h>
 
@@ -65,6 +66,11 @@ CBlockPolicyEstimator& EnsureAnyFeeEstimator(const std::any& context);
  * Helper to create UTXO snapshots given a chainstate and a file handle.
  * @return a UniValue map containing metadata about the snapshot.
  */
-UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFile& afile);
+UniValue CreateUTXOSnapshot(
+    NodeContext& node,
+    CChainState& chainstate,
+    CAutoFile& afile,
+    const fs::path& path,
+    const fs::path& tmppath);
 
 #endif

src/test/util/chainstate.h

@@ -34,7 +34,8 @@ CreateAndActivateUTXOSnapshot(NodeContext& node, const fs::path root, F malleati
     FILE* outfile{fsbridge::fopen(snapshot_path, "wb")};
     CAutoFile auto_outfile{outfile, SER_DISK, CLIENT_VERSION};
 
-    UniValue result = CreateUTXOSnapshot(node, node.chainman->ActiveChainstate(), auto_outfile);
+    UniValue result = CreateUTXOSnapshot(
+        node, node.chainman->ActiveChainstate(), auto_outfile, snapshot_path, snapshot_path);
     BOOST_TEST_MESSAGE(
         "Wrote UTXO snapshot to " << fs::PathToString(snapshot_path.make_preferred()) << ": " << result.write());
 

test/functional/rpc_dumptxoutset.py

@@ -45,6 +45,10 @@ class DumptxoutsetTest(BitcoinTestFramework):
             assert_equal(
                 digest, '7ae82c986fa5445678d2a21453bb1c86d39e47af13da137640c2b1cf8093691c')
 
+        assert_equal(
+            out['txoutset_hash'], 'd4b614f476b99a6e569973bf1c0120d88b1a168076f8ce25691fb41dd1cef149')
+        assert_equal(out['nchaintx'], 101)
+
         # Specifying a path to an existing file will fail.
         assert_raises_rpc_error(
             -8, '{} already exists'.format(FILENAME),  node.dumptxoutset, FILENAME)