Merge #16285: rpc: Improve scantxoutset response and help message

bdd6a4f qa: Check scantxoutset result against gettxoutsetinfo (João Barbosa)
fc0c410 rpc: Improve scantxoutset response and help message (João Barbosa)

Pull request description:

  The new response keys `height` and `bestblock` allow the client to know at what point the scan took place.

  The help message now has all the response keys (`result` and `txouts` were missing) and it's improved a bit. Note that `searched_items` key is renamed to `txouts`, considering `scantxoutset` is marked experimental.

ACKs for top commit:
  laanwj:
    ACK bdd6a4f

Tree-SHA512: 6bb7c3464b19857b756b8bc491ab7c58b0d948aad8c005b26ed27c55a1278f5639217e11a315bb505b4f44ebe86f413068c1e539c8a5f7a4007735586cc6443c

Author: laanwj

src/rpc/blockchain.cpp

@@ -2064,17 +2064,21 @@ UniValue scantxoutset(const JSONRPCRequest& request)
                 },
                 RPCResult{
             "{\n"
+            "  \"success\": true|false,         (boolean) Whether the scan was completed\n"
+            "  \"txouts\": n,                   (numeric) The number of unspent transaction outputs scanned\n"
+            "  \"height\": n,                   (numeric) The current block height (index)\n"
+            "  \"bestblock\": \"hex\",            (string) The hash of the block at the tip of the chain\n"
             "  \"unspents\": [\n"
-            "    {\n"
-            "    \"txid\" : \"transactionid\",     (string) The transaction id\n"
-            "    \"vout\": n,                    (numeric) the vout value\n"
-            "    \"scriptPubKey\" : \"script\",    (string) the script key\n"
-            "    \"desc\" : \"descriptor\",        (string) A specialized descriptor for the matched scriptPubKey\n"
-            "    \"amount\" : x.xxx,             (numeric) The total amount in " + CURRENCY_UNIT + " of the unspent output\n"
-            "    \"height\" : n,                 (numeric) Height of the unspent transaction output\n"
+            "   {\n"
+            "    \"txid\": \"hash\",              (string) The transaction id\n"
+            "    \"vout\": n,                   (numeric) The vout value\n"
+            "    \"scriptPubKey\": \"script\",    (string) The script key\n"
+            "    \"desc\": \"descriptor\",        (string) A specialized descriptor for the matched scriptPubKey\n"
+            "    \"amount\": x.xxx,             (numeric) The total amount in " + CURRENCY_UNIT + " of the unspent output\n"
+            "    \"height\": n,                 (numeric) Height of the unspent transaction output\n"
             "   }\n"
-            "   ,...], \n"
-            " \"total_amount\" : x.xxx,          (numeric) The total amount of all found unspent outputs in " + CURRENCY_UNIT + "\n"
+            "   ,...],\n"
+            "  \"total_amount\": x.xxx,          (numeric) The total amount of all found unspent outputs in " + CURRENCY_UNIT + "\n"
             "]\n"
                 },
                 RPCExamples{""},
@@ -2128,15 +2132,20 @@ UniValue scantxoutset(const JSONRPCRequest& request)
         g_scan_progress = 0;
         int64_t count = 0;
         std::unique_ptr<CCoinsViewCursor> pcursor;
+        CBlockIndex* tip;
         {
             LOCK(cs_main);
             ::ChainstateActive().ForceFlushStateToDisk();
             pcursor = std::unique_ptr<CCoinsViewCursor>(::ChainstateActive().CoinsDB().Cursor());
             assert(pcursor);
+            tip = ::ChainActive().Tip();
+            assert(tip);
         }
         bool res = FindScriptPubKey(g_scan_progress, g_should_abort_scan, count, pcursor.get(), needles, coins);
         result.pushKV("success", res);
-        result.pushKV("searched_items", count);
+        result.pushKV("txouts", count);
+        result.pushKV("height", tip->nHeight);
+        result.pushKV("bestblock", tip->GetBlockHash().GetHex());
 
         for (const auto& it : coins) {
             const COutPoint& outpoint = it.first;

test/functional/rpc_scantxoutset.py

@@ -58,6 +58,13 @@ def run_test(self):
         self.start_node(0)
         self.nodes[0].generate(110)
 
+        scan = self.nodes[0].scantxoutset("start", [])
+        info = self.nodes[0].gettxoutsetinfo()
+        assert_equal(scan['success'], True)
+        assert_equal(scan['height'], info['height'])
+        assert_equal(scan['txouts'], info['txouts'])
+        assert_equal(scan['bestblock'], info['bestblock'])
+
         self.restart_node(0, ['-nowallet'])
         self.log.info("Test if we have found the non HD unspent outputs.")
         assert_equal(self.nodes[0].scantxoutset("start", [ "pkh(" + pubk1 + ")", "pkh(" + pubk2 + ")", "pkh(" + pubk3 + ")"])['total_amount'], Decimal("0.002"))