Add anchor argument to transaction creation rpcs

Author: instagibbs

src/rpc/rawtransaction.cpp

@@ -154,6 +154,11 @@ static std::vector<RPCArg> CreateTxDoc()
                         {"data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "A key-value pair. The key must be \"data\", the value is hex-encoded data"},
                     },
                 },
+                {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "",
+                    {
+                        {"anchor", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "Creates an ephemeral anchor. A key-value pair. The key must be \"anchor\", the value is the amount in " + CURRENCY_UNIT},
+                    },
+                },
             },
         },
         {"locktime", RPCArg::Type::NUM, RPCArg::Default{0}, "Raw locktime. Non-0 value also locktime-activates inputs"},

src/rpc/rawtransaction_util.cpp

@@ -104,6 +104,7 @@ CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniVal
     // Duplicate checking
     std::set<CTxDestination> destinations;
     bool has_data{false};
+    bool has_anchor{false};
 
     for (const std::string& name_ : outputs.getKeys()) {
         if (name_ == "data") {
@@ -115,6 +116,16 @@ CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniVal
 
             CTxOut out(0, CScript() << OP_RETURN << data);
             rawTx.vout.push_back(out);
+        } else if (name_ == "anchor") {
+            if (has_anchor) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, duplicate key: anchor");
+            }
+            has_anchor = true;
+            rawTx.nVersion = 3; // Implicitly opts into V3
+            CAmount nAmount = AmountFromValue(outputs[name_]);
+
+            CTxOut out(nAmount, CScript() << OP_TRUE);
+            rawTx.vout.push_back(out);
         } else {
             CTxDestination destination = DecodeDestination(name_);
             if (!IsValidDestination(destination)) {

test/functional/rpc_psbt.py

@@ -18,6 +18,7 @@
     MAX_BIP125_RBF_SEQUENCE,
     WITNESS_SCALE_FACTOR,
     ser_compact_size,
+    tx_from_hex,
 )
 from test_framework.psbt import (
     PSBT,
@@ -29,6 +30,7 @@
     PSBT_IN_HASH256,
     PSBT_OUT_TAP_TREE,
 )
+from test_framework.script import OP_TRUE
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_approx,
@@ -853,5 +855,20 @@ def test_psbt_input_keys(psbt_input, keys):
         assert_equal(self.nodes[0].combinepsbt([psbt1, psbt1]), psbt1)
 
 
+        self.log.info("Test that PSBT can have ephemeral anchor added in rpc")
+        # Fake input to avoid tripping up segwit deserialization error
+        raw_anchor = self.nodes[0].createrawtransaction([{"txid": "ff"*32, "vout": 0}], [{"anchor":"0.00000001"}])
+        anchor_tx = tx_from_hex(raw_anchor)
+
+        assert_equal(anchor_tx.nVersion, 3)
+        assert_equal(len(anchor_tx.vout), 1)
+        assert_equal(anchor_tx.vout[0].nValue, 1)
+        assert_equal(anchor_tx.vout[0].scriptPubKey, bytes([OP_TRUE]))
+
+        psbt_anchor = self.nodes[0].createpsbt([{"txid": "ff"*32, "vout": 0}], [{"anchor":"0.00000001"}])
+        anchor = PSBT.from_base64(psbt_anchor)
+
+        assert_equal(anchor.g.map[0], anchor_tx.serialize())
+
 if __name__ == '__main__':
     PSBTTest().main()