allow send rpc take external inputs and solving data

src/wallet/rpcwallet.cpp

@@ -4286,6 +4286,26 @@ static RPCHelpMan send()
                     },
                     {"replaceable", RPCArg::Type::BOOL, RPCArg::DefaultHint{"wallet default"}, "Marks this transaction as BIP125 replaceable.\n"
                                                   "Allows this transaction to be replaced by a transaction with higher fees"},
+                    {"solving_data", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "Keys and scripts needed for producing a final transaction with a dummy signature.\n"
+                        "Used for fee estimation during coin selection.",
+                        {
+                            {"pubkeys", RPCArg::Type::ARR, RPCArg::Default{UniValue::VARR}, "Public keys involved in this transaction.",
+                                {
+                                    {"pubkey", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, "A public key"},
+                                },
+                            },
+                            {"scripts", RPCArg::Type::ARR, RPCArg::Default{UniValue::VARR}, "Scripts involved in this transaction.",
+                                {
+                                    {"script", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, "A script"},
+                                },
+                            },
+                            {"descriptors", RPCArg::Type::ARR, RPCArg::Default{UniValue::VARR}, "Descriptors that provide solving data for this transaction.",
+                                {
+                                    {"descriptor", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "A descriptor"},
+                                },
+                            }
+                        }
+                    },
                 },
                 "options"},
         },

test/functional/wallet_send.py

@@ -9,6 +9,7 @@ from itertools import product
 
 from test_framework.authproxy import JSONRPCException
 from test_framework.descriptors import descsum_create
+from test_framework.key import ECKey
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -16,6 +17,7 @@ from test_framework.util import (
     assert_greater_than,
     assert_raises_rpc_error,
 )
+from test_framework.wallet_util import bytes_to_wif
 
 class WalletSendTest(BitcoinTestFramework):
     def set_test_params(self):
@@ -35,7 +37,7 @@ class WalletSendTest(BitcoinTestFramework):
                   conf_target=None, estimate_mode=None, fee_rate=None, add_to_wallet=None, psbt=None,
                   inputs=None, add_inputs=None, include_unsafe=None, change_address=None, change_position=None, change_type=None,
                   include_watching=None, locktime=None, lock_unspents=None, replaceable=None, subtract_fee_from_outputs=None,
-                  expect_error=None):
+                  expect_error=None, solving_data=None):
         assert (amount is None) != (data is None)
 
         from_balance_before = from_wallet.getbalances()["mine"]["trusted"]
@@ -94,6 +96,8 @@ class WalletSendTest(BitcoinTestFramework):
             options["replaceable"] = replaceable
         if subtract_fee_from_outputs is not None:
             options["subtract_fee_from_outputs"] = subtract_fee_from_outputs
+        if solving_data is not None:
+            options["solving_data"] = solving_data
 
         if len(options.keys()) == 0:
             options = None
@@ -476,6 +480,46 @@ class WalletSendTest(BitcoinTestFramework):
         res = self.test_send(from_wallet=w5, to_wallet=w0, amount=1, include_unsafe=True)
         assert res["complete"]
 
+        self.log.info("External outputs")
+        eckey = ECKey()
+        eckey.generate()
+        privkey = bytes_to_wif(eckey.get_bytes())
+
+        self.nodes[1].createwallet("extsend")
+        ext_wallet = self.nodes[1].get_wallet_rpc("extsend")
+        self.nodes[1].createwallet("extfund")
+        ext_fund = self.nodes[1].get_wallet_rpc("extfund")
+
+        # Make a weird but signable script. sh(pkh()) descriptor accomplishes this
+        desc = descsum_create("sh(pkh({}))".format(privkey))
+        if self.options.descriptors:
+            res = ext_fund.importdescriptors([{"desc": desc, "timestamp": "now"}])
+        else:
+            res = ext_fund.importmulti([{"desc": desc, "timestamp": "now"}])
+        assert res[0]["success"]
+        addr = self.nodes[0].deriveaddresses(desc)[0]
+        addr_info = ext_fund.getaddressinfo(addr)
+
+        self.nodes[0].sendtoaddress(addr, 10)
+        self.nodes[0].sendtoaddress(ext_wallet.getnewaddress(), 10)
+        self.nodes[0].generate(6)
+        ext_utxo = ext_fund.listunspent(addresses=[addr])[0]
+
+        # An external input without solving data should result in an error
+        self.test_send(from_wallet=ext_wallet, to_wallet=self.nodes[0], amount=15, inputs=[ext_utxo], add_inputs=True, psbt=True, include_watching=True, expect_error=(-4, "Insufficient funds"))
+
+        # But funding should work when the solving data is provided
+        res = self.test_send(from_wallet=ext_wallet, to_wallet=self.nodes[0], amount=15, inputs=[ext_utxo], add_inputs=True, psbt=True, include_watching=True, solving_data={"pubkeys": [addr_info['pubkey']], "scripts": [addr_info["embedded"]["scriptPubKey"]]})
+        signed = ext_wallet.walletprocesspsbt(res["psbt"])
+        signed = ext_fund.walletprocesspsbt(res["psbt"])
+        assert signed["complete"]
+        self.nodes[0].finalizepsbt(signed["psbt"])
+
+        res = self.test_send(from_wallet=ext_wallet, to_wallet=self.nodes[0], amount=15, inputs=[ext_utxo], add_inputs=True, psbt=True, include_watching=True, solving_data={"descriptors": [desc]})
+        signed = ext_wallet.walletprocesspsbt(res["psbt"])
+        signed = ext_fund.walletprocesspsbt(res["psbt"])
+        assert signed["complete"]
+        self.nodes[0].finalizepsbt(signed["psbt"])
 
 if __name__ == '__main__':
     WalletSendTest().main()