Merge #14410: rpcwallet: 'ischange' field for 'getaddressinfo' RPC

14a06525b2 tests: add test for 'getaddressinfo' RPC result 'ischange' field (whythat)
93d1aa9abc rpcwallet: add 'ischange' field to 'getaddressinfo' response (whythat)

Pull request description:

  Implementation of proposal in #14396.

  This introduces `CWallet::IsChange(CScript&)` method and replaces original `CWallet::IsChange(CTxOut&)` method with overloaded version that delegates to the new method with *txout*'s `scriptPubKey`. In this way `TODO` note from the original method can still be addressed in a single place.

Tree-SHA512: ef5dbc82d76b4b9b2fa6a70abc3385a677c55021f79e187ee2f392ee32bc6b406191f4129acae5c17b0206e72b6712e7e0cad574a4bbd966871c2e656c45e041

doc/release-notes-14282.md

@@ -4,3 +4,6 @@ Low-level RPC changes
 `-usehd` was removed in version 0.16. From that version onwards, all new
 wallets created are hierarchical deterministic wallets. Version 0.18 makes
 specifying `-usehd` invalid config.
+
+`ischange` field of boolean type that shows if an address was used for change
+output was added to `getaddressinfo` method response.

src/wallet/rpcwallet.cpp

@@ -3458,6 +3458,7 @@ UniValue getaddressinfo(const JSONRPCRequest& request)
             "  \"solvable\" : true|false,      (boolean) If the address is solvable by the wallet\n"
             "  \"iswatchonly\" : true|false,   (boolean) If the address is watchonly\n"
             "  \"isscript\" : true|false,      (boolean) If the key is a script\n"
+            "  \"ischange\" : true|false,      (boolean) If the address was used for change output\n"
             "  \"iswitness\" : true|false,     (boolean) If the address is a witness address\n"
             "  \"witness_version\" : version   (numeric, optional) The version number of the witness program\n"
             "  \"witness_program\" : \"hex\"     (string, optional) The hex value of the witness program\n"
@@ -3516,6 +3517,7 @@ UniValue getaddressinfo(const JSONRPCRequest& request)
     if (pwallet->mapAddressBook.count(dest)) {
         ret.pushKV("label", pwallet->mapAddressBook[dest].name);
     }
+    ret.pushKV("ischange", pwallet->IsChange(scriptPubKey));
     const CKeyMetadata* meta = nullptr;
     CKeyID key_id = GetKeyForDestination(*pwallet, dest);
     if (!key_id.IsNull()) {

src/wallet/wallet.cpp

@@ -1261,6 +1261,11 @@ CAmount CWallet::GetCredit(const CTxOut& txout, const isminefilter& filter) cons
 }
 
 bool CWallet::IsChange(const CTxOut& txout) const
+{
+    return IsChange(txout.scriptPubKey);
+}
+
+bool CWallet::IsChange(const CScript& script) const
 {
     // TODO: fix handling of 'change' outputs. The assumption is that any
     // payment to a script that is ours, but is not in the address book
@@ -1269,10 +1274,10 @@ bool CWallet::IsChange(const CTxOut& txout) const
     // a better way of identifying which outputs are 'the send' and which are
     // 'the change' will need to be implemented (maybe extend CWalletTx to remember
     // which output, if any, was change).
-    if (::IsMine(*this, txout.scriptPubKey))
+    if (::IsMine(*this, script))
     {
         CTxDestination address;
-        if (!ExtractDestination(txout.scriptPubKey, address))
+        if (!ExtractDestination(script, address))
             return true;
 
         LOCK(cs_wallet);

src/wallet/wallet.h

@@ -971,6 +971,7 @@ public:
     isminetype IsMine(const CTxOut& txout) const;
     CAmount GetCredit(const CTxOut& txout, const isminefilter& filter) const;
     bool IsChange(const CTxOut& txout) const;
+    bool IsChange(const CScript& script) const;
     CAmount GetChange(const CTxOut& txout) const;
     bool IsMine(const CTransaction& tx) const;
     /** should probably be renamed to IsRelevantToMe */

test/functional/wallet_basic.py

@@ -479,7 +479,7 @@ class WalletTest(BitcoinTestFramework):
         # Verify nothing new in wallet
         assert_equal(total_txs, len(self.nodes[0].listtransactions("*", 99999)))
 
-        # Test getaddressinfo. Note that these addresses are taken from disablewallet.py
+        # Test getaddressinfo on external address. Note that these addresses are taken from disablewallet.py
         assert_raises_rpc_error(-5, "Invalid address", self.nodes[0].getaddressinfo, "3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy")
         address_info = self.nodes[0].getaddressinfo("mneYUmWYsuk7kySiURxCi3AGxrAqZxLgPZ")
         assert_equal(address_info['address'], "mneYUmWYsuk7kySiURxCi3AGxrAqZxLgPZ")
@@ -487,6 +487,22 @@ class WalletTest(BitcoinTestFramework):
         assert not address_info["ismine"]
         assert not address_info["iswatchonly"]
         assert not address_info["isscript"]
+        assert not address_info["ischange"]
+
+        # Test getaddressinfo 'ischange' field on change address.
+        self.nodes[0].generate(1)
+        destination = self.nodes[1].getnewaddress()
+        txid = self.nodes[0].sendtoaddress(destination, 0.123)
+        tx = self.nodes[0].decoderawtransaction(self.nodes[0].getrawtransaction(txid))
+        output_addresses = [vout['scriptPubKey']['addresses'][0] for vout in tx["vout"]]
+        assert len(output_addresses) > 1
+        for address in output_addresses:
+            ischange = self.nodes[0].getaddressinfo(address)['ischange']
+            assert_equal(ischange, address != destination)
+            if ischange:
+                change = address
+        self.nodes[0].setlabel(change, 'foobar')
+        assert_equal(self.nodes[0].getaddressinfo(change)['ischange'], False)
 
 if __name__ == '__main__':
     WalletTest().main()