rpc: add "ischange: true" to decoded tx outputs in wallet gettransaction response

pinheadmz commented at 3:40 pm on May 15, 2025: member

This change is motivated by external RBF clients like https://github.com/CardCoins/additive-rbf-batcher/. It saves the user a redundant re-looping of tx outputs, calling getaddressinfo on each one, looking for the change output in order to adjust the fee.

The field "ischange" only appears when gettransaction is called on a wallet, and is either true or not present at all. I chose not to include ischange: false because it is confusing to see that on received transactions.

Example of the new field:

 0    "vout": [
 1      {
 2        "value": 1.00000000,
 3        "n": 0,
 4        "scriptPubKey": {
 5          "asm": "0 5483235e05c76273b3b50af62519738781aff021",
 6          "desc": "addr(bcrt1q2jpjxhs9ca388va4ptmz2xtns7q6lupppkw7wu)#d42g84j6",
 7          "hex": "00145483235e05c76273b3b50af62519738781aff021",
 8          "address": "bcrt1q2jpjxhs9ca388va4ptmz2xtns7q6lupppkw7wu",
 9          "type": "witness_v0_keyhash"
10        }
11      },
12      {
13        "value": 198.99859000,
14        "n": 1,
15        "scriptPubKey": {
16          "asm": "0 870ab1ab58632b05a417d5295f4038500e407592",
17          "desc": "addr(bcrt1qsu9tr26cvv4stfqh65547spc2q8yqavj7fnlju)#tgapemkv",
18          "hex": "0014870ab1ab58632b05a417d5295f4038500e407592",
19          "address": "bcrt1qsu9tr26cvv4stfqh65547spc2q8yqavj7fnlju",
20          "type": "witness_v0_keyhash"
21        },
22        "ischange": true
23      }
24    ]

rpc: add "ischange: true" in wallet gettransaction decoded tx output bef143cc28

DrahtBot commented at 3:40 pm on May 15, 2025: contributor

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32517.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

#31252 (rpc: print P2WSH and P2SH redem Script in getrawtransaction by polespinasa)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

DrahtBot added the label RPC/REST/ZMQ on May 15, 2025

in src/rpc/rawtransaction.cpp:121 in bef143cc28 outdated

117@@ -118,6 +118,7 @@ static std::vector<RPCResult> DecodeTxDoc(const std::string& txid_field_doc)
118                 {RPCResult::Type::STR_AMOUNT, "value", "The value in " + CURRENCY_UNIT},
119                 {RPCResult::Type::NUM, "n", "index"},
120                 {RPCResult::Type::OBJ, "scriptPubKey", "", ScriptPubKeyDoc()},
121+                {RPCResult::Type::BOOL, "ischange", /*optional=*/true, "Output script is change (only if wallet transaction and true for selected rpcwallet)"},

maflcko commented at 4:12 pm on May 15, 2025:

nit: Not sure about making this optional out of convenience and then write the rule in the description string.

It would be better to just pass down a std::optionl<RPCResult> (or std::vector<RPCResult>) here, and then use Cat() to concatenate it?

pinheadmz commented at 4:39 pm on May 15, 2025:

Not sure what you mean here – help gettransaction doesn’t list this at all, it just tells the user to check decoderawtransaction

maflcko commented at 5:04 pm on May 15, 2025:

Hmm, looks like you are right. Though, that doesn’t seem very machine readable. It is a bit unrelated, but I can try to fix it, if you don’t want to include it here.

pinheadmz commented at 5:43 pm on May 15, 2025:

Ill give it a shot in this branch

pinheadmz commented at 2:16 pm on May 16, 2025:

done

[move only] move DecodeTxDoc() to a common util file for sharing 23d779dcf5

rpc: add decoded tx details to gettransaction with extra wallet fields f6517df210

rpc: add “ischange: true” to decoded tx outputs in wallet gettransaction response #32517

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