fa7bc9bbca fuzz: Fix wallet_bdb_parser 32-bit unhandled fseek error (MarcoFalke)
Pull request description:
`std::fseek` on 64-bit past the end of the file may work fine (the following read would fail). However, on 32-bit it may fail early.
Fix it, by ignoring the error, treating it similar to a read error.
This was found by OSS-Fuzz.
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=69414
ACKs for top commit:
TheCharlatan:
ACK fa7bc9bbca
brunoerg:
utACK fa7bc9bbca
Tree-SHA512: 7a752a005837bae6846ce315a7b3b1a5fe1f440c7797c750f2c0bbb20b1ef1537cd390c425747c0c85d012655e2f908bd300ea084f82e5ada19badbf826e1ec9
fa9cb101cf refactor: Add explicit cast to expected_last_page to silence fuzz ISan (MarcoFalke)
Pull request description:
Fixes#30247
I don't think this implicit cast can lead to any bugs, so make it explicit to silence the fuzz integer sanitizer.
Can be tested with:
```
FUZZ=wallet_bdb_parser UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./src/test/fuzz/fuzz /tmp/1376869be72eebcc87fe737020add634b1a29533
```
After downloading the raw fuzz input from 1376869be7
ACKs for top commit:
dergoegge:
utACK fa9cb101cf
Tree-SHA512: 226dcc58be8d70b4eec1657f232c9c6648b5dac5eb2706e7390e65ce0a031fbaf8afce97d71a535c8294467dca4757c96f294d8cc03d5e6a1c0a036b0e070325
f58beabe75 test: bumpfee with user specified fee_rate ignores walletIncrementalRelayFee (ismaelsadeeq)
436e88f433 bumpfee: ignore WALLET_INCREMENTAL_RELAY_FEE when user specifies fee rate (ismaelsadeeq)
Pull request description:
Fixes#26973
When using the `bumpfee` RPC and manually specifying `fee_rate`, there should be no requirement that the new fee must be at least the sum of the original fee and `incrementalFee` (maximum of `relayIncrementalFee` and `WALLET_INCREMENTAL_RELAY_FEE`).
This restriction should only apply when user did not specify `fee_rate`.
> because the GUI doesn't let the user specify the new fee rate yet (https://github.com/bitcoin-core/gui/issues/647), it would be very annoying to have to bump 20 times to increment by 20 sat/vbyte.
The restriction should instead be the new fee must be at least the sum of the original fee and `incrementalFee` (`relayIncrementalFee`)
ACKs for top commit:
achow101:
ACK f58beabe75
murchandamus:
ACK f58beabe75
Tree-SHA512: 193259f87173b7d5a8e68e0e29f2ca7e75c550e3cf0dee3d6d822b5b1e07c2e6dec0bfc8fb435855736ebced97a10dbdbfef72e8c5abde06fdefcba122f2e7f1
c7376babd1 doc: Clarify distinction between util and common libraries in libraries.md (Ryan Ofsky)
4f74c59334 util: Move util/string.h functions to util namespace (Ryan Ofsky)
4d05d3f3b4 util: add TransactionError includes and namespace declarations (Ryan Ofsky)
680eafdc74 util: move fees.h and error.h to common/messages.h (Ryan Ofsky)
02e62c6c9a common: Add PSBTError enum (Ryan Ofsky)
0d44c44ae3 util: move error.h TransactionError enum to node/types.h (Ryan Ofsky)
9bcce2608d util: move spanparsing.h to script/parsing.h (Ryan Ofsky)
6dd2ad4792 util: move spanparsing.h Split functions to string.h (Ryan Ofsky)
23cc8ddff4 util: move HexStr and HexDigit from util to crypto (TheCharlatan)
6861f954f8 util: move util/message to common/signmessage (Ryan Ofsky)
cc5f29fbea build: move memory_cleanse from util to crypto (Ryan Ofsky)
5b9309420c build: move chainparamsbase from util to common (Ryan Ofsky)
ffa27af24d test: Add check-deps.sh script to check for unexpected library dependencies (Ryan Ofsky)
Pull request description:
Remove `fees.h`, `errors.h`, and `spanparsing.h` from the util library. Specifically:
- Move `Split` functions from `util/spanparsing.h` to `util/string.h`, using `util` namespace for clarity.
- Move remaining spanparsing functions to `script/parsing.h` since they are used for descriptor and miniscript parsing.
- Combine `util/fees.h` and `util/errors.h` into `common/messages.h` so there is a place for simple functions that generate user messages to live, and these functions are not part of the util library.
Motivation for this change is that the util library is a dependency of the kernel, and we should remove functionality from util that shouldn't be called by kernel code or kernel applications. These changes should also improve code organization and make functions easier to discover. Some of these same moves are (or were) part of #28690, but did not help with code organization, or made it worse, so it is better to move them and clean them up in the same PR so code only has to change one time.
ACKs for top commit:
achow101:
ACK c7376babd1
TheCharlatan:
Re-ACK c7376babd1
hebasto:
re-ACK c7376babd1.
Tree-SHA512: 5bcef16c1255463b1b69270548711e7ff78ca0dd34e300b95e3ca1ce52ceb34f83d9ddb2839e83800ba36b200de30396e504bbb04fa02c6d0c24a16d06ae523d
In order to ensure that the change of nVersion to a uint32_t in the
previous commit has no effect, rename nVersion to version in this commit
so that reviewers can easily spot if a spot was missed or if there is a
check somewhere whose semantics have changed.
2451a217dd test: addmultisigaddress, coverage for script size limits (furszy)
53302a0981 bugfix: addmultisigaddress, add unsupported operation for redeem scripts over 520 bytes (furszy)
9be6065cc0 test: coverage for 16-20 segwit multisig scripts (furszy)
9d9a91c4ea rpc: bugfix, incorrect segwit redeem script size used in signrawtransactionwithkey (furszy)
0c9fedfc45 fix incorrect multisig redeem script size limit for segwit (furszy)
f7a173b578 test: rpc_createmultisig, decouple 'test_sortedmulti_descriptors_bip67' (furszy)
4f33dbd8f8 test: rpc_createmultisig, decouple 'test_mixing_uncompressed_and_compressed_keys' (furszy)
25a81705d3 test: rpc_createmultisig, remove unnecessary checkbalances() (furszy)
b5a3289433 test: refactor, multiple cleanups in rpc_createmultisig.py (furszy)
3635d43268 test: rpc_createmultisig, remove manual wallet initialization (furszy)
Pull request description:
Fixing https://github.com/bitcoin/bitcoin/issues/28250#issuecomment-1674830104 and more.
Currently, redeem scripts longer than 520 bytes, which are technically valid under segwit rules, have flaws in the following processes:
1) The multisig creation process fails to deduce the output descriptor, resulting in the generation of an incorrect descriptor. Additionally, the accompanying user warning is also inaccurate.
2) The `signrawtransactionwithkey` RPC command fail to sign them.
3) The legacy wallet `addmultisigaddress` wrongly discards them.
The issue arises because most of these flows are utilizing the legacy spkm keystore, which imposes
the [p2sh max redeem script size rule](ded6873340/src/script/signingprovider.cpp (L160)) on all scripts. Which blocks segwit redeem scripts longer than
the max element size in all the previously mentioned processes (`createmultisig`, `addmultisigaddress`, and
`signrawtransactionwithkey`).
This PR fixes the problem, enabling the creation of multisig output descriptors involving more than 15 keys and
allowing the signing of these scripts, along with other post-segwit redeem scripts that surpass the 520-byte
p2sh limit.
Important note:
Instead of adding support for these longer redeem scripts in the legacy wallet, an "unsupported operation"
error has been added. The reasons behind this decision are:
1) The introduction of this feature brings about a compatibility-breaking change that requires downgrade
protection; older wallets would be unable to interact with these "new" legacy wallets.
2) Considering the ongoing deprecation of the legacy spkm, this issue provides another compelling
reason to transition towards descriptors.
Testing notes:
To easily verify each of the fixes, I decoupled the tests into standalone commits. So they can be
cherry-picked on top of master. Where `rpc_createmultisig.py` (with and without the `--legacy-wallet`
arg) will fail without the bugs fixes commits.
Extra note:
The initial commits improves the `rpc_createmultisig.py` test in many ways. I found this test very
antiquated, screaming for an update and cleanup.
ACKs for top commit:
pinheadmz:
ACK 2451a217dd
theStack:
Code-review ACK 2451a217dd
achow101:
ACK 2451a217dd
Tree-SHA512: 71794533cbd46b3a1079fb4e9d190d3ea3b615de0cbfa443466e14f05e4616ca90e12ce2bf07113515ea8113e64a560ad572bb9ea9d4835b6fb67b6ae596167f
d7290d662f fuzz: wallet, add target for Crypter (Ayush Singh)
Pull request description:
This PR adds fuzz coverage for `wallet/crypter`.
Motivation: Issue [27272](https://github.com/bitcoin/bitcoin/issues/27272#issue-1628327906)
I ran this for a long time with Sanitizers on and had no crashes; the average `exec/sec` also looks good to me. However, I would really appreciate it if some of the reviewers could try it on their machines too, and give their feedback.
ACKs for top commit:
maflcko:
utACK d7290d662f
achow101:
ACK d7290d662f
brunoerg:
utACK d7290d662f
Tree-SHA512: f5c496cabdd3263a7e1ad49eeff702725336f76bf19a82e5dbbead082e990889dd43c851d0d2d6ab740f44b8ec2aa06defd9ff6b02be68b5f8b4eaf963f88599
fa3169b073 rpc: Remove index-based Arg accessor (MarcoFalke)
Pull request description:
The index-based Arg accessor is redundant with the name-based one. It does not provide any benefit to the code reader, or otherwise, so remove it.
ACKs for top commit:
stickies-v:
re-ACK fa3169b073, addressed doc nits
achow101:
ACK fa3169b073
ryanofsky:
Code review ACK fa3169b073. One changes since last review are some documentation improvements
Tree-SHA512: f9da1c049dbf38c3b47a8caf8d24d195c2d4b88c7ec45a9ccfb78f1e39f29cb86869f84b308f6e49856b074c06604ab634c90eb89c9c93d2a8169e070aa1bd40
71aae72e1f test: test sendall does ancestor aware funding (ishaanam)
36757941a0 wallet, rpc: implement ancestor aware funding for sendall (ishaanam)
544131f3fb rpc, test: test sendall spends unconfirmed change and unconfirmed inputs when specified (ishaanam)
Pull request description:
This PR:
- Adds a functional test that `sendall` spends unconfirmed change
- Adds a functional test that `sendall` spends regular unconfirmed inputs when specified by user
- Adds ancestor aware funding to `sendall` by using `calculateCombinedBumpFee` and adjusting the effective value accordingly
- Adds a functional test for ancestor aware funding in `sendall`
ACKs for top commit:
S3RK:
ACK 71aae72e1f
achow101:
ACK 71aae72e1f
furszy:
ACK 71aae72e1f
Tree-SHA512: acaeb7c65166ce53123a1d6cb5012197202246acc02ef9f37a28154cc93afdbd77c25e840ab79bdc7e0b88904014a43ab1ddea79d5337dc310ea210634ab61f0
bd34dd85e7 Use `exact_target` shorthand in coinselector_tests (Murch)
7aa7e30441 Fold GetSelectionWaste() into ComputeAndSetWaste() (Murch)
Pull request description:
PR #26152 moved waste calculation into SelectionResult to be able to correct the waste score on basis of the bump_fee_group_discount for overlapping ancestries. This left two functions with largely overlapping purpose, where one was simply a wrapper of the other. This PR cleans up the overlap, and fixes the double-meaning of `change_cost` where the `GetChange()` function assumed that no change was created when `change_cost` was set to 0. This behavior was exploited in a bunch of tests, but is problematic, because a `change_cost` of 0 is permitted with custom settings for feerate and discard_feerate (i.e. when they’re both 0).
ACKs for top commit:
achow101:
ACK bd34dd85e7
furszy:
Code ACK bd34dd85e7
ismaelsadeeq:
Code Review ACK bd34dd85e7
Tree-SHA512: 83a2688d45d719dc61a64b5180fe136107faccf401a59df65245c05d701748a03e85ed56fde8c9b7ef39a3ab54374dd3718c559bda5b3f55dafedfd7fed25161
e3249f2111 fuzz: add more coverage for `ScriptPubKeyMan` (brunoerg)
Pull request description:
This PR adds more coverage for `ScriptPubKeyMan`:
- Check `GetKey` and `HasPrivKey` after adding descriptor key.
- Cover `GetEndRange` and `GetKeyPoolSize`.
- Cover `MarkUnusedAddresses` with the scripts from ScriptPubKeys and `GetMetadata` with the destinations from them.
ACKs for top commit:
marcofleon:
Tested ACK e3249f2111. I ran the updated harness for ~9 hours on an empty corpus, generated a coverage report, and checked that the new functions mentioned were hit. Coverage of `scriptpubkeyman.cpp` increased.
murchandamus:
Tested ACK e3249f2111
Tree-SHA512: cfab91f6c8401174842e79209c0e9225c08f011fe9b41d0a58bcec716ae4545eaf803867f899ed7b5fbcefea45711f91894e36df082ba19732dd310cd9e61a79
Both `GetSelectionWaste()` and `ComputeAndSetWaste()` now are part of
`SelectionResult`. Instead of `ComputeAndSetWaste()` being a wrapper for
`GetSelectionWaste()`, we combine them to a new function
`RecalculateWaste()`.
As I was combining the logic of the two functions, I noticed that
`GetSelectionWaste()` was making the odd assumption that the
`change_cost` being set to zero means that no change is created.
However, if we build transactions at a feerate of zero with the
`discard_feerate` also set to zero, we'd organically have a
`change_cost` of zero, even when we create change on a transaction.
This commit cleans up this duplicate meaning of `change_cost` and relies
on `GetChange()` to figure out whether there is change on basis of the
`min_viable_change` and whatever is left after deducting fees.
Since this broke a bunch of tests that relied on the double-meaning of
`change_cost` a bunch of tests had to be fixed.
d7707d9843 rpc: avoid copying into UniValue (Cory Fields)
Pull request description:
These are the simple (and hopefully obviously correct) copies that can be moves instead.
This is a follow-up from https://github.com/bitcoin/bitcoin/pull/30094#issuecomment-2108751842
As it turns out, there are hundreds of places where we copy UniValues needlessly. It should be the case that moves are always preferred over copies, so there should be no downside to these changes.
willcl-ark, however, noticed that memory usage may increase in some cases. Logically this makes no sense to me. The only plausible explanation imo is that because the moves are faster, more ops/second occur in some cases.
This list of moves was obtained by changing the function signatures of the UniValue functions to accept only rvalues, then compiling and fixing them up one by one. There still exist many places where copies are being made. These can/should be fixed up, but weren't done here for the sake of doing the easy ones first.
I ran these changes through clang-tidy with `performance-move-const-arg` and `bugprone-use-after-move` and no bugs were detected (though that's obviously not to say it can be trusted 100%).
As stated above, there are still lots of other less trivial fixups to do after these including:
- Using non-const UniValues where possible so that moves can happen
- Refactoring code in order to be able to move a UniValue without introducing a use-after-move
- Refactoring functions to accept UniValues by value rather than by const reference
ACKs for top commit:
achow101:
ACK d7707d9843
ryanofsky:
Code review ACK d7707d9843. No changes since last review other than rebase. I agree benchmarks showing increased peak memory usage and RSS are surprising, but number of allocations is down as expected, and runtime is also decreased.
willcl-ark:
ACK d7707d9843
Tree-SHA512: 7f511be73984553c278186286a7d161a34b2574c7f5f1a0edc87c2913b4c025a0af5241ef9af2df17547f2e4ef79710aa5bbb762fc9472435781c0488dba3435
d51fbab4b3 wallet, test: Be able to always swap BDB endianness (Ava Chow)
0b753156ce test: Test bdb_ro dump of wallet without reset LSNs (Ava Chow)
c1984f1282 test: Test dumping dbs with overflow pages (Ava Chow)
fd7b16e391 test: Test dumps of other endian BDB files (Ava Chow)
6ace3e953f bdb: Be able to make byteswapped databases (Ava Chow)
d9878903fb Error if LSNs are not reset (Ava Chow)
4d7a3ae78e Berkeley RO Database fuzz test (TheCharlatan)
3568dce9e9 tests: Add BerkeleyRO to db prefix tests (Ava Chow)
70cfbfdadf wallettool: Optionally use BERKELEY_RO as format when dumping BDB wallets (Ava Chow)
dd57713f6e Add MakeBerkeleyRODatabase (Ava Chow)
6e50bee67d Implement handling of other endianness in BerkeleyRODatabase (Ava Chow)
cdd61c9cc1 wallet: implement independent BDB deserializer in BerkeleyRODatabase (Ava Chow)
ecba230979 wallet: implement BerkeleyRODatabase::Backup (Ava Chow)
0c8e728476 wallet: implement BerkeleyROBatch (Ava Chow)
756ff9b478 wallet: add dummy BerkeleyRODatabase and BerkeleyROBatch classes (Ava Chow)
ca18aea5c4 Add AutoFile::seek and tell (Ava Chow)
Pull request description:
Split from #26596
This PR adds `BerkeleyRODatabase` which is an independent implementation of a BDB file parser. It provides read only access to a BDB file, and can therefore be used as a read only database backend for wallets. This will be used for dumping legacy wallet records and migrating legacy wallets without the need for BDB itself.
Wallettool's `dump` command is changed to use `BerkeleyRODatabase` instead of `BerkeleyDatabase` (and `CWallet` itself) to demonstrate that this parser works and to test it against the existing wallettool functional tests.
ACKs for top commit:
josibake:
reACK d51fbab4b3
TheCharlatan:
Re-ACK d51fbab4b3
furszy:
reACK d51fbab4b3
laanwj:
re-ACK d51fbab4b3
theStack:
ACK d51fbab4b3
Tree-SHA512: 1e7b97edf223b2974eed2e9eac1179fc82bb6359e0a66b7d2a0c8b9fa515eae9ea036f1edf7c76cdab2e75ad994962b134b41056ccfbc33b8d54f0859e86657b
BerkeleyRODatabase is intended for use after BDB is removed, so it needs
to be able to read all of the records from a BDB file. Thus an
independent deserializer for BDB data files is implemented in it. This
deserializer is targeted towards the data files that Bitcoin Core
creates so it does not fully support all of BDB's features (e.g. other
database types, encryption, etc.).
There are no changes to behavior. Changes in this commit are all additions, and
are easiest to review using "git diff -U0 --word-diff-regex=." options.
Motivation for this change is to keep util functions with really generic names
like "Split" and "Join" out of the global namespace so it is easier to see
where these functions are defined, and so they don't interfere with function
overloading, especially since the util library is a dependency of the kernel
library and intended to be used with external code.
Add TransactionError to node namespace and include it directly instead of
relying on indirect include through common/messages.h
This is a followup to a previous commit which moved the TransactionError enum.
These changes were done in a separate followup just to keep the previous commit
more minimal and easy to review.
Move enum and message formatting functions to a common/messages header where
they should be more discoverable, and also out of the util library, so they
will not be a dependency of the kernel
The are no changes in behavior and no changes to the moved code.
Add separate PSBTError enum instead of reusing TransactionError enum for PSBT
operations, and drop unused error codes. The error codes returned by PSBT
operations and transaction broadcast functions mostly do not overlap, so using
an unified enum makes it harder to call any of these functions and know which
errors actually need to be handled.
Define PSBTError in the common library because PSBT functionality is
implemented in the common library and used by both the node (for rawtransaction
RPCs) and the wallet.
New node/types.h file is analagous to existing wallet/types.h and is a better
place to define simple node types that are shared externally with wallet and
gui code than the util library.
Motivation for this change is to completely remove util/error.h file currently
holding TransactionError in a followup commit.
Move util/message to common/signmessage so it is named more clearly, and
because the util library is not supposed to depend on other libraries besides
the crypto library. The signmessage functions use CKey, CPubKey, PKHash, and
DecodeDestination functions in the consensus and common libraries.
Implement ReadKey and HasKey of BerkeleyROBatch, and Next of BerkeleyROCursor.
Also adds the containers for records to BerkeleyRODatabase so that
BerkeleyROBatch will be able to access the records.
98570fe29b test: add coverage for parsing cryptographically invalid pubkeys (Sebastian Falbesoner)
c740b154d1 rpc: use `HexToPubKey` helper for all legacy pubkey-parsing RPCs (Sebastian Falbesoner)
100e8a75bf rpc: check and throw specific pubkey parsing errors in `HexToPubKey` (Sebastian Falbesoner)
Pull request description:
Parsing legacy public keys can fail for three reasons (in this order):
- pubkey is not in hex
- pubkey has an invalid length (not 33 or 65 bytes for compressed/uncompressed, respectively)
- pubkey is crytographically invalid, i.e. is not on curve (`CPubKey.IsFullyValid()` check)
Many RPCs currently perform these checks manually with different error messages, even though we already have a `HexToPubKey` helper. This PR puts all three checks in this helper (the length check was done on the call-sites before), adds specific error messages for each case, and consequently uses it for all RPCs that parse legacy pubkeys. This leads to deduplicated code and also to more consistent and detailed error messages for the user.
Affected RPC calls are `createmultisig`, `addmultisigaddress`, `importpubkey`, `importmulti`, `fundrawtransaction`, `walletcreatefundedpsbt`, `send` and `sendall`.
Note that the error code (-5 a.k.a. `RPC_INVALID_ADDRESS_OR_KEY`) doesn't change in any of the causes, so the changes are not breaking RPC API compatibility. Only the messages are more specific.
The last commits adds test coverage for the cryptographically invalid (not-on-curve) pubkey case which wasn't exercised before.
ACKs for top commit:
stratospher:
tested ACK 98570fe.
davidgumberg:
ACK 98570fe29b
Eunovo:
Tested ACK 98570fe29b
achow101:
ACK 98570fe29b
Tree-SHA512: cfa474176e95b5b18f3a9da28fdd9e87195cd58994c1331198f2840925fff322fd323a6371feab74a1b32e4b9ea58a6dc732fa751b4cdd45402c1029af609ece
Due to a bug in the legacy wallet, the p2sh maximum script size limit is also imposed
on 'p2sh-segwit' and 'bech32' redeem scripts.
Although redeem scripts over MAX_SCRIPT_ELEMENT_SIZE bytes are technically valid for
segwit output types, we don't want to enable this feature in legacy wallets for the
following reasons:
1) It introduces a compatibility-breaking change requiring downgrade protection; older
wallets would be unable to interact with these "new" legacy wallets.
2) Considering the ongoing deprecation of the legacy spkm, this issue adds another
good reason to transition towards descriptors.
The multisig script generation process currently fails when
the user exceeds 15 keys, even when it shouldn't. The maximum
number of keys allowed for segwit redeem scripts (p2sh-segwit
and bech32) is 20 keys.
This is because the redeem script placed in the witness is not
restricted by the item size limit.
The reason behind this issue is the utilization of the legacy
p2sh redeem script restrictions on segwit ones. Redeem scripts
longer than 520 bytes are blocked from being inserted into the
keystore, which causes the signing process and the descriptor
inference process to fail.
This occurs because the multisig generation flow uses the same
keystore as the legacy spkm (FillableSigningProvider), which
contains the 520-byte limit.
6a8b2befea refactor: Avoid copying util::Result values (Ryan Ofsky)
834f65e824 refactor: Drop util::Result operator= (Ryan Ofsky)
Pull request description:
This PR just contains the first two commits of #25665.
It disables copying of `util::Result` objects because unnecessary copies are inefficient and not possible after #25665, which makes `util::Result` object move-only.
It disables the assignment operator and replaces it with an `Update()` method, because #25665 adds more information to `util::Result` objects (warning and error messages and failure values) and having an assignment operator that overwrites data instead of merging it would make it easy to accidentally erase existing information while trying to assign new information.
ACKs for top commit:
stickies-v:
re-ACK 6a8b2befea
achow101:
ACK 6a8b2befea
furszy:
re-ACK 6a8b2befea
Tree-SHA512: 3f21af9031d50d6c68cca69133de03080f69b1ddcf8b140bdeb762069f14645209b2586037236d15b6ebd8973af0fbefd7e83144aeb7b84078a4cb4df812f984
30a6c99935 rpc: access some args by name (stickies-v)
bbb31269bf rpc: add named arg helper (stickies-v)
13525e0c24 rpc: add arg helper unit test (stickies-v)
Pull request description:
Adds string overloads for the `RPCHelpMan::Arg` and `RPCHelpMan::MaybeArg` helpers to be able to access RPC arguments by name instead of index number. Especially in RPCs with a large number of parameters, this can be quite helpful.
Example usage:
```cpp
const auto action{self.Arg<std::string>("action")};
```
Most of the LoC is adding test coverage and documentation updates. No behaviour change.
An alternative approach to #27788 with significantly less overhaul.
ACKs for top commit:
fjahr:
Code review ACK 30a6c99935
maflcko:
ACK 30a6c99935🥑
ryanofsky:
Code review ACK 30a6c99935. Nice change! Implementation is surprisingly simple and additional unit test coverage is welcome, too.
Tree-SHA512: 4904f5f914fe1d421d32f60edb7c5a028c8ea0f140a2f207a106b4752d441164e073066a6bf2e17693f859fe847815a96609d3cf521e0ac4178d8cd09362ea3d
