Neard doesn't warn about unrecognised options in config.json

[jancionear]

Describe the bug

When neard reads config.json, it should validate that all options in the config are correct. It shouldn't ignore options that are unrecognised, because then there's a risk that the operator will make a typo in the config and they will unknowingly run a misconfigured node.

There was another issue about it (#6436), and it looks like the feature has been implemented in #6490 (which should've closed #6436), but it doesn't work.
This issue is about a bug in the implementation of #6436. The logic is there, but it doesn't produce any warnings: https://github.com/near/nearcore/blob/abf6e99bad479a216a7f6e8a465a3eaf0523659e/nearcore/src/config.rs#L496C17-L496C27

To Reproduce

1. In ~/.near/config.json add a parameter that doesn't exist. For example:

{
  "anotheroptionthatdoesntexist": "whatisthat",
  "genesis_file": "genesis.json",
  "genesis_records_file": null,

2. Run neard:

cargo run --bin neard -- run

3. There's no warning about the nonexistent option:

2023-12-07T10:29:10.084808Z  INFO config: Validating Config, extracted from config.json...
2023-12-07T10:29:10.084964Z  INFO near_o11y::reload: Updated the logging layer according to `log_config.json`
2023-12-07T10:29:10.085140Z  INFO db_opener: Opening NodeStorage path="/Users/jancio/.near/data" cold_path="none"
2023-12-07T10:29:10.085290Z  INFO db: Opened a new RocksDB instance. num_instances=1
2023-12-07T10:29:10.090302Z  INFO db: Closed a RocksDB instance. num_instances=0
2023-12-07T10:29:10.090315Z  INFO db_opener: The database exists. path=/Users/jancio/.near/data
2023-12-07T10:29:10.090334Z  INFO db: Opened a new RocksDB instance. num_instances=1
2023-12-07T10:29:10.126215Z  INFO db: Closed a RocksDB instance. num_instances=0
2023-12-07T10:29:10.126256Z  INFO db: Opened a new RocksDB instance. num_instances=1
2023-12-07T10:29:10.127329Z  INFO db: Closed a RocksDB instance. num_instances=0
2023-12-07T10:29:10.127351Z  INFO db: Opened a new RocksDB instance. num_instances=1
...

Expected behavior
I expected to see a warning that there's an unrecognised option in config.json.

Version (please complete the following information):

• nearcore commit/branch: 8985a96 (master)
• rust version (if local): cargo 1.74.0 (ecb9851af 2023-10-18)
• docker (if using docker): no
• mainnet/testnet/betanet/local: local

[jancionear]

I added a bit of debug information (the code is on this branch: https://github.com/jancionear/nearcore/tree/config-debug).
Output:

2023-12-07T10:31:58.340878Z  INFO neard: version="trunk" build="1.1.0-4648-g5b5634bf7-modified" latest_protocol=64
Reading config from file: "/Users/jancio/.near/config.json"
Config starts with: {
  "anotheroptionthatdoesntexist": "whatisthat",
  "genesis_file": "genesis.json",
  "genesis_records_file": null,
  "validator_key_file": "validator_key.json",
  "node_key_file": "node_key.json",
  
[nearcore/src/config.rs:510] unrecognised_fields.len() = 0
2023-12-07T10:31:58.345258Z  INFO config: Validating Config, extracted from config.json...
2023-12-07T10:31:58.347211Z  WARN genesis: Skipped genesis validation
2023-12-07T10:31:58.347301Z  INFO config: Validating Genesis config and records. This could take a few minutes...
2023-12-07T10:31:58.347713Z  INFO config: All validations have passed!
2023-12-07T10:31:58.352408Z  INFO neard: Reset the config "/Users/jancio/.near/log_config.json" because the config file doesn't exist. err=Os { code: 2, kind: NotFound, message: "No such file or directory" }
Reading config from file: "/Users/jancio/.near/config.json"
Config starts with: {
  "anotheroptionthatdoesntexist": "whatisthat",
  "genesis_file": "genesis.json",
  "genesis_records_file": null,
  "validator_key_file": "validator_key.json",
  "node_key_file": "node_key.json",
  
[nearcore/src/config.rs:510] unrecognised_fields.len() = 0
2023-12-07T10:31:58.352763Z  INFO config: Validating Config, extracted from config.json...
2023-12-07T10:31:58.352974Z  INFO near_o11y::reload: Updated the logging layer according to `log_config.json`
2023-12-07T10:31:58.353240Z  INFO db_opener: Opening NodeStorage path="/Users/jancio/.near/data" cold_path="none"
2023-12-07T10:31:58.353433Z  INFO db: Opened a new RocksDB instance. num_instances=1
2023-12-07T10:31:58.360813Z  INFO db: Closed a RocksDB instance. num_instances=0

It looks like the unrecognised_fields variable is always empty, despite having an invalid option in the config. This makes me suspicious of serde_ignored::deserialize, maybe it's doing a different thing from what the authors expected it to do?
(code for reference: https://github.com/near/nearcore/blob/abf6e99bad479a216a7f6e8a465a3eaf0523659e/nearcore/src/config.rs#L496C17-L496C27)

[nagisa]

Duplicate of #9073. Since you're looking into this, up to you which issue you want to keep.

[jancionear]

Duplicate of #9073. Since you're looking into this, up to you which issue you want to keep.

Thanks, I didn't see it. I searched for unrecongised, but not for unrecognized x.x
It's a shame that github's search isn't more fuzzy.

#9073 seems like a better issue, it actually explains why things are wrong and links to the serde_ignore bug. I will close this one.

[jancionear]

Closing as a duplicate of #9073