What happens currently

At the moment, ignoring a rule code that Ruff doesn't know about in the ignore setting will cause an error:
For example using ruff==0.5.6:

[lint]
select = ["ALL"]
ignore = [
  # ...
  "DOC201", # docstring-missing-returns
  "DOC402", # docstring-missing-yields
  "DOC501", # docstring-missing-exception
]

Results in:

ruff failed
  Cause: Failed to parse [...]]\ruff.toml
  Cause: TOML parse error at line 17, column 1
   |
17 | [lint]
   | ^^^^^^
Unknown rule selector: `DOC402`

What I'd like to see

I'd like such errors, for ignore specifically, to be warnings instead

Why ?

For shared configurations. Not completely failing on unknown ignored error codes allows the same configuration to be valid for a wider range of Ruff versions, reducing maintenance and increasing compatibility on the configuration side. Whether it's because the consumer has updated to a new Ruff version that removed that rule, or because they're still behind but the config disabled a rule they don't have access to yet.

Whilst rn shared configs are mostly done through copy-and-paste (https://github.com/BesLogic/shared-configs/blob/main/ruff.toml) or some sort of git management (https://github.com/jaraco/skeleton/blob/main/ruff.toml). This will become especially relevant with #12352

Why only ignore ?

This request opens the question: why not do the same for rule selection or settings? Because those convey an explicit desire for the code to conform to those rules and configurations. Ignoring a rule, whether it exists or not, results in the same lint validation.

Prior art

ESLint works very similarly to what I'm asking, with the only difference that it completely ignores the disabled rule, instead of warning.
The "enable all rules + disable what we don't want or need" pattern has allowed me with https://www.npmjs.com/package/eslint-config-beslogic to support a wide range of peer dependencies whilst staying mostly up to date with new rules (until I need to reconfigure a non-disabled newly added rule, but with ESLint's JS-based configs I have ways to work around that too with version-detection, although that's not relevant here)

Flake8 only errors-out on rule codes that are completely impossible. For example ignoring AAAA results in ValueError: Error code 'AAAA' supplied to 'extend-ignore' option does not match '^[A-Z]{1,3}[0-9]{0,3}$'

Ruff is already able to output warnings, for example when linting non-UTF-8 files:

warning: Failed to lint Pythonwin\pywin\test\_dbgscript.py: stream did not contain valid UTF-8