astral-sh/ruff · error

RuleSelector::specificity doesn't yet support codes with so

Error message

RuleSelector::specificity doesn't yet support codes with so many characters

What it means

Panics inside RuleSelector::specificity because a Prefix selector's code is longer than any length the match on prefix.len() covers. The specificity ladder is only implemented for prefixes up to a fixed character count, so an over-long rule prefix reaches an unhandled arm.

Source

Thrown at crates/ruff_linter/src/rule_selector.rs:462

}

impl RuleSelector {
    pub fn specificity(&self) -> Specificity {
        match self {
            RuleSelector::All => Specificity::All,
            RuleSelector::Category(..) => Specificity::Category,
            RuleSelector::T => Specificity::LinterGroup,
            RuleSelector::C => Specificity::LinterGroup,
            RuleSelector::Linter(..) => Specificity::Linter,
            RuleSelector::Rule { .. } => Specificity::Rule,
            RuleSelector::Prefix { prefix, .. } => {
                let prefix: &'static str = prefix.short_code();
                match prefix.len() {
                    1 => Specificity::Prefix1Char,
                    2 => Specificity::Prefix2Chars,
                    3 => Specificity::Prefix3Chars,
                    4 => Specificity::Prefix4Chars,
                    _ => panic!(
                        "RuleSelector::specificity doesn't yet support codes with so many characters"
                    ),
                }
            }
        }
    }

    /// Parse [`RuleSelector`] from a string; but do not follow redirects.
    #[cfg(feature = "schemars")]
    fn parse_no_redirect(s: &str) -> Result<Self, ParseError> {
        // **Changes should be reflected in `from_str` as well**
        match s {
            "ALL" => Ok(Self::All),
            "C" => Ok(Self::C),
            "T" => Ok(Self::T),
            _ => {
                let (linter, code) =
                    Linter::parse_code(s).ok_or_else(|| ParseError::Unknown(s.to_string()))?;

View on GitHub (pinned to 26f38c119c)

Solutions

1. Extend the length match arms in specificity to cover longer prefixes
2. Use a shorter, well-formed rule prefix in the selector

When it happens

Trigger: Thrown at crates/ruff_linter/src/rule_selector.rs:462 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of astral-sh/ruff@26f38c119c (2026-09-05). Data as JSON: /api/errors/f25ecfd63c6e1661. Report an issue: GitHub.