diff --git a/regex-automata/src/dfa/dense.rs b/regex-automata/src/dfa/dense.rs index ed37d3b84..fdae99fa6 100644 --- a/regex-automata/src/dfa/dense.rs +++ b/regex-automata/src/dfa/dense.rs @@ -4958,6 +4958,74 @@ pub struct BuildError { kind: BuildErrorKind, } +#[cfg(feature = "dfa-build")] +impl BuildError { + /// Returns true if and only if this error corresponds to an error with DFA + /// construction that occurred because of exceeding a size limit. + /// + /// While this can occur when size limits like [`Config::dfa_size_limit`] + /// or [`Config::determinize_size_limit`] are exceeded, this can also occur + /// when the number of states or patterns exceeds a hard-coded maximum. + /// (Where these maximums are derived based on the values representable by + /// [`StateID`] and [`PatternID`].) + /// + /// This predicate is useful in contexts where you want to distinguish + /// between errors related to something provided by an end user (for + /// example, an invalid regex pattern) and errors related to configured + /// heuristics. For example, building a DFA might be an optimization that + /// you want to skip if construction fails because of an exceeded size + /// limit, but where you want to bubble up an error if it fails for some + /// other reason. + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// # if !cfg!(target_pointer_width = "64") { return Ok(()); } // see #1039 + /// use regex_automata::{dfa::{dense, Automaton}, Input}; + /// + /// let err = dense::Builder::new() + /// .configure(dense::Config::new() + /// .determinize_size_limit(Some(100_000)) + /// ) + /// .build(r"\w{20}") + /// .unwrap_err(); + /// // This error occurs because a size limit was exceeded. + /// // But things are otherwise valid. + /// assert!(err.is_size_limit_exceeded()); + /// + /// let err = dense::Builder::new() + /// .build(r"\bxyz\b") + /// .unwrap_err(); + /// // This error occurs because a Unicode word boundary + /// // was used without enabling heuristic support for it. + /// // So... not related to size limits. + /// assert!(!err.is_size_limit_exceeded()); + /// + /// let err = dense::Builder::new() + /// .build(r"(xyz") + /// .unwrap_err(); + /// // This error occurs because the pattern is invalid. + /// // So... not related to size limits. + /// assert!(!err.is_size_limit_exceeded()); + /// + /// # Ok::<(), Box>(()) + /// ``` + #[inline] + pub fn is_size_limit_exceeded(&self) -> bool { + use self::BuildErrorKind::*; + + match self.kind { + NFA(_) | Unsupported(_) => false, + TooManyStates + | TooManyStartStates + | TooManyMatchPatternIDs + | DFAExceededSizeLimit { .. } + | DeterminizeExceededSizeLimit { .. } => true, + } + } +} + /// The kind of error that occurred during the construction of a DFA. /// /// Note that this error is non-exhaustive. Adding new variants is not