diff options
Diffstat (limited to 'third_party/rust/regex-automata/src/meta/error.rs')
-rw-r--r-- | third_party/rust/regex-automata/src/meta/error.rs | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/third_party/rust/regex-automata/src/meta/error.rs b/third_party/rust/regex-automata/src/meta/error.rs new file mode 100644 index 0000000000..ea9a3160e0 --- /dev/null +++ b/third_party/rust/regex-automata/src/meta/error.rs @@ -0,0 +1,241 @@ +use regex_syntax::{ast, hir}; + +use crate::{nfa, util::search::MatchError, PatternID}; + +/// An error that occurs when construction of a `Regex` fails. +/// +/// A build error is generally a result of one of two possible failure +/// modes. First is a parse or syntax error in the concrete syntax of a +/// pattern. Second is that the construction of the underlying regex matcher +/// fails, usually because it gets too big with respect to limits like +/// [`Config::nfa_size_limit`](crate::meta::Config::nfa_size_limit). +/// +/// This error provides very little introspection capabilities. You can: +/// +/// * Ask for the [`PatternID`] of the pattern that caused an error, if one +/// is available. This is available for things like syntax errors, but not for +/// cases where build limits are exceeded. +/// * Ask for the underlying syntax error, but only if the error is a syntax +/// error. +/// * Ask for a human readable message corresponding to the underlying error. +/// * The `BuildError::source` method (from the `std::error::Error` +/// trait implementation) may be used to query for an underlying error if one +/// exists. There are no API guarantees about which error is returned. +/// +/// When the `std` feature is enabled, this implements `std::error::Error`. +#[derive(Clone, Debug)] +pub struct BuildError { + kind: BuildErrorKind, +} + +#[derive(Clone, Debug)] +enum BuildErrorKind { + Syntax { pid: PatternID, err: regex_syntax::Error }, + NFA(nfa::thompson::BuildError), +} + +impl BuildError { + /// If it is known which pattern ID caused this build error to occur, then + /// this method returns it. + /// + /// Some errors are not associated with a particular pattern. However, any + /// errors that occur as part of parsing a pattern are guaranteed to be + /// associated with a pattern ID. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, PatternID}; + /// + /// let err = Regex::new_many(&["a", "b", r"\p{Foo}", "c"]).unwrap_err(); + /// assert_eq!(Some(PatternID::must(2)), err.pattern()); + /// ``` + pub fn pattern(&self) -> Option<PatternID> { + match self.kind { + BuildErrorKind::Syntax { pid, .. } => Some(pid), + _ => None, + } + } + + /// If this error occurred because the regex exceeded the configured size + /// limit before being built, then this returns the configured size limit. + /// + /// The limit returned is what was configured, and corresponds to the + /// maximum amount of heap usage in bytes. + pub fn size_limit(&self) -> Option<usize> { + match self.kind { + BuildErrorKind::NFA(ref err) => err.size_limit(), + _ => None, + } + } + + /// If this error corresponds to a syntax error, then a reference to it is + /// returned by this method. + pub fn syntax_error(&self) -> Option<®ex_syntax::Error> { + match self.kind { + BuildErrorKind::Syntax { ref err, .. } => Some(err), + _ => None, + } + } + + pub(crate) fn ast(pid: PatternID, err: ast::Error) -> BuildError { + let err = regex_syntax::Error::from(err); + BuildError { kind: BuildErrorKind::Syntax { pid, err } } + } + + pub(crate) fn hir(pid: PatternID, err: hir::Error) -> BuildError { + let err = regex_syntax::Error::from(err); + BuildError { kind: BuildErrorKind::Syntax { pid, err } } + } + + pub(crate) fn nfa(err: nfa::thompson::BuildError) -> BuildError { + BuildError { kind: BuildErrorKind::NFA(err) } + } +} + +#[cfg(feature = "std")] +impl std::error::Error for BuildError { + fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { + match self.kind { + BuildErrorKind::Syntax { ref err, .. } => Some(err), + BuildErrorKind::NFA(ref err) => Some(err), + } + } +} + +impl core::fmt::Display for BuildError { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + match self.kind { + BuildErrorKind::Syntax { pid, .. } => { + write!(f, "error parsing pattern {}", pid.as_usize()) + } + BuildErrorKind::NFA(_) => write!(f, "error building NFA"), + } + } +} + +/// An error that occurs when a search should be retried. +/// +/// This retry error distinguishes between two different failure modes. +/// +/// The first is one where potential quadratic behavior has been detected. +/// In this case, whatever optimization that led to this behavior should be +/// stopped, and the next best strategy should be used. +/// +/// The second indicates that the underlying regex engine has failed for some +/// reason. This usually occurs because either a lazy DFA's cache has become +/// ineffective or because a non-ASCII byte has been seen *and* a Unicode word +/// boundary was used in one of the patterns. In this failure case, a different +/// regex engine that won't fail in these ways (PikeVM, backtracker or the +/// one-pass DFA) should be used. +/// +/// This is an internal error only and should never bleed into the public +/// API. +#[derive(Debug)] +pub(crate) enum RetryError { + Quadratic(RetryQuadraticError), + Fail(RetryFailError), +} + +#[cfg(feature = "std")] +impl std::error::Error for RetryError {} + +impl core::fmt::Display for RetryError { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + match *self { + RetryError::Quadratic(ref err) => err.fmt(f), + RetryError::Fail(ref err) => err.fmt(f), + } + } +} + +impl From<MatchError> for RetryError { + fn from(merr: MatchError) -> RetryError { + RetryError::Fail(RetryFailError::from(merr)) + } +} + +/// An error that occurs when potential quadratic behavior has been detected +/// when applying either the "reverse suffix" or "reverse inner" optimizations. +/// +/// When this error occurs, callers should abandon the "reverse" optimization +/// and use a normal forward search. +#[derive(Debug)] +pub(crate) struct RetryQuadraticError(()); + +impl RetryQuadraticError { + pub(crate) fn new() -> RetryQuadraticError { + RetryQuadraticError(()) + } +} + +#[cfg(feature = "std")] +impl std::error::Error for RetryQuadraticError {} + +impl core::fmt::Display for RetryQuadraticError { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + write!(f, "regex engine gave up to avoid quadratic behavior") + } +} + +impl From<RetryQuadraticError> for RetryError { + fn from(err: RetryQuadraticError) -> RetryError { + RetryError::Quadratic(err) + } +} + +/// An error that occurs when a regex engine "gives up" for some reason before +/// finishing a search. Usually this occurs because of heuristic Unicode word +/// boundary support or because of ineffective cache usage in the lazy DFA. +/// +/// When this error occurs, callers should retry the regex search with a +/// different regex engine. +/// +/// Note that this has convenient `From` impls that will automatically +/// convert a `MatchError` into this error. This works because the meta +/// regex engine internals guarantee that errors like `HaystackTooLong` and +/// `UnsupportedAnchored` will never occur. The only errors left are `Quit` and +/// `GaveUp`, which both correspond to this "failure" error. +#[derive(Debug)] +pub(crate) struct RetryFailError { + offset: usize, +} + +impl RetryFailError { + pub(crate) fn from_offset(offset: usize) -> RetryFailError { + RetryFailError { offset } + } +} + +#[cfg(feature = "std")] +impl std::error::Error for RetryFailError {} + +impl core::fmt::Display for RetryFailError { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + write!(f, "regex engine failed at offset {:?}", self.offset) + } +} + +impl From<RetryFailError> for RetryError { + fn from(err: RetryFailError) -> RetryError { + RetryError::Fail(err) + } +} + +impl From<MatchError> for RetryFailError { + fn from(merr: MatchError) -> RetryFailError { + use crate::util::search::MatchErrorKind::*; + + match *merr.kind() { + Quit { offset, .. } => RetryFailError::from_offset(offset), + GaveUp { offset } => RetryFailError::from_offset(offset), + // These can never occur because we avoid them by construction + // or with higher level control flow logic. For example, the + // backtracker's wrapper will never hand out a backtracker engine + // when the haystack would be too long. + HaystackTooLong { .. } | UnsupportedAnchored { .. } => { + unreachable!("found impossible error in meta engine: {}", merr) + } + } + } +} |