regex/
error.rs

1use alloc::string::{String, ToString};
2
3use regex_automata::meta;
4
5/// An error that occurred during parsing or compiling a regular expression.
6#[non_exhaustive]
7#[derive(Clone, PartialEq)]
8pub enum Error {
9    /// A syntax error.
10    Syntax(String),
11    /// The compiled program exceeded the set size
12    /// limit. The argument is the size limit imposed by
13    /// [`RegexBuilder::size_limit`](crate::RegexBuilder::size_limit). Even
14    /// when not configured explicitly, it defaults to a reasonable limit.
15    ///
16    /// If you're getting this error, it occurred because your regex has been
17    /// compiled to an intermediate state that is too big. It is important to
18    /// note that exceeding this limit does _not_ mean the regex is too big to
19    /// _work_, but rather, the regex is big enough that it may wind up being
20    /// surprisingly slow when used in a search. In other words, this error is
21    /// meant to be a practical heuristic for avoiding a performance footgun,
22    /// and especially so for the case where the regex pattern is coming from
23    /// an untrusted source.
24    ///
25    /// There are generally two ways to move forward if you hit this error.
26    /// The first is to find some way to use a smaller regex. The second is to
27    /// increase the size limit via `RegexBuilder::size_limit`. However, if
28    /// your regex pattern is not from a trusted source, then neither of these
29    /// approaches may be appropriate. Instead, you'll have to determine just
30    /// how big of a regex you want to allow.
31    CompiledTooBig(usize),
32}
33
34impl Error {
35    pub(crate) fn from_meta_build_error(err: meta::BuildError) -> Error {
36        if let Some(size_limit) = err.size_limit() {
37            Error::CompiledTooBig(size_limit)
38        } else if let Some(ref err) = err.syntax_error() {
39            Error::Syntax(err.to_string())
40        } else {
41            // This is a little suspect. Technically there are more ways for
42            // a meta regex to fail to build other than "exceeded size limit"
43            // and "syntax error." For example, if there are too many states
44            // or even too many patterns. But in practice this is probably
45            // good enough. The worst thing that happens is that Error::Syntax
46            // represents an error that isn't technically a syntax error, but
47            // the actual message will still be shown. So... it's not too bad.
48            //
49            // We really should have made the Error type in the regex crate
50            // completely opaque. Rookie mistake.
51            Error::Syntax(err.to_string())
52        }
53    }
54}
55
56#[cfg(feature = "std")]
57impl std::error::Error for Error {
58    // TODO: Remove this method entirely on the next breaking semver release.
59    #[allow(deprecated)]
60    fn description(&self) -> &str {
61        match *self {
62            Error::Syntax(ref err) => err,
63            Error::CompiledTooBig(_) => "compiled program too big",
64        }
65    }
66}
67
68impl core::fmt::Display for Error {
69    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
70        match *self {
71            Error::Syntax(ref err) => err.fmt(f),
72            Error::CompiledTooBig(limit) => write!(
73                f,
74                "Compiled regex exceeds size limit of {} bytes.",
75                limit
76            ),
77        }
78    }
79}
80
81// We implement our own Debug implementation so that we show nicer syntax
82// errors when people use `Regex::new(...).unwrap()`. It's a little weird,
83// but the `Syntax` variant is already storing a `String` anyway, so we might
84// as well format it nicely.
85impl core::fmt::Debug for Error {
86    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
87        match *self {
88            Error::Syntax(ref err) => {
89                let hr: String = core::iter::repeat('~').take(79).collect();
90                writeln!(f, "Syntax(")?;
91                writeln!(f, "{}", hr)?;
92                writeln!(f, "{}", err)?;
93                writeln!(f, "{}", hr)?;
94                write!(f, ")")?;
95                Ok(())
96            }
97            Error::CompiledTooBig(limit) => {
98                f.debug_tuple("CompiledTooBig").field(&limit).finish()
99            }
100        }
101    }
102}
regex/error.rs

regex/
error.rs
