1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#[cfg(feature = "backtrace")]
/// Re-export of the `backtrace` crate for use in macros and
/// to ensure the needed version is kept in sync in dependents.
pub use backtrace;

#[cfg(not(feature = "backtrace"))]
/// A compatibility shim for `backtrace`.
pub mod backtrace {
    use std::fmt;

    pub struct Backtrace;

    impl fmt::Debug for Backtrace {
        #[cold]
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "Not available")
        }
    }
}

/// Define a wrapper around the the provided ErrorKind type.
/// See also `define_error` which is more likely to be what you want.
#[macro_export]
macro_rules! define_error_wrapper {
    ($Kind:ty) => {
        pub type Result<T, E = Error> = std::result::Result<T, E>;
        struct ErrorData {
            kind: $Kind,
            backtrace: Option<std::sync::Mutex<$crate::backtrace::Backtrace>>,
        }

        impl ErrorData {
            #[cold]
            fn new(kind: $Kind) -> Self {
                ErrorData {
                    kind,
                    #[cfg(feature = "backtrace")]
                    backtrace: Some(std::sync::Mutex::new(
                        $crate::backtrace::Backtrace::new_unresolved(),
                    )),
                    #[cfg(not(feature = "backtrace"))]
                    backtrace: None,
                }
            }

            #[cfg(feature = "backtrace")]
            #[cold]
            fn get_backtrace(&self) -> Option<&std::sync::Mutex<$crate::backtrace::Backtrace>> {
                self.backtrace.as_ref().map(|mutex| {
                    mutex.lock().unwrap().resolve();
                    mutex
                })
            }

            #[cfg(not(feature = "backtrace"))]
            #[cold]
            fn get_backtrace(&self) -> Option<&std::sync::Mutex<$crate::backtrace::Backtrace>> {
                None
            }
        }

        impl std::fmt::Debug for ErrorData {
            #[cfg(feature = "backtrace")]
            #[cold]
            fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
                let mut bt = self.backtrace.unwrap().lock().unwrap();
                bt.resolve();
                write!(f, "{:?}\n\n{}", bt, self.kind)
            }

            #[cfg(not(feature = "backtrace"))]
            #[cold]
            fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
                write!(f, "{}", self.kind)
            }
        }

        #[derive(Debug, thiserror::Error)]
        pub struct Error(Box<ErrorData>);
        impl Error {
            #[cold]
            pub fn kind(&self) -> &$Kind {
                &self.0.kind
            }

            #[cold]
            pub fn backtrace(&self) -> Option<&std::sync::Mutex<$crate::backtrace::Backtrace>> {
                self.0.get_backtrace()
            }
        }

        impl std::fmt::Display for Error {
            #[cold]
            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                std::fmt::Display::fmt(self.kind(), f)
            }
        }

        impl From<$Kind> for Error {
            // Cold to optimize in favor of non-error cases.
            #[cold]
            fn from(ctx: $Kind) -> Error {
                Error(Box::new(ErrorData::new(ctx)))
            }
        }
    };
}

/// Define a set of conversions from external error types into the provided
/// error kind. Use `define_error` to do this at the same time as
/// `define_error_wrapper`.
#[macro_export]
macro_rules! define_error_conversions {
    ($Kind:ident { $(($variant:ident, $type:ty)),* $(,)? }) => ($(
        impl From<$type> for Error {
            // Cold to optimize in favor of non-error cases.
            #[cold]
            fn from(e: $type) -> Self {
                Error::from($Kind::$variant(e))
            }
        }
    )*);
}

/// All the error boilerplate (okay, with a couple exceptions in some cases) in
/// one place.
#[macro_export]
macro_rules! define_error {
    ($Kind:ident { $(($variant:ident, $type:ty)),* $(,)? }) => {
        $crate::define_error_wrapper!($Kind);
        $crate::define_error_conversions! {
            $Kind {
                $(($variant, $type)),*
            }
        }
    };
}