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
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180

//! Stuff for error-handling.

use antidote::Mutex;
#[cfg(feature = "backtrace")]
use backtrace::Backtrace;
use std::{
    error::Error,
    fmt::{Debug, Display, Formatter, Result as FmtResult},
    mem::replace,
};

/// A convenient alias for `Result`.
pub type Result<T, E = Box<dyn Error + Send + Sync + 'static>> = ::std::result::Result<T, E>;

/// A wrapper for giving `ErrorKind`s causes and backtraces.
#[derive(Debug, Display)]
#[display(fmt = "{}", "kind")]
pub struct GenericError<T: Debug + Display> {
    kind: T,

    cause: Option<Box<dyn Error + 'static>>,

    // TODO: Don't derive Display if there's a backtrace.
    #[cfg(feature = "backtrace")]
    backtrace: Backtrace,
}

impl<T: Debug + Display> GenericError<T> {
    /// Returns the backtrace when the error was created.
    #[cfg(feature = "backtrace")]
    pub fn backtrace(&self) -> &Backtrace {
        &self.backtrace
    }

    /// Returns the kind of the error.
    pub fn kind(&self) -> &T {
        &self.kind
    }

    /// Creates an error with the given kind and cause.
    pub fn with_cause<C>(kind: T, cause: C) -> GenericError<T>
    where
        C: Into<Box<dyn Error + 'static>>,
    {
        GenericError {
            kind,
            cause: Some(cause.into()),
            #[cfg(feature = "backtrace")]
            backtrace: Backtrace::new(),
        }
    }
}

impl<T: Debug + Display> Error for GenericError<T> {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        self.cause.as_ref().map(|boxed| &**boxed)
    }
}

impl<T: Debug + Display> From<T> for GenericError<T> {
    fn from(kind: T) -> GenericError<T> {
        GenericError {
            kind,
            cause: None,
            #[cfg(feature = "backtrace")]
            backtrace: Backtrace::new(),
        }
    }
}

/// An iterator over the causes of an error.
#[derive(Debug)]
pub struct ErrorCauseIter<'a>(Option<&'a (dyn Error + 'static)>);

impl<'a> From<&'a (dyn Error + 'static)> for ErrorCauseIter<'a> {
    fn from(err: &'a (dyn Error + 'static)) -> ErrorCauseIter<'a> {
        ErrorCauseIter(Some(err))
    }
}

impl<'a> Iterator for ErrorCauseIter<'a> {
    type Item = &'a dyn Error;

    fn next(&mut self) -> Option<&'a dyn Error> {
        let err = self.0?;
        self.0 = err.source();
        Some(err)
    }
}

// All the commented stuff will work on rustc 1.35.0+.

trait EFunc: Send {
    fn make_string(self: Box<Self>) -> String;
}

impl<F: FnOnce() -> String + Send> EFunc for F {
    fn make_string(self: Box<Self>) -> String {
        self()
    }
}

/// An error that is a wrapper around a `Formatter`.
pub struct E(Mutex<Result<String, Box<dyn EFunc>>>);
// pub struct E(Mutex<Result<String, Box<dyn FnOnce() -> String>>>);

impl E {
    fn as_string(&self) -> String {
        let mut lock = self.0.lock();
        match replace(&mut *lock, Ok("[panicked]".to_string())) {
            Ok(_) => {}
            // Err(func) => *lock = Ok(func()),
            Err(func) => *lock = Ok(func.make_string()),
        }
        match lock.as_ref() {
            Ok(s) => s.clone(),
            Err(_) => unreachable!(),
        }
    }

    #[doc(hidden)]
    pub fn from_closure<F: 'static + FnOnce() -> String + Send>(f: F) -> E {
        E(Mutex::new(Err(Box::new(f))))
    }
}

impl Debug for E {
    fn fmt(&self, fmt: &mut Formatter) -> FmtResult {
        fmt.write_str(&self.as_string())
    }
}

impl Display for E {
    fn fmt(&self, fmt: &mut Formatter) -> FmtResult {
        fmt.write_str(&self.as_string())
    }
}

impl Error for E {}

/// Creates an instance of `E` as a `Box<dyn Error>`.
///
/// ```rust
/// # use libremexre::err;
/// # use std::error::Error;
/// let e: Box<dyn Error> = err!("foo {} bar", 1);
/// assert_eq!(e.to_string(), "foo 1 bar");
/// ```
#[macro_export]
macro_rules! err {
    ($($tt:tt)*) => {{
        let e = $crate::errors::E::from_closure(move || std::format!($($tt)*));
        let e: std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync> =
            std::boxed::Box::new(e);
        e
    }};
}

/// Logs an error, including its causes.
#[cfg(feature = "log")]
pub fn log_err(err: &(dyn Error + 'static)) {
    use log::error;

    // Count the number of errors.
    let num_errs = ErrorCauseIter::from(err).count();

    if num_errs <= 1 {
        error!("{}", err);
    } else {
        let mut first = true;
        for err in ErrorCauseIter::from(err) {
            if first {
                first = false;
                error!("           {}", err);
            } else {
                error!("caused by: {}", err);
            }
        }
    }
}