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

use std::{fmt, io};

pub(crate) type Result<T, E = Error> = std::result::Result<T, E>;

#[derive(Debug)]
pub struct Error(ErrorKind);

// Hiding error variants from a library's public error type to prevent
// dependency updates from becoming breaking changes.
// We can add `is_*` methods that indicate the kind of error if needed, but
// don't expose dependencies' types directly in the public API.
#[derive(Debug)]
pub(crate) enum ErrorKind {
    Io(io::Error),

    Process(crate::process::ProcessError),

    Json(serde_json::Error),

    WithContext(String, Option<Box<dyn std::error::Error + Send + Sync + 'static>>),
}

impl Error {
    pub(crate) fn new(e: impl Into<ErrorKind>) -> Self {
        Self(e.into())
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match &self.0 {
            ErrorKind::Io(e) => fmt::Display::fmt(e, f),
            ErrorKind::Process(e) => fmt::Display::fmt(e, f),
            ErrorKind::Json(e) => fmt::Display::fmt(e, f),
            ErrorKind::WithContext(e, ..) => fmt::Display::fmt(e, f),
        }
    }
}

impl std::error::Error for Error {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match &self.0 {
            ErrorKind::Io(e) => e.source(),
            ErrorKind::Process(e) => e.source(),
            ErrorKind::Json(e) => e.source(),
            ErrorKind::WithContext(_, e) => Some(&**e.as_ref()?),
        }
    }
}

impl From<io::Error> for ErrorKind {
    fn from(e: io::Error) -> Self {
        Self::Io(e)
    }
}
impl From<crate::process::ProcessError> for ErrorKind {
    fn from(e: crate::process::ProcessError) -> Self {
        Self::Process(e)
    }
}
impl From<serde_json::Error> for ErrorKind {
    fn from(e: serde_json::Error) -> Self {
        Self::Json(e)
    }
}

// Note: Do not implement From<ThirdPartyErrorType> to prevent dependency
// updates from becoming breaking changes.
// Implementing `From<StdErrorType>` should also be avoided whenever possible,
// as it would be a breaking change to remove the implementation if the
// conversion is no longer needed due to changes in the internal implementation.

// Inspired by anyhow::Context.
pub(crate) trait Context<T, E> {
    fn context<C>(self, context: C) -> Result<T, Error>
    where
        C: fmt::Display;
    fn with_context<C, F>(self, context: F) -> Result<T, Error>
    where
        C: fmt::Display,
        F: FnOnce() -> C;
}
impl<T, E> Context<T, E> for Result<T, E>
where
    E: std::error::Error + Send + Sync + 'static,
{
    fn context<C>(self, context: C) -> Result<T, Error>
    where
        C: fmt::Display,
    {
        match self {
            Ok(ok) => Ok(ok),
            Err(e) => Err(Error(ErrorKind::WithContext(context.to_string(), Some(Box::new(e))))),
        }
    }
    fn with_context<C, F>(self, context: F) -> Result<T, Error>
    where
        C: fmt::Display,
        F: FnOnce() -> C,
    {
        match self {
            Ok(ok) => Ok(ok),
            Err(e) => Err(Error(ErrorKind::WithContext(context().to_string(), Some(Box::new(e))))),
        }
    }
}
impl<T> Context<T, std::convert::Infallible> for Option<T> {
    fn context<C>(self, context: C) -> Result<T, Error>
    where
        C: fmt::Display,
    {
        match self {
            Some(ok) => Ok(ok),
            None => Err(Error(ErrorKind::WithContext(context.to_string(), None))),
        }
    }
    fn with_context<C, F>(self, context: F) -> Result<T, Error>
    where
        C: fmt::Display,
        F: FnOnce() -> C,
    {
        match self {
            Some(ok) => Ok(ok),
            None => Err(Error(ErrorKind::WithContext(context().to_string(), None))),
        }
    }
}