user_backtrace/
lib.rs

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
use std::fmt::{Display, Formatter};

const HIDDEN_PACKAGES: &[&str] = &[
    "F",
    "alloc",
    "anyhow",
    "axum",
    "backtrace",
    "core",
    "futures",
    "futures_core",
    "futures_util",
    "hyper",
    "hyper_util",
    "std",
    "test",
    "tokio",
    "tower",
    "tower_service",
    "tracing",
];

pub struct DecodedFrame {
    frame: String,
    location: Option<String>,
}

/// Represents a best attempt at pulling out only user relevant information from a backtrace frame.
pub enum DecodedUserBacktrace {
    Frames(Vec<DecodedFrame>),
    Disabled,
}

impl Display for DecodedUserBacktrace {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            DecodedUserBacktrace::Frames(frames) => {
                for frame in frames {
                    writeln!(f, "{}", frame.frame)?;
                    if let Some(line2) = &frame.location {
                        writeln!(f, "{}", line2)?;
                    }
                }
                Ok(())
            }
            DecodedUserBacktrace::Disabled => {
                writeln!(f, "disabled backtrace")
            }
        }
    }
}

fn decode_backtrace<Backtrace: Display>(
    b: &Backtrace,
    hide_packages: &[&str],
) -> DecodedUserBacktrace {
    let s = b.to_string();
    let mut lines = s.lines().peekable();
    let mut frames = Vec::new();
    if lines
        .peek()
        .map(|&s| s == "disabled backtrace")
        .unwrap_or(true)
    {
        return DecodedUserBacktrace::Disabled;
    }

    loop {
        let Some(&line) = lines.peek() else {
            break;
        };
        let line = &line[3..];
        if line.starts_with('1') {
            break;
        }
        lines.next();
    }

    while let Some(frame) = lines.next() {
        // skip the "  #: " portion
        let frame = &frame[6..];
        if frame.starts_with("__") {
            continue;
        }
        // get location, if its there
        let mut location = None;
        if let Some(&l) = lines.peek() {
            let l = l.trim_start_matches(' ');
            if l.starts_with("at ") {
                location = Some(lines.next().unwrap().to_string());
            }
        }

        if frame.starts_with("start_thread") || frame.starts_with("clone") {
            continue;
        }

        // decode
        if frame.starts_with('<') {
            let (left, right) = frame[1..].split_once(" as ").unwrap();
            let package1 = left.split(':').next().unwrap();
            let package2 = right.split(':').next().unwrap();
            if hide_packages.contains(&package1) && hide_packages.contains(&package2) {
                continue;
            }
        } else {
            let package = frame.split(':').next().unwrap();
            if hide_packages.contains(&package) {
                continue;
            }
        };
        frames.push(DecodedFrame {
            frame: frame.to_string(),
            location,
        });
    }
    DecodedUserBacktrace::Frames(frames)
}

pub trait UserBacktrace {
    fn user_backtrace(&self) -> DecodedUserBacktrace;
}

impl UserBacktrace for anyhow::Error {
    fn user_backtrace(&self) -> DecodedUserBacktrace {
        decode_backtrace(self.backtrace(), HIDDEN_PACKAGES)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use anyhow::{anyhow, Result};

    fn nested2() -> Result<()> {
        Err(anyhow!("Not implemented"))
    }

    fn nested1() -> Result<()> {
        nested2()
    }

    #[test]
    fn test_anyhow_err() {
        let Err(e) = nested1() else {
            panic!("expected error");
        };
        // println!("{:?}", decode_backtrace(e.backtrace()));
        println!("backtrace: {}", e.backtrace());
        let user_backtrace = format!("{}", e.user_backtrace());
        println!("{}", user_backtrace);
        assert_eq!(user_backtrace.lines().count(), 8);
    }

    #[test]
    fn test_parse_backtrace1() {
        let s = include_str!("../data/backtrace1.txt");
        let r = decode_backtrace(&s, HIDDEN_PACKAGES);
        let r = r.to_string();
        println!("{}", r);
        assert_eq!(r.lines().count(), 3);
    }
}