errlanes 0.18.1

Four error lanes (Rejected/Denied/Transient/Fatal) carried in the type, not re-derived at every layer
Documentation 
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

use errlanes::{Lift, Rejection};

#[derive(Debug, errlanes::Rejection)]
enum Source {
    #[rejection(code = "SOURCE_VALUE", level = "warn")]
    Value(String),
}

// Rejection may read the mapping for metadata, but must not implement Lift/From.
#[derive(Debug, errlanes::Rejection)]
#[lift(Source)]
enum MetadataOnly {
    #[error("destination {0}")]
    #[lift(Source::Value)]
    Renamed(String),
}

impl From<Source> for MetadataOnly {
    fn from(source: Source) -> Self {
        let Source::Value(value) = source;
        Self::Renamed(value)
    }
}

#[test]
fn rejection_does_not_generate_conversions() {
    let rejection = MetadataOnly::lift(Source::Value("payload".into())).unwrap();
    assert_eq!(rejection.code().to_string(), "SOURCE_VALUE");
    assert_eq!(rejection.level(), errlanes::Level::Warn);
    assert_eq!(rejection.to_string(), "destination payload");
}

#[derive(Debug, errlanes::Rejection, errlanes::Lift)]
#[lift(Source)]
enum Forwarded {
    #[lift(Source::Value)]
    Renamed(String),
}

// Both derive orderings work: neither relies on the other's expansion.
#[derive(Debug, errlanes::Lift, errlanes::Rejection)]
#[lift(Source)]
enum Reinterpreted {
    #[lift(Source::Value)]
    #[rejection(code = "LOCAL_VALUE", level = "debug")]
    Renamed(String),
}

#[derive(Debug, errlanes::Rejection, errlanes::Lift)]
#[lift(Source)]
enum CodeOverride {
    #[lift(Source::Value)]
    #[rejection(code = "LOCAL_VALUE")]
    Renamed(String),
}

#[test]
fn simple_lift_forwards_metadata_unless_overridden() {
    let rejection = Forwarded::from(Source::Value("payload".into()));
    assert_eq!(rejection.code().to_string(), "SOURCE_VALUE");
    assert_eq!(rejection.level(), errlanes::Level::Warn);

    let rejection = Reinterpreted::from(Source::Value("payload".into()));
    assert_eq!(rejection.code().to_string(), "LOCAL_VALUE");
    assert_eq!(rejection.level(), errlanes::Level::Debug);

    let rejection = CodeOverride::from(Source::Value("payload".into()));
    assert_eq!(rejection.code().to_string(), "LOCAL_VALUE");
    assert_eq!(rejection.level(), errlanes::Level::Warn);
}

#[derive(Debug, errlanes::Rejection)]
enum ExplicitForward {
    #[rejection(code_and_level_from = Source::Value)]
    Renamed(String),
}

#[test]
fn explicit_metadata_forwarding_needs_no_lift() {
    let rejection = ExplicitForward::Renamed("payload".into());
    assert_eq!(rejection.code().to_string(), "SOURCE_VALUE");
    assert_eq!(rejection.level(), errlanes::Level::Warn);
}

#[derive(Debug, PartialEq)]
enum PartialInput {
    Accepted(u32),
    Unhandled(String),
}

#[derive(Debug, PartialEq, errlanes::Lift)]
#[lift(PartialInput, unhandled = fatal)]
enum PartialOutput {
    #[lift(PartialInput::Accepted)]
    Accepted(u32),
}

#[test]
fn partial_lift_alone_retains_the_unmapped_input() {
    assert_eq!(
        PartialOutput::lift(PartialInput::Accepted(3)),
        Ok(PartialOutput::Accepted(3))
    );
    assert_eq!(
        PartialOutput::lift(PartialInput::Unhandled("original".into())),
        Err(PartialInput::Unhandled("original".into())),
    );
}

// A whole-value arm: `Payload` is a struct source (not an enum variant), so
// `#[lift(Payload)]` with no variant suffix wraps the entire value. Lift
// sources are rejections, so `Payload` derives one.
#[derive(Debug, PartialEq, errlanes::Rejection)]
#[rejection(code = "INVALID_PAYLOAD")]
struct Payload(u32);

#[derive(Debug, PartialEq, errlanes::Lift)]
#[lift(Payload)]
enum JobRejection {
    #[lift(Payload)]
    InvalidPayload(Payload),
}

#[test]
fn whole_value_lift_wraps_a_struct_source_directly() {
    assert_eq!(
        JobRejection::from(Payload(7)),
        JobRejection::InvalidPayload(Payload(7))
    );
    assert_eq!(
        JobRejection::lift(Payload(7)),
        Ok(JobRejection::InvalidPayload(Payload(7)))
    );
}