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

//! `target()` predicate factory.

use predicates::{
    reflection::{Case, PredicateReflection, Product},
    Predicate,
};

use std::fmt;

use crate::Captured;

/// Conversion into a predicate for the target used in the [`target()`] function.
pub trait IntoTargetPredicate {
    /// Predicate output of the conversion. The exact type should be considered an implementation
    /// detail and should not be relied upon.
    type Predicate: Predicate<str>;
    /// Performs the conversion.
    fn into_predicate(self) -> Self::Predicate;
}

impl<P: Predicate<str>> IntoTargetPredicate for [P; 1] {
    type Predicate = P;

    fn into_predicate(self) -> Self::Predicate {
        self.into_iter().next().unwrap()
    }
}

impl<'a> IntoTargetPredicate for &'a str {
    type Predicate = TargetStrPredicate<'a>;

    fn into_predicate(self) -> Self::Predicate {
        TargetStrPredicate { prefix: self }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TargetStrPredicate<'a> {
    prefix: &'a str,
}

impl fmt::Display for TargetStrPredicate<'_> {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "target ^= {}", self.prefix)
    }
}

impl PredicateReflection for TargetStrPredicate<'_> {}

impl Predicate<str> for TargetStrPredicate<'_> {
    fn eval(&self, variable: &str) -> bool {
        variable
            .strip_prefix(self.prefix)
            .map_or(false, |stripped| {
                stripped.is_empty() || stripped.starts_with("::")
            })
    }

    fn find_case(&self, expected: bool, variable: &str) -> Option<Case<'_>> {
        if self.eval(variable) == expected {
            let product = Product::new("target", variable.to_owned());
            Some(Case::new(Some(self), expected).add_product(product))
        } else {
            None
        }
    }
}

/// Creates a predicate for the target of a [`CapturedSpan`] or [`CapturedEvent`].
///
/// # Arguments
///
/// The argument of this function may be:
///
/// - `&str`: will be compared as per standard target filtering. E.g., `target("tracing")`
///   will match `tracing` and `tracing::predicate` targets, but not `tracing_capture`.
/// - Any `str` `Predicate`. To bypass Rust orphaning rules, the predicate
///   must be enclosed in square brackets (i.e., a one-value array).
///
/// [`CapturedSpan`]: crate::CapturedSpan
/// [`CapturedEvent`]: crate::CapturedEvent
///
/// # Examples
///
/// ```
/// # use predicates::str::starts_with;
/// # use tracing_subscriber::{layer::SubscriberExt, Registry};
/// # use tracing_capture::{predicates::{target, ScanExt}, CaptureLayer, SharedStorage};
/// let storage = SharedStorage::default();
/// let subscriber = Registry::default().with(CaptureLayer::new(&storage));
/// tracing::subscriber::with_default(subscriber, || {
///     tracing::info_span!(target: "capture::test", "compute").in_scope(|| {
///         tracing::info!(answer = 42, "done");
///     });
/// });
///
/// let storage = storage.lock();
/// // All of these access the single captured span.
/// let spans = storage.scan_spans();
/// let _ = spans.single(&target("capture"));
/// let _ = spans.single(&target([starts_with("cap")]));
/// ```
pub fn target<P: IntoTargetPredicate>(matches: P) -> TargetPredicate<P::Predicate> {
    TargetPredicate {
        matches: matches.into_predicate(),
    }
}

/// Predicate for the target of a [`CapturedSpan`] or [`CapturedEvent`] returned by
/// the [`target()`] function.
///
/// [`CapturedSpan`]: crate::CapturedSpan
/// [`CapturedEvent`]: crate::CapturedEvent
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TargetPredicate<P> {
    matches: P,
}

impl_bool_ops!(TargetPredicate<P>);

impl<P: Predicate<str>> fmt::Display for TargetPredicate<P> {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "target({})", self.matches)
    }
}

impl<P: Predicate<str>> PredicateReflection for TargetPredicate<P> {}

impl<'a, P: Predicate<str>, T: Captured<'a>> Predicate<T> for TargetPredicate<P> {
    fn eval(&self, variable: &T) -> bool {
        self.matches.eval(variable.metadata().target())
    }

    fn find_case(&self, expected: bool, variable: &T) -> Option<Case<'_>> {
        let child = self
            .matches
            .find_case(expected, variable.metadata().target())?;
        Some(Case::new(Some(self), expected).add_child(child))
    }
}