      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
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279

    //! Core primitives for `tracing`.
    //!
    //! [`tracing`] is a framework for instrumenting Rust programs to collect
    //! structured, event-based diagnostic information. This crate defines the core
    //! primitives of `tracing`.
    //!
    //! This crate provides:
    //!
    //! * [`span::Id`] identifies a span within the execution of a program.
    //!
    //! * [`Event`] represents a single event within a trace.
    //!
    //! * [`Subscriber`], the trait implemented to collect trace data.
    //!
    //! * [`Metadata`] and [`Callsite`] provide information describing spans and
    //!   `Event`s.
    //!
    //! * [`Field`], [`FieldSet`], [`Value`], and [`ValueSet`] represent the
    //!   structured data attached to a span.
    //!
    //! * [`Dispatch`] allows spans and events to be dispatched to `Subscriber`s.
    //!
    //! In addition, it defines the global callsite registry and per-thread current
    //! dispatcher which other components of the tracing system rely on.
    //!
    //! *Compiler support: [requires `rustc` 1.40+][msrv]*
    //!
    //! [msrv]: #supported-rust-versions
    //!
    //! ## Usage
    //!
    //! Application authors will typically not use this crate directly. Instead,
    //! they will use the [`tracing`] crate, which provides a much more
    //! fully-featured API. However, this crate's API will change very infrequently,
    //! so it may be used when dependencies must be very stable.
    //!
    //! `Subscriber` implementations may depend on `tracing-core` rather than
    //! `tracing`, as the additional APIs provided by `tracing` are primarily useful
    //! for instrumenting libraries and applications, and are generally not
    //! necessary for `Subscriber` implementations.
    //!
    //! The [`tokio-rs/tracing`] repository contains less stable crates designed to
    //! be used with the `tracing` ecosystem. It includes a collection of
    //! `Subscriber` implementations, as well as utility and adapter crates.
    //!
    //! ### Crate Feature Flags
    //!
    //! The following crate feature flags are available:
    //!
    //! * `std`: Depend on the Rust standard library (enabled by default).
    //!
    //!   `no_std` users may disable this feature with `default-features = false`:
    //!
    //!   ```toml
    //!   [dependencies]
    //!   tracing-core = { version = "0.1.17", default-features = false }
    //!   ```
    //!
    //!   **Note**:`tracing-core`'s `no_std` support requires `liballoc`.
    //!
    //! ## Supported Rust Versions
    //!
    //! Tracing is built against the latest stable release. The minimum supported
    //! version is 1.40. The current Tracing version is not guaranteed to build on
    //! Rust versions earlier than the minimum supported version.
    //!
    //! Tracing follows the same compiler support policies as the rest of the Tokio
    //! project. The current stable Rust compiler and the three most recent minor
    //! versions before it will always be supported. For example, if the current
    //! stable compiler version is 1.45, the minimum supported version will not be
    //! increased past 1.42, three minor versions prior. Increasing the minimum
    //! supported compiler version is not considered a semver breaking change as
    //! long as doing so complies with this policy.
    //!
    //!
    //! [`span::Id`]: span/struct.Id.html
    //! [`Event`]: event/struct.Event.html
    //! [`Subscriber`]: subscriber/trait.Subscriber.html
    //! [`Metadata`]: metadata/struct.Metadata.html
    //! [`Callsite`]: callsite/trait.Callsite.html
    //! [`Field`]: field/struct.Field.html
    //! [`FieldSet`]: field/struct.FieldSet.html
    //! [`Value`]: field/trait.Value.html
    //! [`ValueSet`]: field/struct.ValueSet.html
    //! [`Dispatch`]: dispatcher/struct.Dispatch.html
    //! [`tokio-rs/tracing`]: https://github.com/tokio-rs/tracing
    //! [`tracing`]: https://crates.io/crates/tracing
    #![doc(html_root_url = "https://docs.rs/tracing-core/0.1.17")]
    #![doc(
        html_logo_url = "https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png",
        issue_tracker_base_url = "https://github.com/tokio-rs/tracing/issues/"
    )]
    #![cfg_attr(not(feature = "std"), no_std)]
    #![cfg_attr(docsrs, feature(doc_cfg), deny(broken_intra_doc_links))]
    #![warn(
        missing_debug_implementations,
        missing_docs,
        rust_2018_idioms,
        unreachable_pub,
        bad_style,
        const_err,
        dead_code,
        improper_ctypes,
        non_shorthand_field_patterns,
        no_mangle_generic_items,
        overflowing_literals,
        path_statements,
        patterns_in_fns_without_body,
        private_in_public,
        unconditional_recursion,
        unused,
        unused_allocation,
        unused_comparisons,
        unused_parens,
        while_true
    )]
    #[cfg(not(feature = "std"))]
    extern crate alloc;

    /// Statically constructs an [`Identifier`] for the provided [`Callsite`].
    ///
    /// This may be used in contexts, such as static initializers, where the
    /// [`Callsite::id`] function is not currently usable.
    ///
    /// For example:
    /// ```rust
    /// # #[macro_use]
    /// # extern crate tracing_core;
    /// use tracing_core::callsite;
    /// # use tracing_core::{Metadata, subscriber::Interest};
    /// # fn main() {
    /// pub struct MyCallsite {
    ///    // ...
    /// }
    /// impl callsite::Callsite for MyCallsite {
    /// # fn set_interest(&self, _: Interest) { unimplemented!() }
    /// # fn metadata(&self) -> &Metadata { unimplemented!() }
    ///     // ...
    /// }
    ///
    /// static CALLSITE: MyCallsite = MyCallsite {
    ///     // ...
    /// };
    ///
    /// static CALLSITE_ID: callsite::Identifier = identify_callsite!(&CALLSITE);
    /// # }
    /// ```
    ///
    /// [`Identifier`]: callsite/struct.Identifier.html
    /// [`Callsite`]: callsite/trait.Callsite.html
    /// [`Callsite::id`]: callsite/trait.Callsite.html#method.id
    #[macro_export]
    macro_rules! identify_callsite {
        ($callsite:expr) => {
            $crate::callsite::Identifier($callsite)
        };
    }

    /// Statically constructs new span [metadata].
    ///
    /// /// For example:
    /// ```rust
    /// # #[macro_use]
    /// # extern crate tracing_core;
    /// # use tracing_core::{callsite::Callsite, subscriber::Interest};
    /// use tracing_core::metadata::{Kind, Level, Metadata};
    /// # fn main() {
    /// # pub struct MyCallsite { }
    /// # impl Callsite for MyCallsite {
    /// # fn set_interest(&self, _: Interest) { unimplemented!() }
    /// # fn metadata(&self) -> &Metadata { unimplemented!() }
    /// # }
    /// #
    /// static FOO_CALLSITE: MyCallsite = MyCallsite {
    ///     // ...
    /// };
    ///
    /// static FOO_METADATA: Metadata = metadata!{
    ///     name: "foo",
    ///     target: module_path!(),
    ///     level: Level::DEBUG,
    ///     fields: &["bar", "baz"],
    ///     callsite: &FOO_CALLSITE,
    ///     kind: Kind::SPAN,
    /// };
    /// # }
    /// ```
    ///
    /// [metadata]: metadata/struct.Metadata.html
    /// [`Metadata::new`]: metadata/struct.Metadata.html#method.new
    #[macro_export]
    macro_rules! metadata {
        (
            name: $name:expr,
            target: $target:expr,
            level: $level:expr,
            fields: $fields:expr,
            callsite: $callsite:expr,
            kind: $kind:expr
        ) => {
            $crate::metadata! {
                name: $name,
                target: $target,
                level: $level,
                fields: $fields,
                callsite: $callsite,
                kind: $kind,
            }
        };
        (
            name: $name:expr,
            target: $target:expr,
            level: $level:expr,
            fields: $fields:expr,
            callsite: $callsite:expr,
            kind: $kind:expr,
        ) => {
            $crate::metadata::Metadata::new(
                $name,
                $target,
                $level,
                Some(file!()),
                Some(line!()),
                Some(module_path!()),
                $crate::field::FieldSet::new($fields, $crate::identify_callsite!($callsite)),
                $kind,
            )
        };
    }

    // std uses lazy_static from crates.io
    #[cfg(feature = "std")]
    #[macro_use]
    extern crate lazy_static;

    // no_std uses vendored version of lazy_static 1.4.0 (4216696) with spin
    // This can conflict when included in a project already using std lazy_static
    // Remove this module when cargo enables specifying dependencies for no_std
    #[cfg(not(feature = "std"))]
    #[macro_use]
    mod lazy_static;

    // Trimmed-down vendored version of spin 0.5.2 (0387621)
    // Dependency of no_std lazy_static, not required in a std build
    #[cfg(not(feature = "std"))]
    pub(crate) mod spin;

    #[cfg(not(feature = "std"))]
    #[doc(hidden)]
    pub type Once = self::spin::Once<()>;

    #[cfg(feature = "std")]
    pub use stdlib::sync::Once;

    pub mod callsite;
    pub mod dispatcher;
    pub mod event;
    pub mod field;
    pub mod metadata;
    mod parent;
    pub mod span;
    pub(crate) mod stdlib;
    pub mod subscriber;

    #[doc(inline)]
    pub use self::{
        callsite::Callsite,
        dispatcher::Dispatch,
        event::Event,
        field::Field,
        metadata::{Level, LevelFilter, Metadata},
        subscriber::Subscriber,
    };

    pub use self::{metadata::Kind, subscriber::Interest};

    mod sealed {
        pub trait Sealed {}
    }