Macro tracing::event

macro_rules! event {
    (target: $target:expr, parent: $parent:expr, $lvl:expr, { $($fields:tt)* } ) => { ... };
    (target: $target:expr, parent: $parent:expr, $lvl:expr,  { $($fields:tt)* }, $($arg:tt)+ ) => { ... };
    (target: $target:expr, parent: $parent:expr, $lvl:expr, $($k:ident).+ = $($fields:tt)* ) => { ... };
    (target: $target:expr, parent: $parent:expr, $lvl:expr, $($arg:tt)+ ) => { ... };
    (target: $target:expr, $lvl:expr, { $($fields:tt)* } ) => { ... };
    (target: $target:expr, $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => { ... };
    (target: $target:expr, $lvl:expr, $($k:ident).+ = $($fields:tt)* ) => { ... };
    (target: $target:expr, $lvl:expr, $($arg:tt)+ ) => { ... };
    (parent: $parent:expr, $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => { ... };
    (parent: $parent:expr, $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => { ... };
    (parent: $parent:expr, $lvl:expr, $($k:ident).+ = $($field:tt)*) => { ... };
    (parent: $parent:expr, $lvl:expr, ?$($k:ident).+ = $($field:tt)*) => { ... };
    (parent: $parent:expr, $lvl:expr, %$($k:ident).+ = $($field:tt)*) => { ... };
    (parent: $parent:expr, $lvl:expr, $($k:ident).+, $($field:tt)*) => { ... };
    (parent: $parent:expr, $lvl:expr, %$($k:ident).+, $($field:tt)*) => { ... };
    (parent: $parent:expr, $lvl:expr, ?$($k:ident).+, $($field:tt)*) => { ... };
    (parent: $parent:expr, $lvl:expr, $($arg:tt)+ ) => { ... };
    ( $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => { ... };
    ( $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => { ... };
    ($lvl:expr, $($k:ident).+ = $($field:tt)*) => { ... };
    ($lvl:expr, $($k:ident).+, $($field:tt)*) => { ... };
    ($lvl:expr, ?$($k:ident).+, $($field:tt)*) => { ... };
    ($lvl:expr, %$($k:ident).+, $($field:tt)*) => { ... };
    ($lvl:expr, ?$($k:ident).+) => { ... };
    ($lvl:expr, %$($k:ident).+) => { ... };
    ($lvl:expr, $($k:ident).+) => { ... };
    ( $lvl:expr, $($arg:tt)+ ) => { ... };
}

Constructs a new Event.

Examples

use tracing::{Level, field};

let data = (42, "fourty-two");
let private_data = "private";
let error = "a bad error";

event!(Level::ERROR, { error = field::display(error) }, "Received error");
event!(target: "app_events", Level::WARN, {
        private_data = private_data,
        data = field::debug(data),
    },
    "App warning: {}", error
);
event!(Level::INFO, the_answer = data.0);

Note that unlike $crate::span!, $crate::event! requires a value for all fields. As events are recorded immediately when the macro is invoked, there is no opportunity for fields to be recorded later. A trailing comma on the final field is valid.

For example, the following does not compile:

event!(Level::Info, foo = 5, bad_field, bar = "hello")
#}

Shorthand for field::debug:

#[derive(Debug)]
struct MyStruct {
    field: &'static str,
}

let my_struct = MyStruct {
    field: "Hello world!"
};

// `my_struct` will be recorded using its `fmt::Debug` implementation.
event!(Level::TRACE, my_struct = ?my_struct);

Shorthand for field::display:

// `my_struct.field` will be recorded using its `fmt::Display` implementation.
event!(Level::TRACE, my_struct.field = %my_struct.field);

Events may have up to 32 fields. The following will not compile:

event!(Level::INFO,
    a = 1, b = 2, c = 3, d = 4, e = 5, f = 6, g = 7, h = 8, i = 9,
    j = 10, k = 11, l = 12, m = 13, n = 14, o = 15, p = 16, q = 17,
    r = 18, s = 19, t = 20, u = 21, v = 22, w = 23, x = 24, y = 25,
    z = 26, aa = 27, bb = 28, cc = 29, dd = 30, ee = 31, ff = 32, gg = 33
);