Macro event

macro_rules! event {
    (target: $target:expr, $lvl:expr, { $( $($k:ident).+ = $val:expr ),* $(,)*} ) => { ... };
    (
        target: $target:expr,
        $lvl:expr,
        { $( $($k:ident).+ = $val:expr ),*, },
        $($arg:tt)+
    ) => { ... };
    (
        target: $target:expr,
        $lvl:expr,
        { $( $($k:ident).+ = $val:expr ),* },
        $($arg:tt)+
    ) => { ... };
    (target: $target:expr, $lvl:expr, $( $($k:ident).+ = $val:expr ),+, ) => { ... };
    (target: $target:expr, $lvl:expr, $( $($k:ident).+ = $val:expr ),+ ) => { ... };
    (target: $target:expr, $lvl:expr, $($arg:tt)+ ) => { ... };
    ( $lvl:expr, { $( $($k:ident).+ = $val:expr ),*, }, $($arg:tt)+ ) => { ... };
    ( $lvl:expr, { $( $($k:ident).+ = $val:expr ),* }, $($arg:tt)+ ) => { ... };
    ( $lvl:expr, $( $($k:ident).+ = $val:expr ),*, ) => { ... };
    ( $lvl:expr, $( $($k:ident).+ = $val:expr ),* ) => { ... };
    ( $lvl:expr, $($arg:tt)+ ) => { ... };
}

Constructs a new Event.

Examples

use tokio_trace::{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 span!, 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:

use tokio_trace::{Level, field};

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

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
);