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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
//! A Rust tracing layer that forwards events to Gecko logging: MOZ_LOG output on
//! stderr or MOZ_LOG_FILE, plus a LOGS profiler marker, as a C++ `MOZ_LOG`
//! call produces.
use tracing::{subscriber::Interest, Event, Level, Metadata, Subscriber};
use tracing_subscriber::layer::{Context, Filter, Layer};
use crate::fields::FieldFormatter;
fn to_log_level(level: Level) -> log::Level {
match level {
Level::ERROR => log::Level::Error,
Level::WARN => log::Level::Warn,
Level::INFO => log::Level::Info,
Level::DEBUG => log::Level::Debug,
Level::TRACE => log::Level::Trace,
}
}
/// Whether MOZ_LOG enables the callsite's target at its level, like
/// `MOZ_LOG_TEST` in C++.
pub(crate) fn moz_log_test(meta: &Metadata<'_>) -> bool {
gecko_logger::moz_log_test(meta.target(), to_log_level(*meta.level()))
}
/// Filters events by the MOZ_LOG level of their target.
pub struct MozLogFilter;
impl MozLogFilter {
fn is_enabled(meta: &Metadata<'_>) -> bool {
meta.is_event() && moz_log_test(meta)
}
}
impl<S> Filter<S> for MozLogFilter {
// Cached per callsite, and rebuilt by gecko_logger when MOZ_LOG changes.
fn callsite_enabled(&self, meta: &'static Metadata<'static>) -> Interest {
if Self::is_enabled(meta) {
Interest::always()
} else {
Interest::never()
}
}
// Still called when other filters disagree on the callsite's interest.
fn enabled(&self, meta: &Metadata<'_>, _cx: &Context<'_, S>) -> bool {
Self::is_enabled(meta)
}
}
/// Forwards Rust tracing events to Gecko logging.
pub struct MozLogLayer;
impl<S: Subscriber> Layer<S> for MozLogLayer {
fn on_event(&self, event: &Event<'_>, _ctx: Context<'_, S>) {
let metadata = event.metadata();
gecko_logger::moz_log(metadata.target(), to_log_level(*metadata.level()), |out| {
event.record(&mut FieldFormatter { out })
});
}
}