tokio/tokio-net/src/tracing.rs

//! This module provides a small facade that wraps the `tracing` APIs we use, so
//! that when the `tracing` dependency is disabled, `tracing`'s macros expand to
//! no-ops.
//!
//! This means we don't have to put a `#[cfg(feature = "tracing")]` on every
//! individual use of a `tracing` macro.

// The macros in this module may or may not be used depending on the combination
// of feature flags enabled. Rather than feature-flagging each individual macro
// to only be defined when the features that use it are enabled, just allow
// unused macros in some cases.
#![allow(unused_macros)]
#![allow(dead_code)]

#[cfg(not(feature = "tracing"))]
#[derive(Clone, Debug)]
pub(crate) struct Span {}

#[cfg(feature = "tracing")]
macro_rules! trace {
    ($($arg:tt)+) => {
        tracing::trace!($($arg)+)
    };
}

#[cfg(not(feature = "tracing"))]
macro_rules! trace {
    ($($arg:tt)+) => {{}};
}

#[cfg(feature = "tracing")]
macro_rules! debug {
    ($($arg:tt)+) => {
        tracing::debug!($($arg)+)
    };
}

#[cfg(not(feature = "tracing"))]
macro_rules! debug {
    ($($arg:tt)+) => {{}};
}

#[cfg(feature = "tracing")]
macro_rules! error {
    ($($arg:tt)+) => {
        tracing::error!($($arg)+)
    };
}

#[cfg(not(feature = "tracing"))]
macro_rules! error {
    ($($arg:tt)+) => {{}};
}

#[cfg(feature = "tracing")]
macro_rules! trace_span {
    ($($arg:tt)+) => {
        tracing::trace_span!($($arg)+)
    };
}

#[cfg(not(feature = "tracing"))]
macro_rules! trace_span {
    ($($arg:tt)+) => {
        crate::tracing::Span::new()
    };
}

#[cfg(not(feature = "tracing"))]
impl Span {
    pub(crate) fn new() -> Self {
        Span {}
    }

    pub(crate) fn enter(&self) -> Span {
        Span {}
    }
}