tracing-line-filter

A [tracing] filter for enabling individual [spans] and [events] by line number.

[tracing] is a framework for instrumenting Rust programs to collect scoped, structured, and async-aware diagnostics. The [tracing-subscriber] crate's [EnvFilter] type provides a mechanism for controlling what tracing [spans] and [events] are collected by matching their targets, verbosity levels, and fields. In some cases, though, it can be useful to toggle on or off individual spans or events with a higher level of granularity. Therefore, this crate provides a filtering [Layer] that enables individual spans and events based on their module path/file path and line numbers.

Since the implementation of this filter is rather simple, the source code of this crate is also useful as an example to tracing users who want to implement their own filtering logic.

Usage

First, add this to your Cargo.toml:

toml tracing-line-filter = "0.1"

Examples

Enabling events by line:

```rust use tracinglinefilter::LineFilter; mod somemodule { pub fn dostuff() { tracing::info!("i'm doing stuff"); tracing::debug!("i'm also doing stuff!"); } }

fn main() { use tracing_subscriber::prelude::*;

let mut filter = LineFilter::default();
filter
    .enable_by_mod("my_crate::some_module", 6)
    .enable_by_mod("my_crate", 25)
    .enable_by_mod("my_crate", 27);

tracing_subscriber::registry()
    .with(tracing_subscriber::fmt::layer().pretty())
    .with(filter)
    .init();

tracing::info!("i'm not enabled");
tracing::debug!("i'm enabled!");
some_module::do_stuff();
tracing::trace!("hi!");

} ```

Chaining a [LineFilter] with a tracing_subscriber [EnvFilter]:

```rust use tracinglinefilter::LineFilter; use tracing_subscriber::EnvFilter;

mod somemodule { pub fn dostuff() { tracing::info!("i'm doing stuff"); tracing::debug!("i'm also doing stuff!"); // This won't be enabled, because it's at the TRACE level, and the // EnvFilter only enables up to the DEBUG level. tracing::trace!("doing very verbose stuff"); } }

fn main() { use tracing_subscriber::prelude::*;

let mut filter = LineFilter::default();
filter
    .enable_by_mod("with_env_filter", 30)
    .enable_by_mod("with_env_filter", 33)
    // use an `EnvFilter` that enables DEBUG and lower in `some_module`,
    // and everything at the ERROR level.
    .with_env_filter(EnvFilter::new("error,with_env_filter::some_module=debug"));

tracing_subscriber::registry()
    .with(tracing_subscriber::fmt::layer().pretty())
    .with(filter)
    .init();

tracing::info!("i'm not enabled");
tracing::debug!("i'm enabled!!");
some_module::do_stuff();
tracing::trace!("hi!");

// This will be enabled by the `EnvFilter`.
tracing::error!("an error!");

} ```