| //! This is an example to test the "meta-logging-in-format" fern cargo features. |
| //! |
| //! The example will hang if the feature is disabled, and will produce cohesive |
| //! logs if it's enabled. |
| use std::fmt; |
| |
| use log::{debug, info}; |
| |
| fn main() { |
| fern::Dispatch::new() |
| .chain(std::io::stdout()) |
| .chain(std::io::stderr()) |
| .chain(fern::log_file("hello.txt").unwrap()) |
| .format(move |out, message, record| { |
| out.finish(format_args!("[{}] {}", record.level(), message)) |
| }) |
| .apply() |
| .unwrap(); |
| |
| // in order to actually trigger the situation that deadlocks, we need a custom |
| // Display implementation which performs logging: |
| struct Thing<'a>(&'a str); |
| |
| impl<'a> fmt::Display for Thing<'a> { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| debug!("formatting Thing wrapping ({})", self.0); |
| f.write_str(self.0) |
| } |
| } |
| |
| info!("I'm logging {}!", Thing("aha")); |
| } |
