Traaace

src/main.rs

@@ -1,16 +1,22 @@
 #![deny(clippy::all)]
 #![allow(clippy::blanket_clippy_restriction_lints)]
 #![forbid(
-    clippy::style,
+    // clippy::style,
-    clippy::pedantic,
+    // clippy::pedantic,
     clippy::nursery,
-    clippy::restriction,
+    // clippy::restriction,
     // clippy::cargo
 )]
 
 //! my code and notes from the book "Learn Rust in a Month of Lunches"
 
+use std::error::Error;
+use std::io;
+use tracing::debug;
 use tracing::info;
+use tracing::span;
+use tracing::warn;
+use tracing::Level;
 use tracing_subscriber::fmt::init as init_trace_logger;
 
 /// a doc comment - use `cargo doc --open` to see it?
@@ -30,9 +36,42 @@ fn main() {
     };
 
     {
+        // ch 3
         let me = "meeeeeeeeeeeeeeeeeeeeeeeeeee";
         info!("Hello, {me: <4.12}, meet the real {me}.");
     };
+
+    let span = span!(Level::TRACE, "outer_span");
+    let _enter = span.enter();
+
+    let span = span!(Level::TRACE, "shaving_yaks");
+    let _enter = span.enter();
+
+    info!("shaving yaks");
+
+    let _ = shave(3);
+    let result = shave(4);
+    info!("Shave result: {result:?}");
+}
+
+#[tracing::instrument]
+pub fn shave(yak: usize) -> Result<(), Box<dyn Error + 'static>> {
+    // this creates an event at the DEBUG level with two fields:
+    // - `excitement`, with the key "excitement" and the value "yay!"
+    // - `message`, with the key "message" and the value "hello! I'm gonna shave a yak."
+    //
+    // unlike other fields, `message`'s shorthand initialization is just the string itself.
+    debug!(excitement = "yay!", "hello! I'm gonna shave a yak.");
+    if yak == 3 {
+        warn!("could not locate yak!");
+        // note that this is intended to demonstrate `tracing`'s features, not idiomatic
+        // error handling! in a library or application, you should consider returning
+        // a dedicated `YakError`. libraries like snafu or thiserror make this easy.
+        return Err(io::Error::new(io::ErrorKind::Other, "shaving yak failed!").into());
+    } else {
+        debug!("yak shaved successfully");
+    }
+    Ok(())
 }
 
 // if I were to write a webapp, I would like to avoid postgres