Introduce tracing macros to the preimage crate.

crates/preimage/Cargo.toml

@@ -15,10 +15,10 @@ tokio = { version = "1.32.0", features = ["full"] }
 
 # misc
 anyhow = "1.0.75"
-tracing = "0.1.37"
+tracing = { version = "0.1.37", optional = true }
 
 [dev-dependencies]
 rand = "0.8.5"
 
 [features]
-tracing = []
+tracing = ["dep:tracing"]

crates/preimage/src/hints.rs

@@ -27,10 +27,12 @@ impl Hinter for HintWriter {
         hint_bytes[0..4].copy_from_slice((hint.len() as u32).to_be_bytes().as_ref());
         hint_bytes[4..].copy_from_slice(hint);
 
+        crate::debug!("Sending hint: {:?}", hint_bytes);
         self.tx.send(hint_bytes)?;
 
         let n = self.rx.recv()?;
         if n.len() != 1 {
+            crate::error!("Failed to read hint ack, received response: {:?}", n);
             anyhow::bail!(
                 "Failed to read invalid pre-image hint ack, received response: {:?}",
                 n
@@ -74,6 +76,7 @@ impl HintReader {
         if let Err(e) = router(&payload) {
             // Write back on error to unblock the hint writer.
             self.tx.send(vec![0])?;
+            crate::error!("Failed to handle hint: {:?}", e);
             anyhow::bail!("Failed to handle hint: {:?}", e);
         }
 

crates/preimage/src/lib.rs

@@ -1,6 +1,8 @@
 #![doc = include_str!("../README.md")]
 #![allow(dead_code, unused_variables)]
 
+pub(crate) mod traces;
+
 mod oracle;
 pub use oracle::{OracleClient, OracleServer};
 

crates/preimage/src/traces.rs

@@ -0,0 +1,49 @@
+/// Performs a tracing debug if the `tracing` feature is enabled.
+#[macro_export]
+macro_rules! debug {
+    ($($arg:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::debug!($($arg)*);
+    };
+}
+pub use debug;
+
+/// Performs a tracing info if the `tracing` feature is enabled.
+#[macro_export]
+macro_rules! info {
+    ($($arg:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::info!($($arg)*);
+    };
+}
+pub use info;
+
+/// Performs a tracing error if the `tracing` feature is enabled.
+#[macro_export]
+macro_rules! error {
+    ($($arg:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::error!($($arg)*);
+    };
+}
+pub use error;
+
+/// Performs a tracing warn if the `tracing` feature is enabled.
+#[macro_export]
+macro_rules! warn {
+    ($($arg:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::warn!($($arg)*);
+    };
+}
+pub use crate::warn;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_debug() {
+        debug!("test");
+    }
+}