Fix error display in tx simulate.

crates/aiken/src/cmd/tx/simulate.rs

@@ -128,15 +128,16 @@ pub fn exec(
                             cpu: accum.cpu + curr.ex_units.steps as i64,
                         });
 
+                eprintln!("\n");
                 println!(
-                    "\n{}",
+                    "{}",
                     serde_json::to_string(&total_budget_used)
                         .map_err(|_| fmt::Error)
                         .into_diagnostic()?
                 );
             }
             Err(err) => {
-                eprintln!("{} {}", "        Error".bold().red(), err.red());
+                eprintln!("{}", display_tx_error(&err));
                 process::exit(1);
             }
         }
@@ -144,3 +145,32 @@ pub fn exec(
 
     Ok(())
 }
+
+fn display_tx_error(err: &tx::error::Error) -> String {
+    let mut msg = format!("{} {}", "        Error".bold().red(), err.red());
+    match err {
+        tx::error::Error::RedeemerError { err, .. } => {
+            msg.push_str(&format!(
+                "\n{}",
+                display_tx_error(err)
+                    .lines()
+                    .skip(1)
+                    .collect::<Vec<_>>()
+                    .join("\n"),
+            ));
+            msg
+        }
+        tx::error::Error::Machine(_, _, traces) => {
+            msg.push_str(
+                traces
+                    .iter()
+                    .map(|s| format!("\n{} {}", "        Trace".bold().yellow(), s.yellow()))
+                    .collect::<Vec<_>>()
+                    .join("")
+                    .as_str(),
+            );
+            msg
+        }
+        _ => msg,
+    }
+}

crates/uplc/src/tx/error.rs

@@ -10,7 +10,7 @@ pub enum Error {
     FlatDecode(#[from] flat_rs::de::Error),
     #[error("{0}")]
     FragmentDecode(#[from] pallas_primitives::Error),
-    #[error("{}\n\n{:#?}\n\n{}", .0, .1, .2.join("\n"))]
+    #[error("{}", .0)]
     Machine(machine::Error, ExBudget, Vec<String>),
     #[error("Native script can't be executed in phase-two")]
     NativeScriptPhaseTwo,