Use string for RunnerError instead of byte vector (#816)

crates/cli/tests/dylib_test.rs

@@ -41,7 +41,7 @@ fn test_dylib_with_error() -> Result<()> {
     let expected_log_output = "Error:1:24 foo error\n    at foo (function.mjs:1:24)\n    at <anonymous> (function.mjs:1:50)\n\n";
     assert_eq!(
         expected_log_output,
-        String::from_utf8(e.downcast_ref::<RunnerError>().unwrap().stderr.clone())?
+        e.downcast_ref::<RunnerError>().unwrap().stderr
     );
 
     Ok(())

crates/cli/tests/integration_test.rs

@@ -190,9 +190,7 @@ fn test_promises(builder: &mut Builder) -> Result<()> {
     let mut runner = builder.input("promise.js").build()?;
     let res = runner.exec(&[]);
     let err = res.err().unwrap().downcast::<RunnerError>().unwrap();
-    assert!(str::from_utf8(&err.stderr)
-        .unwrap()
-        .contains("Pending jobs in the event queue."));
+    assert!(err.stderr.contains("Pending jobs in the event queue."));
 
     Ok(())
 }
@@ -272,7 +270,7 @@ fn test_error_handling(builder: &mut Builder) -> Result<()> {
 
     let expected_log_output = "Error:2:9 error\n    at error (function.mjs:2:9)\n    at <anonymous> (function.mjs:5:1)\n\n";
 
-    assert_eq!(expected_log_output, str::from_utf8(&err.stderr).unwrap());
+    assert_eq!(expected_log_output, err.stderr);
     Ok(())
 }
 

crates/runner/src/lib.rs

@@ -224,7 +224,7 @@ pub struct Runner {
 #[derive(Debug)]
 pub struct RunnerError {
     pub stdout: Vec<u8>,
-    pub stderr: Vec<u8>,
+    pub stderr: String,
     pub err: anyhow::Error,
 }
 
@@ -234,7 +234,7 @@ impl Display for RunnerError {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "error: {:?}, stdout: {:?}, stderr: {:?}",
+            "error: {:?}, stdout: {:?}, stderr: {}",
             self.err, self.stdout, self.stderr
         )
     }
@@ -809,7 +809,7 @@ impl Runner {
             Ok(_) => Ok((output, logs, fuel_consumed)),
             Err(err) => Err(RunnerError {
                 stdout: output,
-                stderr: logs,
+                stderr: String::from_utf8(logs).unwrap(),
                 err,
             }
             .into()),