add err output when server failed to start

src/server.rs

@@ -1,7 +1,7 @@
 use crate::server::utils::{get_free_port, wait_for_port};
 use mktemp::Temp;
 use std::error::Error;
-use std::io::{Cursor, Read};
+use std::io::{self, Cursor, Read};
 use std::process::{Child, Stdio};
 use zip::ZipArchive;
 
@@ -53,7 +53,7 @@ impl EmbeddedServer {
             .arg("-p")
             .arg(port.to_string())
             .stdout(Stdio::null())
-            .stderr(Stdio::null())
+            .stderr(Stdio::piped())
             .spawn()?;
 
         wait_for_port(&mut child, port)?;
@@ -78,7 +78,8 @@ impl Drop for EmbeddedServer {
 }
 
 mod utils {
-    use std::io::ErrorKind;
+    use std::fmt::Write;
+    use std::io::{BufRead, BufReader, ErrorKind};
     use std::process::Child;
     use std::time::Duration;
 
@@ -115,10 +116,24 @@ mod utils {
     fn check_server(child: &mut Child) -> Result<(), std::io::Error> {
         match child.try_wait() {
             Ok(None) => Ok(()), // Continue
-            Ok(Some(status)) => Err(std::io::Error::new(
-                ErrorKind::Other,
-                format!("grammalecte-server exit with {status}"),
-            )),
+            Ok(Some(status)) => {
+                let mut err_msg = format!("grammalecte-server exit with `{status}`");
+
+                if let Some(err) = child.stderr.take() {
+                    writeln!(&mut err_msg, " :").unwrap();
+                    let err = BufReader::new(err);
+                    err.lines().for_each(|line| match line {
+                        Ok(line) => {
+                            writeln!(&mut err_msg, "\t{}", line).unwrap();
+                        }
+                        Err(err) => {
+                            writeln!(&mut err_msg, "__{err:?}").unwrap();
+                        }
+                    });
+                };
+
+                Err(std::io::Error::new(ErrorKind::Other, err_msg))
+            }
             Err(err) => Err(std::io::Error::new(
                 ErrorKind::Other,
                 format!("Error append during check grammalecte-server status {err}"),