feat: forward errors to stderr

Author: maximka76667

backend/pkg/logger/trace/trace.go

@@ -69,6 +69,13 @@ func InitTrace(traceLevel string) *os.File {
 	// Human-friendly console writer that prints logs to stdout.
 	consoleWriter := zerolog.ConsoleWriter{Out: os.Stdout}
 
+	// Console writer that prints warn/error/fatal logs to stderr so the
+	// parent process (Electron) can capture them via the stderr pipe.
+	stderrConsoleWriter := &levelFilterWriter{
+		w:        zerolog.ConsoleWriter{Out: os.Stderr},
+		minLevel: zerolog.WarnLevel,
+	}
+
 	// Try to create/open the file for writing logs. On failure, fall back to console only and exit.
 	file, err := loggerbase.CreateFile(traceDir, Trace, traceFile)
 	if err != nil {
@@ -78,8 +85,8 @@ func InitTrace(traceLevel string) *os.File {
 		return nil
 	}
 
-	// Write logs to both the console and the file.
-	multi := zerolog.MultiLevelWriter(consoleWriter, file)
+	// Write logs to stdout, stderr (warn+), and the file.
+	multi := zerolog.MultiLevelWriter(consoleWriter, stderrConsoleWriter, file)
 
 	// Create a new logger that includes timestamps and caller information.
 	trace.Logger = zerolog.New(multi).With().Timestamp().Caller().Logger()
@@ -96,3 +103,24 @@ func InitTrace(traceLevel string) *os.File {
 
 	return file
 }
+
+// levelFilterWriter is a zerolog.LevelWriter that forwards log entries to w
+// only when their level is >= minLevel. This lets us route warn/error/fatal
+// to stderr while keeping info/debug on stdout.
+type levelFilterWriter struct {
+	w        zerolog.ConsoleWriter
+	minLevel zerolog.Level
+}
+
+// Write satisfies the io.Writer interface required by zerolog.LevelWriter.
+// MultiLevelWriter always calls WriteLevel instead.
+func (f *levelFilterWriter) Write(p []byte) (int, error) {
+	return f.w.Write(p)
+}
+
+func (f *levelFilterWriter) WriteLevel(l zerolog.Level, p []byte) (int, error) {
+	if l >= f.minLevel {
+		return f.w.Write(p)
+	}
+	return len(p), nil
+}

electron-app/src/processes/backend.js

@@ -28,9 +28,30 @@ let backendProcess = null;
 // Common log window instance for all backend processes
 let storedLogWindow = null;
 
-// Store error messages (keep last 10 lines to avoid memory issues)
+// Store error messages accumulated from the current process run
 let lastBackendError = null;
 
+const ERROR_HINTS = [
+  {
+    pattern: /bind: The requested address is not valid/,
+    message: "Network address unavailable",
+    advice:
+      "The configured IP address doesn't exist on this machine. Check your network adapter or ADJ.",
+  },
+  {
+    pattern: /failed to start UDP server/,
+    message: "UDP server failed to start",
+    advice: "Another process may already be using this port.",
+  },
+];
+
+function getHint(errorText) {
+  const match = ERROR_HINTS.find(({ pattern }) => pattern.test(errorText));
+  return match
+    ? `${match.message}\n\n${match.advice}\n\n${errorText}`
+    : errorText;
+}
+
 /**
  * Starts the backend process by spawning the backend binary with the user configuration.
  * @returns {void}
@@ -73,6 +94,9 @@ async function startBackend(logWindow = null) {
       cwd: workingDir,
     });
 
+    console.log("[DEBUG] backendProcess.stderr:", backendProcess.stderr);
+    console.log("[DEBUG] backendProcess.stdout:", backendProcess.stdout);
+
     // Log stdout output from backend
     backendProcess.stdout.on("data", (data) => {
       const text = data.toString().trim();
@@ -101,6 +125,7 @@ async function startBackend(logWindow = null) {
     backendProcess.stderr.on("data", (data) => {
       const errorMsg = data.toString().trim();
       logger.backend.error(errorMsg);
+      console.log("[DEBUG stderr chunk]", JSON.stringify(errorMsg));
       lastBackendError = errorMsg;
 
       // Send error message to log window
@@ -129,7 +154,8 @@ async function startBackend(logWindow = null) {
         let errorMessage = `Backend exited with code ${code}`;
 
         if (lastBackendError) {
-          errorMessage += `\n\n${lastBackendError}`;
+          const stripped = lastBackendError.replace(/\x1b\[[0-9;]*m/g, "");
+          errorMessage += `\n\n${getHint(stripped)}`;
         } else {
           errorMessage += "\n\n(No error output captured)";
         }