fix(watcher): keep working even when imported file has invalid syntax (#9091)

cli/file_watcher.rs

@@ -172,7 +172,7 @@ where
   let mut debounce = Debounce::new();
   // Store previous data. If module resolution fails at some point, the watcher will try to
   // continue watching files using these data.
-  let mut paths;
+  let mut paths = Vec::new();
   let mut module = None;
 
   loop {
@@ -185,7 +185,10 @@ where
         module = Some(module_info);
       }
       ModuleResolutionResult::Fail { source_path, error } => {
+        if paths.is_empty() {
           paths = vec![source_path];
+        }
+
         if module.is_none() {
           eprintln!("{}: {}", colors::red_bold("error"), error);
         }

cli/tests/integration_tests.rs

@@ -1571,6 +1571,21 @@ fn run_watch() {
   assert!(stdout_lines.next().unwrap().contains("42"));
   wait_for_process_finished("Process", &mut stderr_lines);
 
+  // Update the content of the imported file with invalid syntax
+  std::fs::write(&another_file, "syntax error ^^").expect("error writing file");
+  std::thread::sleep(std::time::Duration::from_secs(1));
+  assert!(stderr_lines.next().unwrap().contains("Restarting"));
+  assert!(stderr_lines.next().unwrap().contains("error:"));
+  wait_for_process_finished("Process", &mut stderr_lines);
+
+  // Modify the imported file and make sure that restarting occurs
+  std::fs::write(&another_file, "export const foo = 'modified!';")
+    .expect("error writing file");
+  std::thread::sleep(std::time::Duration::from_secs(1));
+  assert!(stderr_lines.next().unwrap().contains("Restarting"));
+  assert!(stdout_lines.next().unwrap().contains("modified!"));
+  wait_for_process_finished("Process", &mut stderr_lines);
+
   // the watcher process is still alive
   assert!(child.try_wait().unwrap().is_none());