Fix: Exceptions raised during LanguageServerManager.start did not stop the language server subprocess if it was already started

start() now catches an exception from _start_server(), stops the process if it is
already running, and re-raises. 

Fixes #1949

src/serena/ls_manager.py

@@ -144,6 +144,9 @@ class LanguageServerManager:
                 language_servers[thread.ls_id] = thread.language_server
 
         # If any server failed to start up, raise an exception and stop all started language servers.
+        # A server whose own thread raised has already stopped its own process, since
+        # SolidLanguageServer.start() cleans up after itself on failure; only the servers that
+        # started successfully (and are therefore absent from `exceptions`) still need stopping.
         # We intentionally fail fast here. The user's intention is to work with all the specified languages,
         # so if any of them is not available, it is better to make symbolic tool calls fail, bringing the issue to the
         # user's attention instead of silently continuing with a subset of the language servers and potentially

src/solidlsp/ls.py

@@ -3179,7 +3179,17 @@ class SolidLanguageServer(ABC):
         """
         log.info(f"Starting language server {self.language_server.ls_id} for {self.language_server.repository_root_path}")
         self.server_started = True
-        self._start_server()
+        try:
+            self._start_server()
+        except Exception:
+            # `_start_server()` may raise after already spawning the underlying process (a
+            # capability assertion or an initialize() timeout firing post-spawn). Stop it here
+            # so a failed start never leaves an orphaned process behind, regardless of caller.
+            if self.is_running():
+                self.stop()
+            else:
+                self.server_started = False
+            raise
         return self
 
     def stop(self, shutdown_timeout: float = 2.0) -> None: