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

test/solidlsp/test_ls_start_cleanup.py

@@ -0,0 +1,55 @@
+from unittest.mock import MagicMock
+
+import pytest
+
+from solidlsp.ls import SolidLanguageServer
+
+
+class _RaisingLanguageServer(SolidLanguageServer):
+    """Bypasses SolidLanguageServer.__init__ (like DummyLanguageServer in
+    test_rename_didopen.py) so _start_server can be made to raise after the underlying
+    process is already considered running, without spinning up a real language server.
+    """
+
+    def _start_server(self) -> None:
+        raise RuntimeError("simulated: capability assertion failed after initialize()")
+
+    def _create_base_initialize_params(self) -> dict:
+        return {}
+
+
+def _make_server(is_running: bool) -> _RaisingLanguageServer:
+    server = object.__new__(_RaisingLanguageServer)
+    server.ls_id = "python"
+    server.repository_root_path = "/tmp/project"
+    server.server_started = False
+    server.server = MagicMock()
+    server.server.is_running.return_value = is_running
+    return server
+
+
+def test_start_stops_process_when_start_server_raises_after_spawning():
+    """_start_server() spawning the OS process and then raising (e.g. a capability
+    assertion or an initialize() timeout firing post-spawn) must not leak that process:
+    start() itself stops it before re-raising.
+    """
+    server = _make_server(is_running=True)
+
+    with pytest.raises(RuntimeError, match="capability assertion"):
+        server.start()
+
+    server.server.stop.assert_called_once()
+    assert server.server_started is False
+
+
+def test_start_does_not_call_stop_when_start_server_raises_before_spawning():
+    """When _start_server() raises before any process was ever spawned (e.g. the language
+    server binary is missing), there is nothing to stop.
+    """
+    server = _make_server(is_running=False)
+
+    with pytest.raises(RuntimeError, match="capability assertion"):
+        server.start()
+
+    server.server.stop.assert_not_called()
+    assert server.server_started is False