fix: address CodeRabbit review findings

- Close stderr_fd on spawn failure in worker test helpers to prevent fd leak
- Guard send_stateful/send_stateless against empty worker pools to prevent
  out-of-bounds access when stateful_count or stateless_count is zero
- Short-circuit all stateful feature requests when ensure_compiled() returns
  false (document not found) instead of forwarding to worker

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 16bit-ykiko

src/server/master_server.cpp

@@ -625,8 +625,9 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document_position_params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id,
-                                     params.text_document_position_params.text_document.uri);
+            if(!co_await ensure_compiled(path_id,
+                                         params.text_document_position_params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::HoverParams wp;
             wp.path = path;
@@ -655,7 +656,8 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id, params.text_document.uri);
+            if(!co_await ensure_compiled(path_id, params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::SemanticTokensParams wp;
             wp.path = path;
@@ -676,7 +678,8 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id, params.text_document.uri);
+            if(!co_await ensure_compiled(path_id, params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::InlayHintsParams wp;
             wp.path = path;
@@ -697,7 +700,8 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id, params.text_document.uri);
+            if(!co_await ensure_compiled(path_id, params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::FoldingRangeParams wp;
             wp.path = path;
@@ -718,7 +722,8 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id, params.text_document.uri);
+            if(!co_await ensure_compiled(path_id, params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::DocumentSymbolParams wp;
             wp.path = path;
@@ -739,7 +744,8 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id, params.text_document.uri);
+            if(!co_await ensure_compiled(path_id, params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::DocumentLinkParams wp;
             wp.path = path;
@@ -760,7 +766,8 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id, params.text_document.uri);
+            if(!co_await ensure_compiled(path_id, params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::CodeActionParams wp;
             wp.path = path;
@@ -781,8 +788,9 @@ void MasterServer::register_handlers() {
             auto path = uri_to_path(params.text_document_position_params.text_document.uri);
             auto path_id = path_pool.intern(path);
 
-            co_await ensure_compiled(path_id,
-                                     params.text_document_position_params.text_document.uri);
+            if(!co_await ensure_compiled(path_id,
+                                         params.text_document_position_params.text_document.uri))
+                co_return serde_raw{"null"};
 
             worker::GoToDefinitionParams wp;
             wp.path = path;

src/server/worker_pool.h

@@ -90,22 +90,28 @@ template <typename Params>
 RequestResult<Params> WorkerPool::send_stateful(std::uint32_t path_id,
                                                 const Params& params,
                                                 et::ipc::request_options opts) {
+    if(stateful_workers.empty()) {
+        co_return et::outcome_error(et::ipc::Error{"No stateful workers available"});
+    }
     if(!opts.timeout.has_value()) {
         opts.timeout = kWorkerRequestTimeout;
     }
     auto idx = assign_worker(path_id);
-    return stateful_workers[idx].peer->send_request(params, opts);
+    co_return co_await stateful_workers[idx].peer->send_request(params, opts);
 }
 
 template <typename Params>
 RequestResult<Params> WorkerPool::send_stateless(const Params& params,
                                                  et::ipc::request_options opts) {
+    if(stateless_workers.empty()) {
+        co_return et::outcome_error(et::ipc::Error{"No stateless workers available"});
+    }
     if(!opts.timeout.has_value()) {
         opts.timeout = kWorkerRequestTimeout;
     }
     auto idx = next_stateless;
     next_stateless = (next_stateless + 1) % stateless_workers.size();
-    return stateless_workers[idx].peer->send_request(params, opts);
+    co_return co_await stateless_workers[idx].peer->send_request(params, opts);
 }
 
 template <typename Params>

tests/unit/server/worker_test_helpers.h

@@ -112,8 +112,13 @@ struct WorkerHandle {
         };
 
         auto result = et::process::spawn(opts, loop);
-        if(!result)
+        if(!result) {
+#ifndef _WIN32
+            if(stderr_fd >= 0)
+                ::close(stderr_fd);
+#endif
             return false;
+        }
 
         auto& spawn = *result;
         transport = std::make_unique<et::ipc::StreamTransport>(std::move(spawn.stdout_pipe),