fix: search subdirectories for mix.exs to prevent Expert deadlock in monorepos (#1444)

CHANGELOG.md

@@ -25,6 +25,7 @@ Status of the `main` branch. Changes prior to the next official version change w
     - `get_diagnostics_for_symbol`: Retrieves diagnostics pertaining to a specific symbol
 
 * Language Servers:
+  - Elixir (`elixir-tools/next-ls`): Fix deadlock in monorepo projects where `mix.exs` lives in a subdirectory. The server now searches immediate subdirectories when no `mix.exs` is found at the repository root. #1444
   - Java (`eclipse.jdt.ls`): Add upstream JDTLS mode for offline / restricted-network use. Setting both `jdtls_path` and `lombok_path` in `ls_specific_settings.java` makes Serena use an existing upstream JDTLS installation (e.g. `brew install jdtls`) and the system JDK 21+, skipping the ~500 MB vscode-java VSIX, Gradle, and IntelliCode downloads. New related setting `java_home` lets the user override the JDK used to launch JDTLS. Default behavior unchanged — the JDTLS workspace hash is preserved bit-for-bit for users on the default route, so existing project caches are reused without a one-time reindex; the launcher path is mixed into the hash only when `jdtls_path` is set, isolating upstream installations from the default workspace. #1415
 
 # v1.2.0 (2026-04-27)

src/solidlsp/language_servers/elixir_tools/elixir_tools.py

@@ -225,6 +225,36 @@ class ElixirTools(SolidLanguageServer):
     def _normalize_symbol_name(self, symbol: RawDocumentSymbol, relative_file_path: str) -> str:
         return symbol["name"].removeprefix("defp ").removeprefix("def ").split("(", 1)[0].strip()
 
+    def _find_mix_exs(self) -> str | None:
+        """
+        Find mix.exs in the repository.
+
+        Checks {repository_root_path}/mix.exs first (standard layout), then scans
+        immediate subdirectories for mix.exs (monorepo layout, e.g. server/mix.exs).
+        Returns the absolute path to the first match found, or None if not found.
+
+        Note: subdirectory iteration order depends on the filesystem (os.listdir).
+        In practice this is fine — monorepos typically have one Elixir app.
+        """
+        # Check root first
+        root_mix_exs = os.path.join(self.repository_root_path, "mix.exs")
+        if os.path.exists(root_mix_exs):
+            return root_mix_exs
+
+        # Search immediate subdirectories
+        try:
+            for entry in os.listdir(self.repository_root_path):
+                subdir_path = os.path.join(self.repository_root_path, entry)
+                if os.path.isdir(subdir_path):
+                    subdir_mix_exs = os.path.join(subdir_path, "mix.exs")
+                    if os.path.exists(subdir_mix_exs):
+                        log.info(f"Found mix.exs in subdirectory: {entry}/mix.exs")
+                        return subdir_mix_exs
+        except OSError as e:
+            log.warning(f"Error scanning for mix.exs in subdirectories: {e}")
+
+        return None
+
     @staticmethod
     def _get_initialize_params(repository_absolute_path: str) -> InitializeParams:
         """
@@ -364,10 +394,11 @@ class ElixirTools(SolidLanguageServer):
         # Without it Expert sits idle and never emits the $/progress signals we wait for,
         # causing a deadlock. Opening mix.exs is the minimal trigger; we close it again
         # once the server is ready so it does not linger in the open-file set.
-        mix_exs_path = os.path.join(self.repository_root_path, "mix.exs")
-        mix_exs_uri = pathlib.Path(mix_exs_path).as_uri() if os.path.exists(mix_exs_path) else None
+        mix_exs_path = self._find_mix_exs()
+        mix_exs_uri: str | None = None
 
-        if mix_exs_uri is not None:
+        if mix_exs_path is not None:
+            mix_exs_uri = pathlib.Path(mix_exs_path).as_uri()
             with open(mix_exs_path, encoding="utf-8") as f:
                 mix_exs_content = f.read()
             self.server.notify.did_open_text_document(

test/solidlsp/elixir/test_elixir_startup.py

@@ -1,104 +0,0 @@
-"""Unit tests for Elixir Expert language server startup behavior."""
-
-import threading
-from unittest.mock import MagicMock
-
-from solidlsp.language_servers.elixir_tools.elixir_tools import ElixirTools
-
-
-def _make_elixir_tools(tmp_path):
-    language_server = object.__new__(ElixirTools)
-    language_server.repository_root_path = str(tmp_path)
-    language_server.server_ready = threading.Event()
-    language_server.request_id = 0
-    return language_server
-
-
-def _make_mock_server():
-    server = MagicMock()
-    server.send.initialize.return_value = {"capabilities": {"textDocumentSync": {}}}
-    return server
-
-
-class TestElixirToolsStartup:
-    """Tests for ElixirTools._start_server() startup behavior — the Expert deadlock fix."""
-
-    def test_sends_did_open_for_mix_exs_after_initialized(self, tmp_path):
-        """Expert blocks waiting for a didOpen notification to trigger its build pipeline."""
-        (tmp_path / "mix.exs").write_text("defmodule App.MixProject do\n  use Mix.Project\nend\n", encoding="utf-8")
-
-        language_server = _make_elixir_tools(tmp_path)
-        server = _make_mock_server()
-        language_server.server = server
-        language_server.server_ready.set()
-
-        language_server._start_server()
-
-        calls = server.notify.did_open_text_document.call_args_list
-        assert len(calls) == 1, f"Expected one didOpen notification for mix.exs, got {len(calls)}"
-        text_doc = calls[0][0][0]["textDocument"]
-        assert text_doc["uri"].endswith("mix.exs"), f"Expected mix.exs URI, got {text_doc['uri']}"
-        assert text_doc["languageId"] == "elixir"
-
-    def test_did_open_contains_mix_exs_content(self, tmp_path):
-        """The didOpen notification must include the file content so Expert can parse it."""
-        content = "defmodule App.MixProject do\n  use Mix.Project\nend\n"
-        (tmp_path / "mix.exs").write_text(content, encoding="utf-8")
-
-        language_server = _make_elixir_tools(tmp_path)
-        server = _make_mock_server()
-        language_server.server = server
-        language_server.server_ready.set()
-
-        language_server._start_server()
-
-        calls = server.notify.did_open_text_document.call_args_list
-        assert len(calls) == 1
-        text_doc = calls[0][0][0]["textDocument"]
-        assert text_doc["text"] == content
-
-    def test_closes_mix_exs_after_server_ready(self, tmp_path):
-        """mix.exs is closed after Expert signals readiness so it does not linger open."""
-        (tmp_path / "mix.exs").write_text("defmodule App.MixProject do\n  use Mix.Project\nend\n", encoding="utf-8")
-
-        language_server = _make_elixir_tools(tmp_path)
-        server = _make_mock_server()
-        language_server.server = server
-        language_server.server_ready.set()
-
-        language_server._start_server()
-
-        close_calls = server.notify.did_close_text_document.call_args_list
-        assert len(close_calls) == 1, f"Expected one didClose for mix.exs, got {len(close_calls)}"
-        text_doc = close_calls[0][0][0]["textDocument"]
-        assert text_doc["uri"].endswith("mix.exs"), f"Expected mix.exs URI, got {text_doc['uri']}"
-
-    def test_startup_event_order_initialized_then_didopen_then_didclose(self, tmp_path):
-        """Initialized → didOpen(mix.exs) → [ready] → didClose(mix.exs) is the required sequence."""
-        (tmp_path / "mix.exs").write_text("defmodule App.MixProject do\n  use Mix.Project\nend\n", encoding="utf-8")
-
-        events: list[str] = []
-
-        language_server = _make_elixir_tools(tmp_path)
-        server = _make_mock_server()
-        language_server.server = server
-        language_server.server_ready.set()
-
-        server.notify.initialized.side_effect = lambda *_: events.append("initialized")
-        server.notify.did_open_text_document.side_effect = lambda *_: events.append("didOpen")
-        server.notify.did_close_text_document.side_effect = lambda *_: events.append("didClose")
-
-        language_server._start_server()
-
-        assert events == ["initialized", "didOpen", "didClose"], f"Unexpected startup event order: {events}"
-
-    def test_no_crash_when_mix_exs_missing(self, tmp_path):
-        """_start_server must not crash if mix.exs is absent (non-standard project layout)."""
-        language_server = _make_elixir_tools(tmp_path)
-        server = _make_mock_server()
-        language_server.server = server
-        language_server.server_ready.set()
-
-        language_server._start_server()
-
-        server.notify.did_open_text_document.assert_not_called()