Add regression for failed sloppak websocket load

CHANGELOG.md

@@ -7,6 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- **Failed sloppak loads at the highway websocket no longer crash on a `None` song.**
+  When `sloppak_mod.load_song()` returns `None` (cache corruption, partial
+  extraction, etc.), the handler previously dereferenced `loaded_slop.song`
+  before any guard existed, crashing the connection instead of reporting the
+  failure. The load-failure guard now sits immediately after the load call —
+  the handler sends a `Failed to load sloppak` error and closes the socket
+  instead of continuing into arrangement/stem access with a `None` song.
+
 ### Added
 - **Core reader for source rigs (feedpak 1.18.0).** A pack can declare what a
   MIDI part should sound like by binding a rig; core now reads that binding and

lib/routers/ws_highway.py

@@ -212,6 +212,12 @@ async def _send_keepalives():
                     None,
                     lambda: _ctx.run(sloppak_mod.load_song, filename, dlc, appstate.sloppak_cache_dir),
                 )
+                if loaded_slop is None:
+                    _keepalive_active = False
+                    keepalive_task.cancel()
+                    await websocket.send_json({"error": "Failed to load sloppak"})
+                    await websocket.close()
+                    return
                 song = loaded_slop.song
                 tmp = str(loaded_slop.source_dir)
                 owns_tmp = False

tests/test_highway_ws_failed_sloppak_load.py

@@ -0,0 +1,69 @@
+"""Regression coverage for sloppak load failures in the highway websocket."""
+
+import asyncio
+import importlib
+import sys
+
+import pytest
+
+
+class _CapturingWS:
+    def __init__(self):
+        self.messages = []
+        self.accepted = False
+        self.closed = False
+        self.close_calls = 0
+
+    async def accept(self):
+        self.accepted = True
+
+    async def send_json(self, data):
+        self.messages.append(data)
+
+    async def receive_text(self):
+        await asyncio.sleep(0)
+        return ""
+
+    async def close(self):
+        self.close_calls += 1
+        self.closed = True
+
+
+@pytest.fixture()
+def server(tmp_path, monkeypatch):
+    (tmp_path / "dlc").mkdir()
+    monkeypatch.setenv("CONFIG_DIR", str(tmp_path / "config"))
+    monkeypatch.setenv("DLC_DIR", str(tmp_path / "dlc"))
+    monkeypatch.setenv("FEEDBACK_SKIP_STARTUP_TASKS", "1")
+    sys.modules.pop("server", None)
+    mod = importlib.import_module("server")
+    yield mod, tmp_path / "dlc", tmp_path / "cache"
+    conn = getattr(getattr(mod, "meta_db", None), "conn", None)
+    if conn is not None:
+        getattr(mod, "_join_background_db_threads", lambda: None)()
+        conn.close()
+    sys.modules.pop("server", None)
+
+
+def test_sloppak_loader_returning_none_sends_error_without_touching_stems(
+    server, monkeypatch
+):
+    _server, dlc, cache = server
+    (dlc / "broken.feedpak").mkdir()
+
+    import appstate
+    from routers import ws_highway
+
+    monkeypatch.setattr(appstate, "sloppak_cache_dir", cache)
+    monkeypatch.setattr(ws_highway.sloppak_mod, "load_song", lambda *a, **kw: None)
+
+    ws = _CapturingWS()
+    asyncio.run(ws_highway.highway_ws(ws, "broken.feedpak", arrangement=0))
+
+    assert ws.accepted is True
+    assert ws.closed is True
+    assert ws.close_calls == 1
+    assert ws.messages == [
+        {"type": "loading", "stage": "Extracting..."},
+        {"error": "Failed to load sloppak"},
+    ]