Fix corrupt cache detection (lexists) and suppress asyncio GC noise

Two robustness fixes in the HF Spaces startup block:

1. Use os.path.lexists() instead of os.path.exists() to detect corrupt
cache entries. exists() follows symlinks and returns False for broken
symlinks; lexists() checks the path itself — catches regular files,
working symlinks, AND broken symlinks. Also log exactly what was found
(dir / file / symlink / absent) to make future issues diagnosable.
Use os.unlink() which handles both files and symlinks (os.remove()
only handles files).

2. Install sys.unraisablehook to silently drop the Python 3.10 GC bug
(BaseEventLoop.__del__ → "Invalid file descriptor: -1"). This is the
correct Python 3.8+ API for intercepting exceptions raised in __del__
and other un-raisable contexts — cleaner than monkey-patching __del__.

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

image_generator.py

@@ -34,28 +34,45 @@ if not hasattr(torch, "xpu"):
 IS_HF_SPACE = os.environ.get("SPACE_ID") is not None
 if IS_HF_SPACE:
     import spaces
+    import sys, threading, asyncio
+
+    # ── Suppress Python 3.10 asyncio GC bug ──────────────────────────────
+    # BaseEventLoop.__del__ crashes with "Invalid file descriptor: -1" when
+    # an event loop is collected by the GC. sys.unraisablehook is the correct
+    # Python 3.8+ way to intercept these GC-triggered exceptions.
+    _orig_unraisable = sys.unraisablehook
+    def _unraisable_hook(args):
+        if args.exc_type is ValueError and "Invalid file descriptor" in str(args.exc_value):
+            return  # silently drop — harmless Python 3.10 GC bug
+        _orig_unraisable(args)
+    sys.unraisablehook = _unraisable_hook
+
     # Download model files to persistent storage at startup.
     # /data survives rebuilds → only downloads once ever.
     _hf_token  = os.environ.get("HF_TOKEN") or os.environ.get("HUGGING_FACE_HUB_TOKEN")
     _cache_dir = os.environ.get("HF_HUB_CACHE")
     print(f"Pre-caching FLUX.1-schnell → {_cache_dir} (token={'set' if _hf_token else 'NOT SET'})")
     try:
-        # Fix corrupt cache: if the model directory exists as a FILE (not a dir),
-        # remove it so huggingface_hub can create the proper directory structure.
-        import shutil
+        # Diagnose and fix corrupt cache entry.
+        # os.path.exists() follows symlinks — returns False for broken symlinks.
+        # os.path.lexists() checks the path itself — catches files AND broken symlinks.
         _model_cache = os.path.join(_cache_dir, "models--black-forest-labs--FLUX.1-schnell")
-        if os.path.exists(_model_cache) and not os.path.isdir(_model_cache):
-            print(f"⚠️  Removing corrupt cache entry (not a directory): {_model_cache}")
-            os.remove(_model_cache)
+        if os.path.lexists(_model_cache):
+            if os.path.isdir(_model_cache):
+                print(f"Cache dir OK: {_model_cache}")
+            else:
+                kind = "symlink" if os.path.islink(_model_cache) else "file"
+                print(f"⚠️  Removing corrupt cache entry ({kind}): {_model_cache}")
+                os.unlink(_model_cache)  # works for both files and symlinks
+        else:
+            print(f"Cache entry absent — will be created by snapshot_download")
 
         from huggingface_hub import snapshot_download
-        import threading, asyncio
 
         _result = {}
         def _download():
-            # Create and own an explicit event loop for this thread so it can be
-            # closed cleanly before the thread exits — prevents Python 3.10's
-            # BaseEventLoop.__del__ from crashing with "Invalid file descriptor: -1".
+            # Own an explicit event loop so it can be closed cleanly before the
+            # thread exits — prevents the GC from seeing an open loop.
             loop = asyncio.new_event_loop()
             asyncio.set_event_loop(loop)
             try: