fix(arch-043,arch-052): deterministic system tenant lookup; async-safe file metadata

app/core/storage.py

@@ -501,11 +501,38 @@ async def save_with_metadata(
     }
 
 
+async def get_file_metadata_async(path: str) -> dict[str, Any]:
+    """Awaitable variant of :func:`get_file_metadata` (ARCH-052).
+
+    Safe to call from inside a running event loop — never creates a
+    nested one. For local storage this is plain filesystem access; for
+    S3 and other async backends the backend's ``exists()`` is awaited.
+    """
+    backend = get_storage_backend()
+    if isinstance(backend, LocalStorage):
+        full_path = backend._full_path(path)
+        if not os.path.exists(full_path):
+            return {"size": None, "modified": None, "exists": False}
+        stat = os.stat(full_path)
+        return {
+            "size": stat.st_size,
+            "modified": stat.st_mtime,
+            "exists": True,
+        }
+    # S3 or other async backends — await the backend directly
+    if not await backend.exists(path):
+        return {"size": None, "modified": None, "exists": False}
+    return {"size": None, "modified": None, "exists": True}
+
+
 def get_file_metadata(path: str) -> dict[str, Any]:
     """Read metadata of a stored file without loading its content.
 
-    Works with the *local* storage backend.  For S3, use the S3 client
-    ``stat_object`` API directly.
+    Works with the *local* storage backend without touching the event
+    loop.  For S3 and other async-only backends this drives the check
+    through ``asyncio.run``; calling it from inside a running event loop
+    raises ``RuntimeError`` — use :func:`get_file_metadata_async` there
+    instead (ARCH-052).
 
     Parameters
     ----------
@@ -530,14 +557,15 @@ def get_file_metadata(path: str) -> dict[str, Any]:
             "modified": stat.st_mtime,
             "exists": True,
         }
-    # S3 or other backends — fall back to exists() check
-    import asyncio as _asyncio
-
-    loop = _asyncio.new_event_loop()
+    # Async-only backend outside a running loop is fine; inside one we
+    # must never build a nested event loop.
     try:
-        exists = loop.run_until_complete(backend.exists(path))
-        if not exists:
-            return {"size": None, "modified": None, "exists": False}
-        return {"size": None, "modified": None, "exists": True}
-    finally:
-        loop.close()
+        asyncio.get_running_loop()
+    except RuntimeError:
+        pass
+    else:
+        raise RuntimeError(
+            "get_file_metadata() cannot be used with async storage backends "
+            "inside a running event loop — use get_file_metadata_async()"
+        )
+    return asyncio.run(get_file_metadata_async(path))