fix(runtime): guard sync API inside async contexts (#1085)

python/cocoindex/runtime.py

@@ -6,8 +6,9 @@
 import threading
 import asyncio
 import inspect
-from typing import Any, Callable, Coroutine, TypeVar, Awaitable
+import warnings
 
+from typing import Any, Callable, Awaitable, TypeVar, Coroutine
 
 T = TypeVar("T")
 
@@ -24,15 +25,42 @@ def event_loop(self) -> asyncio.AbstractEventLoop:
         """Get the event loop for the cocoindex library."""
         with self._lock:
             if self._event_loop is None:
-                self._event_loop = asyncio.new_event_loop()
-                threading.Thread(
-                    target=self._event_loop.run_forever, daemon=True
-                ).start()
+                loop = asyncio.new_event_loop()
+                self._event_loop = loop
+
+                def _runner(l: asyncio.AbstractEventLoop) -> None:
+                    asyncio.set_event_loop(l)
+                    l.run_forever()
+
+                threading.Thread(target=_runner, args=(loop,), daemon=True).start()
             return self._event_loop
 
     def run(self, coro: Coroutine[Any, Any, T]) -> T:
         """Run a coroutine in the event loop, blocking until it finishes. Return its result."""
-        return asyncio.run_coroutine_threadsafe(coro, self.event_loop).result()
+        try:
+            running_loop = asyncio.get_running_loop()
+        except RuntimeError:
+            running_loop = None
+
+        loop = self.event_loop
+
+        if running_loop is not None:
+            if running_loop is loop:
+                raise RuntimeError(
+                    "CocoIndex sync API was called from inside CocoIndex's async context. "
+                    "Use the async variant of this method instead."
+                )
+            warnings.warn(
+                "CocoIndex sync API was called inside an existing event loop. "
+                "This may block other tasks. Prefer the async method.",
+                RuntimeWarning,
+                stacklevel=2,
+            )
+            fut = asyncio.run_coroutine_threadsafe(coro, loop)
+            return fut.result()
+
+        fut = asyncio.run_coroutine_threadsafe(coro, loop)
+        return fut.result()
 
 
 execution_context = _ExecutionContext()