fix(worker): event loop should run until yield

cadence/_internal/workflow/deterministic_event_loop.py

@@ -27,6 +27,16 @@ def __init__(self):
         self._stopping = False
         self._closed = False
 
+    def run_until_yield(self):
+        """Run until stop() is called."""
+        self._run_forever_setup()
+        try:
+            while self._ready:
+                self._run_once()
+        finally:
+            self._run_forever_cleanup()
+
+    # Event Loop APIs
     def call_soon(
         self,
         callback: Callable[[Unpack[_Ts]], object],

cadence/_internal/workflow/workflow_engine.py

@@ -225,10 +225,7 @@ def _execute_workflow_once(
                     self._workflow_instance.run(workflow_input)
                 )
 
-                # signal the loop to stop after the first run
-                self._loop.stop()
-                # this starts the loop and runs once then stops with cleanup
-                self._loop.run_forever()
+                self._loop.run_until_yield()
 
         except Exception as e:
             logger.error(

tests/cadence/_internal/workflow/test_deterministic_event_loop.py

@@ -76,3 +76,17 @@ def test_create_task(self):
         size = 10000
         results = self.loop.run_until_complete(coro_await_task(size))
         assert results == list(range(size))
+
+    def test_run_once(self):
+        # run once won't clear the read queue
+        self.loop.create_task(coro_await_task(10))
+        self.loop.stop()
+        self.loop.run_forever()
+        assert len(self.loop._ready) == 10
+
+    def test_run_until_yield(self):
+        # run until yield will clear the read queue
+        task = self.loop.create_task(coro_await_task(3))
+        self.loop.run_until_yield()
+        assert len(self.loop._ready) == 0
+        assert task.done() is True