feat: Skip running a workflow agent if it has no sub-agents

PiperOrigin-RevId: 811528166

tests/unittests/agents/test_sequential_agent.py

@@ -91,6 +91,20 @@ async def test_run_async(request: pytest.FixtureRequest):
   assert events[1].content.parts[0].text == f'Hello, async {agent_2.name}!'
 
 
+@pytest.mark.asyncio
+async def test_run_async_skip_if_no_sub_agent(request: pytest.FixtureRequest):
+  sequential_agent = SequentialAgent(
+      name=f'{request.function.__name__}_test_agent',
+      sub_agents=[],
+  )
+  parent_ctx = await _create_parent_invocation_context(
+      request.function.__name__, sequential_agent
+  )
+  events = [e async for e in sequential_agent.run_async(parent_ctx)]
+
+  assert not events
+
+
 @pytest.mark.asyncio
 async def test_run_live(request: pytest.FixtureRequest):
   agent_1 = _TestingAgent(name=f'{request.function.__name__}_test_agent_1')