doc & fix: Enhance AgentInstantiationContext with detailed documentat…

…ion and examples for agent instantiation; Fix a but that caused value error when the expected class is not provided in register_factory (#5555)

Resolves #5519

Also spotted and fixed a bug that caused value error from `register_factory`, when the `expected_class` was not provided.

python/packages/autogen-core/src/autogen_core/_agent_instantiation.py

@@ -7,6 +7,81 @@
 
 
 class AgentInstantiationContext:
+    """A static class that provides context for agent instantiation.
+
+    This static class can be used to access the current runtime and agent ID
+    during agent instantiation -- inside the factory function or the agent's
+    class constructor.
+
+    Example:
+
+        Get the current runtime and agent ID inside the factory function and
+        the agent's constructor:
+
+        .. code-block:: python
+
+            import asyncio
+            from dataclasses import dataclass
+
+            from autogen_core import (
+                AgentId,
+                AgentInstantiationContext,
+                MessageContext,
+                RoutedAgent,
+                SingleThreadedAgentRuntime,
+                message_handler,
+            )
+
+
+            @dataclass
+            class TestMessage:
+                content: str
+
+
+            class TestAgent(RoutedAgent):
+                def __init__(self, description: str):
+                    super().__init__(description)
+                    # Get the current runtime -- we don't use it here, but it's available.
+                    _ = AgentInstantiationContext.current_runtime()
+                    # Get the current agent ID.
+                    agent_id = AgentInstantiationContext.current_agent_id()
+                    print(f"Current AgentID from constructor: {agent_id}")
+
+                @message_handler
+                async def handle_test_message(self, message: TestMessage, ctx: MessageContext) -> None:
+                    print(f"Received message: {message.content}")
+
+
+            def test_agent_factory() -> TestAgent:
+                # Get the current runtime -- we don't use it here, but it's available.
+                _ = AgentInstantiationContext.current_runtime()
+                # Get the current agent ID.
+                agent_id = AgentInstantiationContext.current_agent_id()
+                print(f"Current AgentID from factory: {agent_id}")
+                return TestAgent(description="Test agent")
+
+
+            async def main() -> None:
+                # Create a SingleThreadedAgentRuntime instance.
+                runtime = SingleThreadedAgentRuntime()
+
+                # Start the runtime.
+                runtime.start()
+
+                # Register the agent type with a factory function.
+                await runtime.register_factory("test_agent", test_agent_factory)
+
+                # Send a message to the agent. The runtime will instantiate the agent and call the message handler.
+                await runtime.send_message(TestMessage(content="Hello, world!"), AgentId("test_agent", "default"))
+
+                # Stop the runtime.
+                await runtime.stop()
+
+
+            asyncio.run(main())
+
+    """
+
     def __init__(self) -> None:
         raise RuntimeError(
             "AgentInstantiationContext cannot be instantiated. It is a static class that provides context management for agent instantiation."

python/packages/autogen-core/src/autogen_core/_agent_runtime.py

@@ -126,7 +126,7 @@ async def main() -> None:
         Args:
             type (str): The type of agent this factory creates. It is not the same as agent class name. The `type` parameter is used to differentiate between different factory functions rather than agent classes.
             agent_factory (Callable[[], T]): The factory that creates the agent, where T is a concrete Agent type. Inside the factory, use `autogen_core.AgentInstantiationContext` to access variables like the current runtime and agent ID.
-            expected_class (type[T] | None, optional): The expected class of the agent, used for runtime validation of the factory. Defaults to None.
+            expected_class (type[T] | None, optional): The expected class of the agent, used for runtime validation of the factory. Defaults to None. If None, no validation is performed.
         """
         ...
 

python/packages/autogen-core/src/autogen_core/_single_threaded_agent_runtime.py

@@ -676,10 +676,20 @@ def start(self) -> None:
 
         .. code-block:: python
 
+            import asyncio
             from autogen_core import SingleThreadedAgentRuntime
 
-            runtime = SingleThreadedAgentRuntime()
-            runtime.start()
+
+            async def main() -> None:
+                runtime = SingleThreadedAgentRuntime()
+                runtime.start()
+
+                # ... do other things ...
+
+                await runtime.stop()
+
+
+            asyncio.run(main())
 
         """
         if self._run_context is not None:
@@ -765,7 +775,7 @@ async def factory_wrapper() -> T:
             else:
                 agent_instance = maybe_agent_instance
 
-            if type_func_alias(agent_instance) != expected_class:
+            if expected_class is not None and type_func_alias(agent_instance) != expected_class:
                 raise ValueError("Factory registered using the wrong type.")
 
             return agent_instance

python/packages/autogen-core/tests/test_runtime.py

@@ -32,6 +32,31 @@ def tracer_provider() -> TracerProvider:
     return get_test_tracer_provider(test_exporter)
 
 
+@pytest.mark.asyncio
+async def test_agent_type_register_factory() -> None:
+    runtime = SingleThreadedAgentRuntime()
+
+    def agent_factory() -> NoopAgent:
+        id = AgentInstantiationContext.current_agent_id()
+        assert id == AgentId("name1", "default")
+        agent = NoopAgent()
+        assert agent.id == id
+        return agent
+
+    await runtime.register_factory(type=AgentType("name1"), agent_factory=agent_factory, expected_class=NoopAgent)
+
+    with pytest.raises(ValueError):
+        # This should fail because the expected class does not match the actual class.
+        await runtime.register_factory(
+            type=AgentType("name1"),
+            agent_factory=agent_factory,  # type: ignore
+            expected_class=CascadingAgent,
+        )
+
+    # Without expected_class, no error.
+    await runtime.register_factory(type=AgentType("name2"), agent_factory=agent_factory)
+
+
 @pytest.mark.asyncio
 async def test_agent_type_must_be_unique() -> None:
     runtime = SingleThreadedAgentRuntime()

python/packages/autogen-ext/src/autogen_ext/runtimes/grpc/_worker_runtime.py

@@ -723,7 +723,7 @@ async def factory_wrapper() -> T:
             else:
                 agent_instance = maybe_agent_instance
 
-            if type_func_alias(agent_instance) != expected_class:
+            if expected_class is not None and type_func_alias(agent_instance) != expected_class:
                 raise ValueError("Factory registered using the wrong type.")
 
             return agent_instance

python/packages/autogen-ext/tests/test_worker_runtime.py

@@ -52,6 +52,7 @@ async def test_agent_types_must_be_unique_single_worker() -> None:
         )
 
     await worker.register_factory(type=AgentType("name4"), agent_factory=lambda: NoopAgent(), expected_class=NoopAgent)
+    await worker.register_factory(type=AgentType("name5"), agent_factory=lambda: NoopAgent())
 
     await worker.stop()
     await host.stop()