refactor(config): Makes BaseAgent.from_config a final method and let sub-class to optionally override _parse_config to update kwargs if needed

This ensures that the pydantic hooks (e.g. model_validators) are triggered correctly.

PiperOrigin-RevId: 791545704

Author: Jacksunwei

src/google/adk/agents/base_agent.py

@@ -504,20 +504,17 @@ def __set_parent_agent_for_sub_agents(self) -> BaseAgent:
       sub_agent.parent_agent = self
     return self
 
+  @final
   @classmethod
-  @working_in_progress('BaseAgent.from_config is not ready for use.')
   def from_config(
       cls: Type[SelfAgent],
       config: BaseAgentConfig,
       config_abs_path: str,
   ) -> SelfAgent:
     """Creates an agent from a config.
 
-    This method converts fields in a config to the corresponding
-    fields in an agent.
-
-    Child classes should re-implement this method to support loading from their
-    custom config types.
+    If sub-classes uses a custom agent config, override `_from_config_kwargs`
+    method to return an updated kwargs for agent construstor.
 
     Args:
       config: The config to create the agent from.
@@ -527,6 +524,40 @@ def from_config(
     Returns:
       The created agent.
     """
+    kwargs = cls.__create_kwargs(config, config_abs_path)
+    kwargs = cls._parse_config(config, config_abs_path, kwargs)
+    return cls(**kwargs)
+
+  @classmethod
+  def _parse_config(
+      cls: Type[SelfAgent],
+      config: BaseAgentConfig,
+      config_abs_path: str,
+      kwargs: Dict[str, Any],
+  ) -> Dict[str, Any]:
+    """Parses the config and returns updated kwargs to construct the agent.
+
+    Sub-classes should override this method to use a custome agent config class.
+
+    Args:
+      config: The config to parse.
+      config_abs_path: The absolute path to the config file that contains the
+        agent config.
+      kwargs: The keyword arguments used for agent constructor.
+
+    Returns:
+      The updated keyword arguments used for agent constructor.
+    """
+    return kwargs
+
+  @classmethod
+  def __create_kwargs(
+      cls,
+      config: BaseAgentConfig,
+      config_abs_path: str,
+  ) -> Dict[str, Any]:
+    """Creates kwargs for the fields of BaseAgent."""
+
     from .config_agent_utils import resolve_agent_reference
     from .config_agent_utils import resolve_callbacks
 
@@ -549,4 +580,4 @@ def from_config(
       kwargs['after_agent_callback'] = resolve_callbacks(
           config.after_agent_callbacks
       )
-    return cls(**kwargs)
+    return kwargs

src/google/adk/agents/llm_agent.py

@@ -17,12 +17,12 @@
 import importlib
 import inspect
 import logging
-import os
 from typing import Any
 from typing import AsyncGenerator
 from typing import Awaitable
 from typing import Callable
 from typing import ClassVar
+from typing import Dict
 from typing import Literal
 from typing import Optional
 from typing import Type
@@ -46,7 +46,6 @@
 from ..models.llm_response import LlmResponse
 from ..models.registry import LLMRegistry
 from ..planners.base_planner import BasePlanner
-from ..tools.agent_tool import AgentTool
 from ..tools.base_tool import BaseTool
 from ..tools.base_tool import ToolConfig
 from ..tools.base_toolset import BaseToolset
@@ -56,7 +55,6 @@
 from .base_agent import BaseAgent
 from .base_agent_config import BaseAgentConfig
 from .callback_context import CallbackContext
-from .common_configs import CodeConfig
 from .invocation_context import InvocationContext
 from .llm_agent_config import LlmAgentConfig
 from .readonly_context import ReadonlyContext
@@ -586,53 +584,55 @@ def _resolve_tools(
 
     return resolved_tools
 
-  @classmethod
   @override
-  @working_in_progress('LlmAgent.from_config is not ready for use.')
-  def from_config(
+  @classmethod
+  def _parse_config(
       cls: Type[LlmAgent],
       config: LlmAgentConfig,
       config_abs_path: str,
-  ) -> LlmAgent:
+      kwargs: Dict[str, Any],
+  ) -> Dict[str, Any]:
     from .config_agent_utils import resolve_callbacks
     from .config_agent_utils import resolve_code_reference
 
-    agent = super().from_config(config, config_abs_path)
     if config.model:
-      agent.model = config.model
+      kwargs['model'] = config.model
     if config.instruction:
-      agent.instruction = config.instruction
+      kwargs['instruction'] = config.instruction
     if config.disallow_transfer_to_parent:
-      agent.disallow_transfer_to_parent = config.disallow_transfer_to_parent
+      kwargs['disallow_transfer_to_parent'] = config.disallow_transfer_to_parent
     if config.disallow_transfer_to_peers:
-      agent.disallow_transfer_to_peers = config.disallow_transfer_to_peers
+      kwargs['disallow_transfer_to_peers'] = config.disallow_transfer_to_peers
     if config.include_contents != 'default':
-      agent.include_contents = config.include_contents
+      kwargs['include_contents'] = config.include_contents
     if config.input_schema:
-      agent.input_schema = resolve_code_reference(config.input_schema)
+      kwargs['input_schema'] = resolve_code_reference(config.input_schema)
     if config.output_schema:
-      agent.output_schema = resolve_code_reference(config.output_schema)
+      kwargs['output_schema'] = resolve_code_reference(config.output_schema)
     if config.output_key:
-      agent.output_key = config.output_key
+      kwargs['output_key'] = config.output_key
     if config.tools:
-      agent.tools = cls._resolve_tools(config.tools, config_abs_path)
+      kwargs['tools'] = cls._resolve_tools(config.tools, config_abs_path)
     if config.before_model_callbacks:
-      agent.before_model_callback = resolve_callbacks(
+      kwargs['before_model_callback'] = resolve_callbacks(
           config.before_model_callbacks
       )
     if config.after_model_callbacks:
-      agent.after_model_callback = resolve_callbacks(
+      kwargs['after_model_callback'] = resolve_callbacks(
           config.after_model_callbacks
       )
     if config.before_tool_callbacks:
-      agent.before_tool_callback = resolve_callbacks(
+      kwargs['before_tool_callback'] = resolve_callbacks(
           config.before_tool_callbacks
       )
     if config.after_tool_callbacks:
-      agent.after_tool_callback = resolve_callbacks(config.after_tool_callbacks)
+      kwargs['after_tool_callback'] = resolve_callbacks(
+          config.after_tool_callbacks
+      )
     if config.generate_content_config:
-      agent.generate_content_config = config.generate_content_config
-    return agent
+      kwargs['generate_content_config'] = config.generate_content_config
+
+    return kwargs
 
 
 Agent: TypeAlias = LlmAgent

src/google/adk/agents/loop_agent.py

@@ -16,8 +16,10 @@
 
 from __future__ import annotations
 
+from typing import Any
 from typing import AsyncGenerator
 from typing import ClassVar
+from typing import Dict
 from typing import Optional
 from typing import Type
 
@@ -74,15 +76,14 @@ async def _run_live_impl(
     raise NotImplementedError('This is not supported yet for LoopAgent.')
     yield  # AsyncGenerator requires having at least one yield statement
 
-  @classmethod
   @override
-  @working_in_progress('LoopAgent.from_config is not ready for use.')
-  def from_config(
-      cls: Type[LoopAgent],
+  @classmethod
+  def _parse_config(
+      cls: type[LoopAgent],
       config: LoopAgentConfig,
       config_abs_path: str,
-  ) -> LoopAgent:
-    agent = super().from_config(config, config_abs_path)
+      kwargs: Dict[str, Any],
+  ) -> Dict[str, Any]:
     if config.max_iterations:
-      agent.max_iterations = config.max_iterations
-    return agent
+      kwargs['max_iterations'] = config.max_iterations
+    return kwargs

src/google/adk/agents/parallel_agent.py

@@ -17,8 +17,10 @@
 from __future__ import annotations
 
 import asyncio
+from typing import Any
 from typing import AsyncGenerator
 from typing import ClassVar
+from typing import Dict
 from typing import Type
 
 from typing_extensions import override
@@ -119,13 +121,3 @@ async def _run_live_impl(
   ) -> AsyncGenerator[Event, None]:
     raise NotImplementedError('This is not supported yet for ParallelAgent.')
     yield  # AsyncGenerator requires having at least one yield statement
-
-  @classmethod
-  @override
-  @working_in_progress('ParallelAgent.from_config is not ready for use.')
-  def from_config(
-      cls: Type[ParallelAgent],
-      config: ParallelAgentConfig,
-      config_abs_path: str,
-  ) -> ParallelAgent:
-    return super().from_config(config, config_abs_path)

src/google/adk/agents/sequential_agent.py

@@ -81,13 +81,3 @@ def task_completed():
     for sub_agent in self.sub_agents:
       async for event in sub_agent.run_live(ctx):
         yield event
-
-  @classmethod
-  @override
-  @working_in_progress('SequentialAgent.from_config is not ready for use.')
-  def from_config(
-      cls: Type[SequentialAgent],
-      config: SequentialAgentConfig,
-      config_abs_path: str,
-  ) -> SequentialAgent:
-    return super().from_config(config, config_abs_path)