feat(agents): restore 1.x agent config wiring for backward compatibility

Change-Id: I1c8b61cf21d5fef8a622b93f55411e1628845097

Author: GWeale

src/google/adk/agents/agent_config.py

@@ -21,6 +21,7 @@
 from pydantic import Discriminator
 from pydantic import RootModel
 from pydantic import Tag
+from typing_extensions import deprecated
 
 from ..features import experimental
 from ..features import FeatureName
@@ -68,6 +69,7 @@ def agent_config_discriminator(v: Any) -> str:
 
 # Use a RootModel to represent the agent directly at the top level.
 # The `discriminator` is applied to the union within the RootModel.
+@deprecated("AgentConfig is deprecated and will be removed in future versions.")
 @experimental(FeatureName.AGENT_CONFIG)
 class AgentConfig(RootModel[ConfigsUnion]):
   """The config for the YAML schema to create an agent."""

src/google/adk/agents/base_agent.py

@@ -35,6 +35,7 @@
 from pydantic import ConfigDict
 from pydantic import Field
 from pydantic import field_validator
+from typing_extensions import deprecated
 from typing_extensions import override
 from typing_extensions import TypeAlias
 
@@ -45,6 +46,7 @@
 from ..telemetry import _instrumentation
 from ..utils.context_utils import Aclosing
 from ..workflow._base_node import BaseNode
+from .base_agent_config import BaseAgentConfig
 from .callback_context import CallbackContext
 from .context import Context
 
@@ -92,6 +94,25 @@ class BaseAgent(BaseNode):
   )
   """The pydantic model config."""
 
+  config_type: ClassVar[type[BaseAgentConfig]] = BaseAgentConfig
+  """The config type for this agent.
+
+  DEPRECATED: This attribute is deprecated and will be removed in a future
+  version, along with the AgentConfig YAML loader.
+
+  Sub-classes should override this to specify their own config type.
+
+  Example:
+
+  ```
+  class MyAgentConfig(BaseAgentConfig):
+    my_field: str = ''
+
+  class MyAgent(BaseAgent):
+    config_type: ClassVar[type[BaseAgentConfig]] = MyAgentConfig
+  ```
+  """
+
   name: str
   """The agent's name.
 
@@ -619,3 +640,93 @@ def __set_parent_agent_for_sub_agents(self) -> BaseAgent:
         )
       sub_agent.parent_agent = self
     return self
+
+  @classmethod
+  @deprecated(
+      'BaseAgent.from_config is deprecated and will be removed in future'
+      ' versions.'
+  )
+  @experimental(FeatureName.AGENT_CONFIG)
+  def from_config(
+      cls: Type[SelfAgent],
+      config: BaseAgentConfig,
+      config_abs_path: str,
+  ) -> SelfAgent:
+    """Creates an agent from a config.
+
+    If sub-classes use a custom agent config, override `_parse_config` to
+    return updated kwargs for the agent constructor.
+
+    Args:
+      config: The config to create the agent from.
+      config_abs_path: The absolute path to the config file that contains the
+        agent 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
+  @experimental(FeatureName.AGENT_CONFIG)
+  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 custom 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
+
+    kwargs: Dict[str, Any] = {
+        'name': config.name,
+        'description': config.description,
+    }
+    if config.sub_agents:
+      sub_agents = []
+      for sub_agent_config in config.sub_agents:
+        sub_agent = resolve_agent_reference(sub_agent_config, config_abs_path)
+        sub_agents.append(sub_agent)
+      kwargs['sub_agents'] = sub_agents
+
+    if config.before_agent_callbacks:
+      kwargs['before_agent_callback'] = resolve_callbacks(
+          config.before_agent_callbacks
+      )
+    if config.after_agent_callbacks:
+      kwargs['after_agent_callback'] = resolve_callbacks(
+          config.after_agent_callbacks
+      )
+
+    # Preserves 1.x AgentConfigMapper behavior: extra YAML fields that match
+    # a constructor parameter pass through automatically.
+    if config.model_extra:
+      for key, value in config.model_extra.items():
+        if key in cls.model_fields and key not in kwargs:
+          kwargs[key] = value
+    return kwargs

src/google/adk/agents/base_agent_config.py

@@ -25,6 +25,7 @@
 from pydantic import BaseModel
 from pydantic import ConfigDict
 from pydantic import Field
+from typing_extensions import deprecated
 
 from ..features import experimental
 from ..features import FeatureName
@@ -34,6 +35,9 @@
 TBaseAgentConfig = TypeVar('TBaseAgentConfig', bound='BaseAgentConfig')
 
 
+@deprecated(
+    'BaseAgentConfig is deprecated and will be removed in future versions.'
+)
 @experimental(FeatureName.AGENT_CONFIG)
 class BaseAgentConfig(BaseModel):
   """The config for the YAML schema of a BaseAgent.

src/google/adk/agents/common_configs.py

@@ -16,8 +16,6 @@
 
 from __future__ import annotations
 
-from typing import Any
-from typing import List
 from typing import Optional
 
 from pydantic import BaseModel
@@ -28,33 +26,18 @@
 from ..features import FeatureName
 
 
-@experimental(FeatureName.AGENT_CONFIG)
-class ArgumentConfig(BaseModel):
-  """An argument passed to a function or a class's constructor."""
-
-  model_config = ConfigDict(extra="forbid")
-
-  name: Optional[str] = None
-  """Optional. The argument name.
-
-  When the argument is for a positional argument, this can be omitted.
-  """
-
-  value: Any
-  """The argument value."""
-
-
 @experimental(FeatureName.AGENT_CONFIG)
 class CodeConfig(BaseModel):
   """Code reference config for a variable, a function, or a class.
 
-  This config is used for configuring callbacks and tools.
+  Only references an object by name. YAML cannot pass constructor args; to
+  use a configured object, build it in Python and reference its FQN here.
   """
 
   model_config = ConfigDict(extra="forbid")
 
   name: str
-  """Required. The name of the variable, function, class, etc. in code.
+  """Required. The fully qualified name of the variable, function, or class.
 
   Examples:
 
@@ -65,22 +48,6 @@ class CodeConfig(BaseModel):
     When used for callbacks, it refers to a function, e.g. `my_library.my_callbacks.my_callback`
   """
 
-  args: Optional[List[ArgumentConfig]] = None
-  """Optional. The arguments for the code when `name` refers to a function or a
-  class's constructor.
-
-  Examples:
-    ```
-    tools
-      - name: AgentTool
-        args:
-          - name: agent
-            value: search_agent.yaml
-          - name: skip_summarization
-            value: True
-    ```
-  """
-
 
 @experimental(FeatureName.AGENT_CONFIG)
 class AgentRefConfig(BaseModel):