feat: Refactor AgentLoader into base class and add InMemory impl alongside existing filesystem impl

PiperOrigin-RevId: 786008518

Author: Poggecci

src/google/adk/cli/cli_eval.py

@@ -27,7 +27,7 @@
 
 from typing_extensions import deprecated
 
-from ..agents import Agent
+from ..agents.llm_agent import Agent
 from ..artifacts.base_artifact_service import BaseArtifactService
 from ..evaluation.base_eval_service import BaseEvalService
 from ..evaluation.base_eval_service import EvaluateConfig

src/google/adk/cli/fast_api.py

@@ -27,7 +27,6 @@
 from typing import Any
 from typing import List
 from typing import Literal
-from typing import Mapping
 from typing import Optional
 
 import click
@@ -407,20 +406,7 @@ def _parse_agent_engine_resource_name(agent_engine_id_or_resource_name):
 
  @app.get("/list-apps")
  def list_apps() -> list[str]:
- base_path = Path.cwd() / agents_dir
- if not base_path.exists():
- raise HTTPException(status_code=404, detail="Path not found")
- if not base_path.is_dir():
- raise HTTPException(status_code=400, detail="Not a directory")
- agent_names = [
- x
- for x in os.listdir(base_path)
- if os.path.isdir(os.path.join(base_path, x))
- and not x.startswith(".")
- and x != "__pycache__"
- ]
- agent_names.sort()
- return agent_names
+ return agent_loader.list_agents()
 
  @app.get("/debug/trace/{event_id}")
  def get_trace_dict(event_id: str) -> Any:
@@ -525,13 +511,6 @@ async def create_session(
 
  return session
 
- def _get_eval_set_file_path(app_name, agents_dir, eval_set_id) -> str:
- return os.path.join(
- agents_dir,
- app_name,
- eval_set_id + _EVAL_SET_FILE_EXTENSION,
- )
-
  @app.post(
  "/apps/{app_name}/eval_sets/{eval_set_id}",
  response_model_exclude_none=True,

src/google/adk/cli/utils/agent_loader.py

@@ -17,20 +17,23 @@
 import importlib
 import logging
 import os
+from pathlib import Path
 import sys
 from typing import Optional
 
 from pydantic import ValidationError
+from typing_extensions import override
 
 from . import envs
 from ...agents import config_agent_utils
 from ...agents.base_agent import BaseAgent
 from ...utils.feature_decorator import working_in_progress
+from .base_agent_loader import BaseAgentLoader
 
 logger = logging.getLogger("google_adk." + __name__)
 
 
-class AgentLoader:
+class AgentLoader(BaseAgentLoader):
  """Centralized agent loading with proper isolation, caching, and .env loading.
  Support loading agents from below folder/file structures:
  a) {agent_name}.agent as a module name:
@@ -188,6 +191,7 @@ def _perform_load(self, agent_name: str) -> BaseAgent:
  " exposed."
  )
 
+ @override
  def load_agent(self, agent_name: str) -> BaseAgent:
  """Load an agent module (with caching & .env) and return its root_agent."""
  if agent_name in self._agent_cache:
@@ -199,6 +203,20 @@ def load_agent(self, agent_name: str) -> BaseAgent:
  self._agent_cache[agent_name] = agent
  return agent
 
+ @override
+ def list_agents(self) -> list[str]:
+ """Lists all agents available in the agent loader (sorted alphabetically)."""
+ base_path = Path.cwd() / self.agents_dir
+ agent_names = [
+ x
+ for x in os.listdir(base_path)
+ if os.path.isdir(os.path.join(base_path, x))
+ and not x.startswith(".")
+ and x != "__pycache__"
+ ]
+ agent_names.sort()
+ return agent_names
+
  def remove_agent_from_cache(self, agent_name: str):
  # Clear module cache for the agent and its submodules
  keys_to_delete = [

src/google/adk/cli/utils/base_agent_loader.py

@@ -0,0 +1,34 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Base class for agent loaders."""
+
+from __future__ import annotations
+
+from abc import ABC
+from abc import abstractmethod
+
+from ...agents.base_agent import BaseAgent
+
+
+class BaseAgentLoader(ABC):
+ """Abstract base class for agent loaders."""
+
+ @abstractmethod
+ def load_agent(self, agent_name: str) -> BaseAgent:
+ """Loads an instance of an agent with the given name."""
+
+ @abstractmethod
+ def list_agents(self) -> list[str]:
+ """Lists all agents available in the agent loader in alphabetical order."""

tests/unittests/cli/test_fast_api.py

@@ -189,6 +189,9 @@ def __init__(self, agents_dir: str):
  def load_agent(self, app_name):
  return root_agent
 
+ def list_agents(self):
+ return ["test_app"]
+
  return MockAgentLoader(".")