feat: modularize fast_api.py to allow simpler construction of API Server

PiperOrigin-RevId: 786467758

src/google/adk/cli/agent_graph.py

@@ -19,11 +19,11 @@ from typing import Union
 
 import graphviz
 
-from ..agents import BaseAgent
-from ..agents import LoopAgent
-from ..agents import ParallelAgent
-from ..agents import SequentialAgent
+from ..agents.base_agent import BaseAgent
 from ..agents.llm_agent import LlmAgent
+from ..agents.loop_agent import LoopAgent
+from ..agents.parallel_agent import ParallelAgent
+from ..agents.sequential_agent import SequentialAgent
 from ..tools.agent_tool import AgentTool
 from ..tools.base_tool import BaseTool
 from ..tools.function_tool import FunctionTool

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

@@ -18,32 +18,8 @@ from typing import Optional
 
 from ...agents.base_agent import BaseAgent
 from ...agents.llm_agent import LlmAgent
+from .state import create_empty_state
 
 __all__ = [
     'create_empty_state',
 ]
-
-
-def _create_empty_state(agent: BaseAgent, all_state: dict[str, Any]):
-  for sub_agent in agent.sub_agents:
-    _create_empty_state(sub_agent, all_state)
-
-  if (
-      isinstance(agent, LlmAgent)
-      and agent.instruction
-      and isinstance(agent.instruction, str)
-  ):
-    for key in re.findall(r'{([\w]+)}', agent.instruction):
-      all_state[key] = ''
-
-
-def create_empty_state(
-    agent: BaseAgent, initialized_states: Optional[dict[str, Any]] = None
-) -> dict[str, Any]:
-  """Creates empty str for non-initialized states."""
-  non_initialized_states = {}
-  _create_empty_state(agent, non_initialized_states)
-  for key in initialized_states or {}:
-    if key in non_initialized_states:
-      del non_initialized_states[key]
-  return non_initialized_states

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

@@ -0,0 +1,45 @@
+# 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.
+"""File system event handler for agent changes to trigger hot reload for agents."""
+
+from __future__ import annotations
+
+import logging
+
+from watchdog.events import FileSystemEventHandler
+
+from .agent_loader import AgentLoader
+from .shared_value import SharedValue
+
+logger = logging.getLogger("google_adk." + __name__)
+
+
+class AgentChangeEventHandler(FileSystemEventHandler):
+
+  def __init__(
+      self,
+      agent_loader: AgentLoader,
+      runners_to_clean: set[str],
+      current_app_name_ref: SharedValue[str],
+  ):
+    self.agent_loader = agent_loader
+    self.runners_to_clean = runners_to_clean
+    self.current_app_name_ref = current_app_name_ref
+
+  def on_modified(self, event):
+    if not (event.src_path.endswith(".py") or event.src_path.endswith(".yaml")):
+      return
+    logger.info("Change detected in agents directory: %s", event.src_path)
+    self.agent_loader.remove_agent_from_cache(self.current_app_name_ref.value)
+    self.runners_to_clean.add(self.current_app_name_ref.value)

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

@@ -0,0 +1,30 @@
+# 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.
+from __future__ import annotations
+
+from typing import Generic
+from typing import TypeVar
+
+import pydantic
+
+T = TypeVar("T")
+
+
+class SharedValue(pydantic.BaseModel, Generic[T]):
+  """Simple wrapper around a value to allow modifying it from callbacks."""
+
+  model_config = pydantic.ConfigDict(
+      arbitrary_types_allowed=True,
+  )
+  value: T

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

@@ -0,0 +1,47 @@
+# 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.
+
+from __future__ import annotations
+
+import re
+from typing import Any
+from typing import Optional
+
+from ...agents.base_agent import BaseAgent
+from ...agents.llm_agent import LlmAgent
+
+
+def _create_empty_state(agent: BaseAgent, all_state: dict[str, Any]):
+  for sub_agent in agent.sub_agents:
+    _create_empty_state(sub_agent, all_state)
+
+  if (
+      isinstance(agent, LlmAgent)
+      and agent.instruction
+      and isinstance(agent.instruction, str)
+  ):
+    for key in re.findall(r'{([\w]+)}', agent.instruction):
+      all_state[key] = ''
+
+
+def create_empty_state(
+    agent: BaseAgent, initialized_states: Optional[dict[str, Any]] = None
+) -> dict[str, Any]:
+  """Creates empty str for non-initialized states."""
+  non_initialized_states = {}
+  _create_empty_state(agent, non_initialized_states)
+  for key in initialized_states or {}:
+    if key in non_initialized_states:
+      del non_initialized_states[key]
+  return non_initialized_states