fix: handle None state values in skill_toolset after session rewind

Merge #5204

Co-authored-by: Xuan Yang <xygoogle@google.com>
COPYBARA_INTEGRATE_REVIEW=#5204 from enjoykumawat:fix/load-skill-tool-none-guard ad027fc
PiperOrigin-RevId: 900930037

Author: 2 people

src/google/adk/tools/skill_toolset.py

@@ -165,7 +165,7 @@ async def run_async(
     agent_name = tool_context.agent_name
     state_key = f"_adk_activated_skill_{agent_name}"
 
-    activated_skills = list(tool_context.state.get(state_key, []))
+    activated_skills = list(tool_context.state.get(state_key) or [])
     if skill_name not in activated_skills:
       activated_skills.append(skill_name)
       tool_context.state[state_key] = activated_skills
@@ -732,7 +732,6 @@ async def run_async(
           "error_code": "SKILL_NOT_FOUND",
       }
 
-    script = None
     if file_path.startswith("scripts/"):
       script = skill.resources.get_script(file_path[len("scripts/") :])
     else:
@@ -845,7 +844,7 @@ async def _resolve_additional_tools_from_state(
 
     agent_name = readonly_context.agent_name
     state_key = f"_adk_activated_skill_{agent_name}"
-    activated_skills = readonly_context.state.get(state_key, [])
+    activated_skills = readonly_context.state.get(state_key) or []
 
     if not activated_skills:
       return []

tests/unittests/tools/test_skill_toolset.py

@@ -186,6 +186,20 @@ async def test_get_tools(mock_skill1, mock_skill2):
   assert isinstance(tools[3], skill_toolset.RunSkillScriptTool)
 
 
+@pytest.mark.asyncio
+async def test_resolve_additional_tools_from_state_none(mock_skill1):
+  toolset = skill_toolset.SkillToolset([mock_skill1])
+
+  # Mock ReadonlyContext
+  readonly_context = mock.create_autospec(ReadonlyContext, instance=True)
+  readonly_context.agent_name = "test_agent"
+  readonly_context.state.get.return_value = None
+
+  result = await toolset._resolve_additional_tools_from_state(readonly_context)
+
+  assert not result
+
+
 @pytest.mark.asyncio
 async def test_list_skills_tool(
     mock_skill1, mock_skill2, tool_context_instance
@@ -238,6 +252,28 @@ async def test_load_skill_run_async(
   assert result == expected_result
 
 
+@pytest.mark.asyncio
+async def test_load_skill_run_async_state_none(
+    mock_skill1, tool_context_instance
+):
+  toolset = skill_toolset.SkillToolset([mock_skill1])
+  tool = skill_toolset.LoadSkillTool(toolset)
+
+  # Mock state to return None for the key
+  state_key = "_adk_activated_skill_test_agent"
+  tool_context_instance.state.get.return_value = None
+
+  result = await tool.run_async(
+      args={"skill_name": "skill1"}, tool_context=tool_context_instance
+  )
+
+  assert result["skill_name"] == "skill1"
+  # Verify that it correctly set the list in state
+  tool_context_instance.state.__setitem__.assert_called_with(
+      state_key, ["skill1"]
+  )
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "args, expected_result",