feat: Allow user to specify protocol for A2A RPC URL in to_a2a utility

this fixes https://github.com/google/adk-python/issues/2405

PiperOrigin-RevId: 797958771

src/google/adk/a2a/utils/agent_to_a2a.py

@@ -39,11 +39,17 @@ from ...memory.in_memory_memory_service import InMemoryMemoryService
 from ...runners import Runner
 from ...sessions.in_memory_session_service import InMemorySessionService
 from ..executor.a2a_agent_executor import A2aAgentExecutor
+from ..experimental import a2a_experimental
 from .agent_card_builder import AgentCardBuilder
 
 
+@a2a_experimental
 def to_a2a(
-    agent: BaseAgent, *, host: str = "localhost", port: int = 8000
+    agent: BaseAgent,
+    *,
+    host: str = "localhost",
+    port: int = 8000,
+    protocol: str = "http",
 ) -> Starlette:
   """Convert an ADK agent to a A2A Starlette application.
 
@@ -51,13 +57,14 @@ def to_a2a(
       agent: The ADK agent to convert
       host: The host for the A2A RPC URL (default: "localhost")
       port: The port for the A2A RPC URL (default: 8000)
+      protocol: The protocol for the A2A RPC URL (default: "http")
 
   Returns:
       A Starlette application that can be run with uvicorn
 
   Example:
       agent = MyAgent()
-      app = to_a2a(agent, host="localhost", port=8000)
+      app = to_a2a(agent, host="localhost", port=8000, protocol="http")
       # Then run with: uvicorn module:app --host localhost --port 8000
   """
   # Set up ADK logging to ensure logs are visible when using uvicorn directly
@@ -87,7 +94,7 @@ def to_a2a(
   )
 
   # Build agent card
-  rpc_url = f"http://{host}:{port}/"
+  rpc_url = f"{protocol}://{host}:{port}/"
   card_builder = AgentCardBuilder(
       agent=agent,
       rpc_url=rpc_url,

tests/unittests/a2a/utils/test_agent_to_a2a.py

@@ -123,7 +123,7 @@ class TestToA2A:
   @patch("google.adk.a2a.utils.agent_to_a2a.InMemoryTaskStore")
   @patch("google.adk.a2a.utils.agent_to_a2a.AgentCardBuilder")
   @patch("google.adk.a2a.utils.agent_to_a2a.Starlette")
-  def test_to_a2a_custom_host_port(
+  def test_to_a2a_custom_host_port_protocol(
       self,
       mock_starlette_class,
       mock_card_builder_class,
@@ -131,7 +131,7 @@ class TestToA2A:
       mock_request_handler_class,
       mock_agent_executor_class,
   ):
-    """Test to_a2a with custom host and port."""
+    """Test to_a2a with custom host, port, and protocol."""
     # Arrange
     mock_app = Mock(spec=Starlette)
     mock_starlette_class.return_value = mock_app
@@ -145,12 +145,14 @@ class TestToA2A:
     mock_card_builder_class.return_value = mock_card_builder
 
     # Act
-    result = to_a2a(self.mock_agent, host="example.com", port=9000)
+    result = to_a2a(
+        self.mock_agent, host="example.com", port=9000, protocol="https"
+    )
 
     # Assert
     assert result == mock_app
     mock_card_builder_class.assert_called_once_with(
-        agent=self.mock_agent, rpc_url="http://example.com:9000/"
+        agent=self.mock_agent, rpc_url="https://example.com:9000/"
     )
 
   @patch("google.adk.a2a.utils.agent_to_a2a.A2aAgentExecutor")
@@ -704,3 +706,110 @@ class TestToA2A:
     mock_card_builder_class.assert_called_once_with(
         agent=self.mock_agent, rpc_url="http://192.168.1.1:8000/"
     )
+
+  @patch("google.adk.a2a.utils.agent_to_a2a.A2aAgentExecutor")
+  @patch("google.adk.a2a.utils.agent_to_a2a.DefaultRequestHandler")
+  @patch("google.adk.a2a.utils.agent_to_a2a.InMemoryTaskStore")
+  @patch("google.adk.a2a.utils.agent_to_a2a.AgentCardBuilder")
+  @patch("google.adk.a2a.utils.agent_to_a2a.Starlette")
+  def test_to_a2a_with_https_protocol(
+      self,
+      mock_starlette_class,
+      mock_card_builder_class,
+      mock_task_store_class,
+      mock_request_handler_class,
+      mock_agent_executor_class,
+  ):
+    """Test to_a2a with HTTPS protocol."""
+    # Arrange
+    mock_app = Mock(spec=Starlette)
+    mock_starlette_class.return_value = mock_app
+    mock_task_store = Mock(spec=InMemoryTaskStore)
+    mock_task_store_class.return_value = mock_task_store
+    mock_agent_executor = Mock(spec=A2aAgentExecutor)
+    mock_agent_executor_class.return_value = mock_agent_executor
+    mock_request_handler = Mock(spec=DefaultRequestHandler)
+    mock_request_handler_class.return_value = mock_request_handler
+    mock_card_builder = Mock(spec=AgentCardBuilder)
+    mock_card_builder_class.return_value = mock_card_builder
+
+    # Act
+    result = to_a2a(self.mock_agent, protocol="https")
+
+    # Assert
+    assert result == mock_app
+    mock_card_builder_class.assert_called_once_with(
+        agent=self.mock_agent, rpc_url="https://localhost:8000/"
+    )
+
+  @patch("google.adk.a2a.utils.agent_to_a2a.A2aAgentExecutor")
+  @patch("google.adk.a2a.utils.agent_to_a2a.DefaultRequestHandler")
+  @patch("google.adk.a2a.utils.agent_to_a2a.InMemoryTaskStore")
+  @patch("google.adk.a2a.utils.agent_to_a2a.AgentCardBuilder")
+  @patch("google.adk.a2a.utils.agent_to_a2a.Starlette")
+  def test_to_a2a_with_custom_protocol(
+      self,
+      mock_starlette_class,
+      mock_card_builder_class,
+      mock_task_store_class,
+      mock_request_handler_class,
+      mock_agent_executor_class,
+  ):
+    """Test to_a2a with custom protocol."""
+    # Arrange
+    mock_app = Mock(spec=Starlette)
+    mock_starlette_class.return_value = mock_app
+    mock_task_store = Mock(spec=InMemoryTaskStore)
+    mock_task_store_class.return_value = mock_task_store
+    mock_agent_executor = Mock(spec=A2aAgentExecutor)
+    mock_agent_executor_class.return_value = mock_agent_executor
+    mock_request_handler = Mock(spec=DefaultRequestHandler)
+    mock_request_handler_class.return_value = mock_request_handler
+    mock_card_builder = Mock(spec=AgentCardBuilder)
+    mock_card_builder_class.return_value = mock_card_builder
+
+    # Act
+    result = to_a2a(self.mock_agent, protocol="ws")
+
+    # Assert
+    assert result == mock_app
+    mock_card_builder_class.assert_called_once_with(
+        agent=self.mock_agent, rpc_url="ws://localhost:8000/"
+    )
+
+  @patch("google.adk.a2a.utils.agent_to_a2a.A2aAgentExecutor")
+  @patch("google.adk.a2a.utils.agent_to_a2a.DefaultRequestHandler")
+  @patch("google.adk.a2a.utils.agent_to_a2a.InMemoryTaskStore")
+  @patch("google.adk.a2a.utils.agent_to_a2a.AgentCardBuilder")
+  @patch("google.adk.a2a.utils.agent_to_a2a.Starlette")
+  def test_to_a2a_with_all_custom_parameters(
+      self,
+      mock_starlette_class,
+      mock_card_builder_class,
+      mock_task_store_class,
+      mock_request_handler_class,
+      mock_agent_executor_class,
+  ):
+    """Test to_a2a with all custom parameters."""
+    # Arrange
+    mock_app = Mock(spec=Starlette)
+    mock_starlette_class.return_value = mock_app
+    mock_task_store = Mock(spec=InMemoryTaskStore)
+    mock_task_store_class.return_value = mock_task_store
+    mock_agent_executor = Mock(spec=A2aAgentExecutor)
+    mock_agent_executor_class.return_value = mock_agent_executor
+    mock_request_handler = Mock(spec=DefaultRequestHandler)
+    mock_request_handler_class.return_value = mock_request_handler
+    mock_card_builder = Mock(spec=AgentCardBuilder)
+    mock_card_builder_class.return_value = mock_card_builder
+
+    # Act
+    result = to_a2a(
+        self.mock_agent, host="api.example.com", port=443, protocol="https"
+    )
+
+    # Assert
+    assert result == mock_app
+    mock_card_builder_class.assert_called_once_with(
+        agent=self.mock_agent, rpc_url="https://api.example.com:443/"
+    )