Handle None on the response candidates in Google Generative AI (#142497)

* Added type checking on the candidates list

* Made error message a constant

homeassistant/components/google_generative_ai_conversation/conversation.py

@@ -55,6 +55,10 @@ from .const import (
 # Max number of back and forth with the LLM to generate a response
 MAX_TOOL_ITERATIONS = 10
 
+ERROR_GETTING_RESPONSE = (
+    "Sorry, I had a problem getting a response from Google Generative AI."
+)
+
 
 async def async_setup_entry(
     hass: HomeAssistant,
@@ -429,6 +433,12 @@ class GoogleGenerativeAIConversationEntity(
                     raise HomeAssistantError(
                         f"The message got blocked due to content violations, reason: {chat_response.prompt_feedback.block_reason_message}"
                     )
+                if not chat_response.candidates:
+                    LOGGER.error(
+                        "No candidates found in the response: %s",
+                        chat_response,
+                    )
+                    raise HomeAssistantError(ERROR_GETTING_RESPONSE)
 
             except (
                 APIError,
@@ -452,9 +462,7 @@ class GoogleGenerativeAIConversationEntity(
 
             response_parts = chat_response.candidates[0].content.parts
             if not response_parts:
-                raise HomeAssistantError(
-                    "Sorry, I had a problem getting a response from Google Generative AI."
-                )
+                raise HomeAssistantError(ERROR_GETTING_RESPONSE)
             content = " ".join(
                 [part.text.strip() for part in response_parts if part.text]
             )

tests/components/google_generative_ai_conversation/test_conversation.py

@@ -12,6 +12,7 @@ import voluptuous as vol
 from homeassistant.components import conversation
 from homeassistant.components.conversation import UserContent, async_get_chat_log, trace
 from homeassistant.components.google_generative_ai_conversation.conversation import (
+    ERROR_GETTING_RESPONSE,
     _escape_decode,
     _format_schema,
 )
@@ -492,7 +493,33 @@ async def test_empty_response(
     assert result.response.response_type == intent.IntentResponseType.ERROR, result
     assert result.response.error_code == "unknown", result
     assert result.response.as_dict()["speech"]["plain"]["speech"] == (
-        "Sorry, I had a problem getting a response from Google Generative AI."
+        ERROR_GETTING_RESPONSE
+    )
+
+
+@pytest.mark.usefixtures("mock_init_component")
+async def test_none_response(
+    hass: HomeAssistant, mock_config_entry: MockConfigEntry
+) -> None:
+    """Test empty response."""
+    with patch("google.genai.chats.AsyncChats.create") as mock_create:
+        mock_chat = AsyncMock()
+        mock_create.return_value.send_message = mock_chat
+        chat_response = Mock(prompt_feedback=None)
+        mock_chat.return_value = chat_response
+        chat_response.candidates = None
+        result = await conversation.async_converse(
+            hass,
+            "hello",
+            None,
+            Context(),
+            agent_id="conversation.google_generative_ai_conversation",
+        )
+
+    assert result.response.response_type == intent.IntentResponseType.ERROR, result
+    assert result.response.error_code == "unknown", result
+    assert result.response.as_dict()["speech"]["plain"]["speech"] == (
+        ERROR_GETTING_RESPONSE
     )