fix: Fix error message if there is empty string in Gemini message (#164)

* Fix error message if there is empty string in gemini message

* small refactor due to pr comment

aidial_adapter_vertexai/chat/gemini/inputs.py

@@ -89,7 +89,7 @@ async def _message_to_gemini_parts(
             return await processors.process_message(message)
 
         case Role.USER:
-            if content is None:
+            if not content:
                 raise ValidationError("User message content must be present")
             return await processors.process_message(message)
 
@@ -99,7 +99,7 @@ async def _message_to_gemini_parts(
             elif message.tool_calls is not None:
                 return [tool_call_to_part(call) for call in message.tool_calls]
             else:
-                if content is None:
+                if not content:
                     raise ValidationError(
                         "Assistant message content must be present"
                     )

tests/integration_tests/test_chat_completion.py

@@ -22,6 +22,7 @@
     GET_WEATHER_FUNCTION,
     GET_WEATHER_TOOL,
     ChatCompletionResult,
+    ai,
     ai_function,
     ai_tools,
     blue_pic,
@@ -149,6 +150,14 @@ def supports_text_input(deployment: ChatCompletionDeployment) -> bool:
     return deployment != ChatCompletionDeployment.GEMINI_PRO_VISION_1
 
 
+def supports_empty_content(deployment: ChatCompletionDeployment) -> bool:
+    return is_codechat(deployment) or deployment in [
+        ChatCompletionDeployment.CHAT_BISON_1,
+        ChatCompletionDeployment.CHAT_BISON_2,
+        ChatCompletionDeployment.CHAT_BISON_2_32K,
+    ]
+
+
 def is_vision_model(deployment: ChatCompletionDeployment) -> bool:
     return deployment in [
         ChatCompletionDeployment.GEMINI_PRO_VISION_1,
@@ -216,6 +225,40 @@ def test_case(
             expected=for_all_choices(lambda s: "7" in s),
         )
 
+        test_case(
+            name="empty assistant content",
+            messages=[
+                user("hi, what is your name?"),
+                ai(""),
+                user("please come again?"),
+            ],
+            expected=(
+                expected_success
+                if supports_empty_content(deployment)
+                else ExpectedException(
+                    type=UnprocessableEntityError,
+                    message="Assistant message content must be present",
+                    status_code=422,
+                )
+            ),
+        )
+
+        test_case(
+            name="empty user content",
+            messages=[
+                user(""),
+            ],
+            expected=(
+                expected_success
+                if supports_empty_content(deployment)
+                else ExpectedException(
+                    type=UnprocessableEntityError,
+                    message="User message content must be present",
+                    status_code=422,
+                )
+            ),
+        )
+
         test_case(
             name="max tokens 1",
             max_tokens=1,