Python: fix(google-ai): skip api_key check when use_vertexai is True (#13607)

## Summary

Fixes #13483

### Motivation and Context

When `use_vertexai=True`, users authenticate via Application Default
Credentials (ADC) and don't need an API key. However, the initialization
check for `api_key` runs unconditionally, blocking Vertex AI users with:

```
ServiceInitializationError: The API key is required when use_vertexai is False.
```

### Description

Guard the `api_key` validation with `not
google_ai_settings.use_vertexai` in all three Google AI service classes:

- `GoogleAIChatCompletion`
- `GoogleAITextCompletion`
- `GoogleAITextEmbedding`

The error message already reads *"when use_vertexai is False"*, so the
condition now matches the intent.

### Before / After

```python
# Before — fails even with use_vertexai=True
GoogleAIChatCompletion(
    use_vertexai=True,
    cloud_project_id="my-project",
    cloud_region="us-central1"
)
# → ServiceInitializationError: The API key is required when use_vertexai is False.

# After — works correctly
GoogleAIChatCompletion(
    use_vertexai=True,
    cloud_project_id="my-project",
    cloud_region="us-central1"
)
# → Initializes successfully, uses ADC for authentication
```

### Contribution Checklist

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
- [x] The code follows the [SK coding
standards](https://github.com/microsoft/semantic-kernel/blob/main/python/README.md)

---------

Co-authored-by: giulio-leone <giulio.leone@users.noreply.github.com>
Co-authored-by: giulio-leone <6887247+giulio-leone@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

.github/workflows/python-integration-tests.yml

@@ -68,6 +68,7 @@ env:
   GOOGLE_AI_EMBEDDING_MODEL_ID: ${{ vars.GOOGLE_AI_EMBEDDING_MODEL_ID }}
   GOOGLE_AI_API_KEY: ${{ secrets.GOOGLE_AI_API_KEY }}
   GOOGLE_AI_CLOUD_PROJECT_ID: ${{ vars.GOOGLE_AI_CLOUD_PROJECT_ID }}
+  GOOGLE_AI_CLOUD_REGION: ${{ vars.GOOGLE_AI_CLOUD_REGION }}
   VERTEX_AI_PROJECT_ID: ${{ vars.VERTEX_AI_PROJECT_ID }}
   VERTEX_AI_GEMINI_MODEL_ID: ${{ vars.VERTEX_AI_GEMINI_MODEL_ID }}
   VERTEX_AI_EMBEDDING_MODEL_ID: ${{ vars.VERTEX_AI_EMBEDDING_MODEL_ID }}

python/semantic_kernel/connectors/ai/google/google_ai/services/google_ai_chat_completion.py

@@ -119,7 +119,9 @@ def __init__(
         if not client:
             if google_ai_settings.use_vertexai and not google_ai_settings.cloud_project_id:
                 raise ServiceInitializationError("Project ID must be provided when use_vertexai is True.")
-            if not google_ai_settings.api_key:
+            if google_ai_settings.use_vertexai and not google_ai_settings.cloud_region:
+                raise ServiceInitializationError("Region must be provided when use_vertexai is True.")
+            if not google_ai_settings.use_vertexai and not google_ai_settings.api_key:
                 raise ServiceInitializationError("The API key is required when use_vertexai is False.")
 
         super().__init__(

python/semantic_kernel/connectors/ai/google/google_ai/services/google_ai_text_completion.py

@@ -90,7 +90,9 @@ def __init__(
         if not client:
             if google_ai_settings.use_vertexai and not google_ai_settings.cloud_project_id:
                 raise ServiceInitializationError("Project ID must be provided when use_vertexai is True.")
-            if not google_ai_settings.api_key:
+            if google_ai_settings.use_vertexai and not google_ai_settings.cloud_region:
+                raise ServiceInitializationError("Region must be provided when use_vertexai is True.")
+            if not google_ai_settings.use_vertexai and not google_ai_settings.api_key:
                 raise ServiceInitializationError("The API key is required when use_vertexai is False.")
 
         super().__init__(

python/semantic_kernel/connectors/ai/google/google_ai/services/google_ai_text_embedding.py

@@ -81,7 +81,9 @@ def __init__(
         if not client:
             if google_ai_settings.use_vertexai and not google_ai_settings.cloud_project_id:
                 raise ServiceInitializationError("Project ID must be provided when use_vertexai is True.")
-            if not google_ai_settings.api_key:
+            if google_ai_settings.use_vertexai and not google_ai_settings.cloud_region:
+                raise ServiceInitializationError("Region must be provided when use_vertexai is True.")
+            if not google_ai_settings.use_vertexai and not google_ai_settings.api_key:
                 raise ServiceInitializationError("The API key is required when use_vertexai is False.")
 
         super().__init__(

python/tests/integration/completions/chat_completion_test_base.py

@@ -61,7 +61,11 @@
 ollama_image_setup: bool = is_service_setup_for_testing(["OLLAMA_CHAT_MODEL_ID_IMAGE"])
 ollama_tool_call_setup: bool = is_service_setup_for_testing(["OLLAMA_CHAT_MODEL_ID_TOOL_CALL"])
 google_ai_setup: bool = is_service_setup_for_testing(["GOOGLE_AI_API_KEY", "GOOGLE_AI_GEMINI_MODEL_ID"])
-vertex_ai_setup: bool = is_service_setup_for_testing(["GOOGLE_AI_CLOUD_PROJECT_ID", "GOOGLE_AI_GEMINI_MODEL_ID"])
+vertex_ai_setup: bool = is_service_setup_for_testing([
+    "GOOGLE_AI_CLOUD_PROJECT_ID",
+    "GOOGLE_AI_GEMINI_MODEL_ID",
+    "GOOGLE_AI_CLOUD_REGION",
+])
 onnx_setup: bool = is_service_setup_for_testing(
     ["ONNX_GEN_AI_CHAT_MODEL_FOLDER"], raise_if_not_set=False
 )  # Tests are optional for ONNX

python/tests/integration/completions/test_text_completion.py

@@ -32,7 +32,11 @@
     "Linux"
 ])
 google_ai_setup: bool = is_service_setup_for_testing(["GOOGLE_AI_API_KEY", "GOOGLE_AI_GEMINI_MODEL_ID"])
-vertex_ai_setup: bool = is_service_setup_for_testing(["GOOGLE_AI_CLOUD_PROJECT_ID", "GOOGLE_AI_GEMINI_MODEL_ID"])
+vertex_ai_setup: bool = is_service_setup_for_testing([
+    "GOOGLE_AI_CLOUD_PROJECT_ID",
+    "GOOGLE_AI_GEMINI_MODEL_ID",
+    "GOOGLE_AI_CLOUD_REGION",
+])
 onnx_setup: bool = is_service_setup_for_testing(
     ["ONNX_GEN_AI_TEXT_MODEL_FOLDER"], raise_if_not_set=False
 )  # Tests are optional for ONNX

python/tests/integration/embeddings/test_embedding_service_base.py

@@ -43,7 +43,11 @@
     ["MISTRALAI_API_KEY", "MISTRALAI_EMBEDDING_MODEL_ID"], raise_if_not_set=False
 )  # We don't have a MistralAI deployment
 google_ai_setup: bool = is_service_setup_for_testing(["GOOGLE_AI_API_KEY", "GOOGLE_AI_EMBEDDING_MODEL_ID"])
-vertex_ai_setup: bool = is_service_setup_for_testing(["GOOGLE_AI_CLOUD_PROJECT_ID", "GOOGLE_AI_EMBEDDING_MODEL_ID"])
+vertex_ai_setup: bool = is_service_setup_for_testing([
+    "GOOGLE_AI_CLOUD_PROJECT_ID",
+    "GOOGLE_AI_EMBEDDING_MODEL_ID",
+    "GOOGLE_AI_CLOUD_REGION",
+])
 ollama_setup: bool = is_service_setup_for_testing(["OLLAMA_EMBEDDING_MODEL_ID"])
 # When testing Bedrock, after logging into AWS CLI this has been set, so we can use it to check if the service is setup
 bedrock_setup: bool = is_service_setup_for_testing(["AWS_DEFAULT_REGION"], raise_if_not_set=False)

python/tests/unit/connectors/ai/google/google_ai/services/test_google_ai_chat_completion.py

@@ -75,6 +75,20 @@ def test_google_ai_chat_completion_init_with_use_vertexai_missing_project_id(goo
         GoogleAIChatCompletion(use_vertexai=True, env_file_path="fake_env_file_path.env")
 
 
+@pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_CLOUD_REGION"]], indirect=True)
+def test_google_ai_chat_completion_init_with_use_vertexai_missing_region(google_ai_unit_test_env) -> None:
+    """Test initialization of GoogleAIChatCompletion with use_vertexai true but missing region"""
+    with pytest.raises(ServiceInitializationError, match="Region must be provided when use_vertexai is True."):
+        GoogleAIChatCompletion(use_vertexai=True, env_file_path="fake_env_file_path.env")
+
+
+@pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_API_KEY"]], indirect=True)
+def test_google_ai_chat_completion_init_with_use_vertexai_no_api_key(google_ai_unit_test_env) -> None:
+    """Test initialization of GoogleAIChatCompletion succeeds with use_vertexai=True and no api_key"""
+    chat_completion = GoogleAIChatCompletion(use_vertexai=True)
+    assert chat_completion.service_settings.use_vertexai is True
+
+
 def test_prompt_execution_settings_class(google_ai_unit_test_env) -> None:
     google_ai_chat_completion = GoogleAIChatCompletion()
     assert google_ai_chat_completion.get_prompt_execution_settings_class() == GoogleAIChatPromptExecutionSettings

python/tests/unit/connectors/ai/google/google_ai/services/test_google_ai_text_completion.py

@@ -67,6 +67,20 @@ def test_google_ai_text_completion_init_with_use_vertexai_missing_project_id(goo
         GoogleAITextCompletion(use_vertexai=True, env_file_path="fake_env_file_path.env")
 
 
+@pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_CLOUD_REGION"]], indirect=True)
+def test_google_ai_text_completion_init_with_use_vertexai_missing_region(google_ai_unit_test_env) -> None:
+    """Test initialization of GoogleAITextCompletion with use_vertexai true but missing region"""
+    with pytest.raises(ServiceInitializationError, match="Region must be provided when use_vertexai is True."):
+        GoogleAITextCompletion(use_vertexai=True, env_file_path="fake_env_file_path.env")
+
+
+@pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_API_KEY"]], indirect=True)
+def test_google_ai_text_completion_init_with_use_vertexai_no_api_key(google_ai_unit_test_env) -> None:
+    """Test initialization of GoogleAITextCompletion succeeds with use_vertexai=True and no api_key"""
+    text_completion = GoogleAITextCompletion(use_vertexai=True)
+    assert text_completion.service_settings.use_vertexai is True
+
+
 def test_prompt_execution_settings_class(google_ai_unit_test_env) -> None:
     google_ai_text_completion = GoogleAITextCompletion()
     assert google_ai_text_completion.get_prompt_execution_settings_class() == GoogleAITextPromptExecutionSettings

python/tests/unit/connectors/ai/google/google_ai/services/test_google_ai_text_embedding.py

@@ -57,7 +57,14 @@ def test_google_ai_text_embedding_init_with_empty_model_id(google_ai_unit_test_e
 def test_google_ai_text_embedding_init_with_empty_api_key(google_ai_unit_test_env) -> None:
     """Test initialization of GoogleAITextEmbedding with an empty api_key"""
     with pytest.raises(ServiceInitializationError, match="The API key is required when use_vertexai is False."):
-        GoogleAITextEmbedding(use_vertexai=True, env_file_path="fake_env_file_path.env")
+        GoogleAITextEmbedding(env_file_path="fake_env_file_path.env")
+
+
+@pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_API_KEY"]], indirect=True)
+def test_google_ai_text_embedding_init_with_use_vertexai_no_api_key(google_ai_unit_test_env) -> None:
+    """Test initialization of GoogleAITextEmbedding succeeds with use_vertexai=True and no api_key"""
+    embedding = GoogleAITextEmbedding(use_vertexai=True)
+    assert embedding.service_settings.use_vertexai is True
 
 
 @pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_CLOUD_PROJECT_ID"]], indirect=True)
@@ -67,6 +74,13 @@ def test_google_ai_text_embedding_init_with_use_vertexai_missing_project_id(goog
         GoogleAITextEmbedding(use_vertexai=True, env_file_path="fake_env_file_path.env")
 
 
+@pytest.mark.parametrize("exclude_list", [["GOOGLE_AI_CLOUD_REGION"]], indirect=True)
+def test_google_ai_text_embedding_init_with_use_vertexai_missing_region(google_ai_unit_test_env) -> None:
+    """Test initialization of GoogleAITextEmbedding with use_vertexai true but missing region"""
+    with pytest.raises(ServiceInitializationError, match="Region must be provided when use_vertexai is True."):
+        GoogleAITextEmbedding(use_vertexai=True, env_file_path="fake_env_file_path.env")
+
+
 def test_prompt_execution_settings_class(google_ai_unit_test_env) -> None:
     google_ai_text_embedding = GoogleAITextEmbedding()
     assert google_ai_text_embedding.get_prompt_execution_settings_class() == GoogleAIEmbeddingPromptExecutionSettings