fix: Check environment Vertex AI api key for credential precedence

PiperOrigin-RevId: 822733016

Author: matthew29tang

google/genai/_api_client.py

@@ -599,7 +599,7 @@ def __init__(
  # Handle when to use Vertex AI in express mode (api key).
  # Explicit initializer arguments are already validated above.
  if self.vertexai:
- if credentials:
+ if credentials and env_api_key:
  # Explicit credentials take precedence over implicit api_key.
  logger.info(
  'The user provided Google Cloud credentials will take precedence'

google/genai/tests/client/test_client_initialization.py

@@ -417,6 +417,25 @@ def test_invalid_vertexai_constructor3(monkeypatch):
  Client(vertexai=True, project=project_id)
 
 
+def test_vertexai_explicit_credentials(monkeypatch):
+ creds = credentials.AnonymousCredentials()
+ monkeypatch.setenv("GOOGLE_CLOUD_PROJECT", "fake_project_id")
+ monkeypatch.setenv("GOOGLE_CLOUD_LOCATION", "fake-location")
+ monkeypatch.setenv("GOOGLE_API_KEY", "env_api_key")
+
+ client = Client(
+ vertexai=True,
+ credentials=creds
+ )
+
+ assert client.models._api_client.vertexai
+ assert client.models._api_client.project
+ assert client.models._api_client.location
+ assert not client.models._api_client.api_key
+ assert client.models._api_client._credentials is creds
+ assert isinstance(client.models._api_client, api_client.BaseApiClient)
+
+
 def test_vertexai_explicit_arg_precedence1(monkeypatch):
  project_id = "constructor_project_id"
  location = "constructor-location"