feat: Support global endpoint natively in Vertex

PiperOrigin-RevId: 720746911

Author: yinghsienwu

google/genai/_api_client.py

@@ -255,7 +255,7 @@ def __init__(
             'Project and location or API key must be set when using the Vertex '
             'AI API.'
         )
-      if self.api_key:
+      if self.api_key or self.location == 'global':
         self._http_options['base_url'] = (
             f'https://aiplatform.googleapis.com/'
         )

google/genai/tests/client/test_client_initialization.py

@@ -593,3 +593,21 @@ def test_vertexai_apikey_combo3(monkeypatch):
   assert client.models._api_client.location == location
   assert "aiplatform" in client._api_client._http_options["base_url"]
   assert isinstance(client.models._api_client, api_client.ApiClient)
+
+
+def test_vertexai_global_endpoint(monkeypatch):
+  # Vertex AI uses global endpoint when location is global.
+  project_id = "fake_project_id"
+  location = "global"
+  monkeypatch.setenv("GOOGLE_CLOUD_PROJECT", project_id)
+  monkeypatch.setenv("GOOGLE_CLOUD_LOCATION", location)
+
+  client = Client(vertexai=True, location=location)
+
+  assert client.models._api_client.vertexai
+  assert client.models._api_client.project == project_id
+  assert client.models._api_client.location == location
+  assert client.models._api_client._http_options["base_url"] == (
+      "https://aiplatform.googleapis.com/"
+  )
+  assert isinstance(client.models._api_client, api_client.ApiClient)