refactor: Adds a util method to check the enablement of any env variable

PiperOrigin-RevId: 825199260

Author: Jacksunwei

src/google/adk/models/apigee_llm.py

@@ -27,6 +27,7 @@
 from google.genai import types
 from typing_extensions import override
 
+from ..utils.env_utils import is_env_enabled
 from .google_llm import Gemini
 
 if TYPE_CHECKING:
@@ -142,10 +143,7 @@ def _identify_vertexai(model: str) -> bool:
   """Returns True if the model spec starts with apigee/vertex_ai."""
   return not model.startswith('apigee/gemini/') and (
       model.startswith('apigee/vertex_ai/')
-      or os.environ.get(
-          _GOOGLE_GENAI_USE_VERTEXAI_ENV_VARIABLE_NAME, '0'
-      ).lower()
-      in ['true', '1']
+      or is_env_enabled(_GOOGLE_GENAI_USE_VERTEXAI_ENV_VARIABLE_NAME)
   )
 
 

src/google/adk/sessions/vertex_ai_session_service.py

@@ -35,6 +35,7 @@
 from . import _session_util
 from ..events.event import Event
 from ..events.event_actions import EventActions
+from ..utils.env_utils import is_env_enabled
 from .base_session_service import BaseSessionService
 from .base_session_service import GetSessionConfig
 from .base_session_service import ListSessionsResponse
@@ -364,7 +365,7 @@ def _is_vertex_express_mode(
 ) -> bool:
   """Check if Vertex AI and API key are both enabled replacing project and location, meaning the user is using the Vertex Express Mode."""
   return (
-      os.environ.get('GOOGLE_GENAI_USE_VERTEXAI', '0').lower() in ['true', '1']
+      is_env_enabled('GOOGLE_GENAI_USE_VERTEXAI')
       and os.environ.get('GOOGLE_API_KEY', None) is not None
       and project is None
       and location is None

src/google/adk/utils/env_utils.py

@@ -0,0 +1,59 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for environment variable handling.
+
+This module is for ADK internal use only.
+Please do not rely on the implementation details.
+"""
+
+from __future__ import annotations
+
+import os
+
+
+def is_env_enabled(env_var_name: str, default: str = '0') -> bool:
+  """Check if an environment variable is enabled.
+
+  An environment variable is considered enabled if its value (case-insensitive)
+  is 'true' or '1'.
+
+  Args:
+    env_var_name: The name of the environment variable to check.
+    default: The default value to use if the environment variable is not set.
+      Defaults to '0'.
+
+  Returns:
+    True if the environment variable is enabled, False otherwise.
+
+  Examples:
+    >>> os.environ['MY_FLAG'] = 'true'
+    >>> is_env_enabled('MY_FLAG')
+    True
+
+    >>> os.environ['MY_FLAG'] = '1'
+    >>> is_env_enabled('MY_FLAG')
+    True
+
+    >>> os.environ['MY_FLAG'] = 'false'
+    >>> is_env_enabled('MY_FLAG')
+    False
+
+    >>> is_env_enabled('NONEXISTENT_FLAG')
+    False
+
+    >>> is_env_enabled('NONEXISTENT_FLAG', default='1')
+    True
+  """
+  return os.environ.get(env_var_name, default).lower() in ['true', '1']

src/google/adk/utils/variant_utils.py

@@ -21,7 +21,8 @@
 from __future__ import annotations
 
 from enum import Enum
-import os
+
+from .env_utils import is_env_enabled
 
 _GOOGLE_LLM_VARIANT_VERTEX_AI = 'VERTEX_AI'
 _GOOGLE_LLM_VARIANT_GEMINI_API = 'GEMINI_API'
@@ -42,10 +43,6 @@ class GoogleLLMVariant(Enum):
 def get_google_llm_variant() -> GoogleLLMVariant:
   return (
       GoogleLLMVariant.VERTEX_AI
-      if os.environ.get('GOOGLE_GENAI_USE_VERTEXAI', '0').lower()
-      in [
-          'true',
-          '1',
-      ]
+      if is_env_enabled('GOOGLE_GENAI_USE_VERTEXAI')
       else GoogleLLMVariant.GEMINI_API
   )

tests/unittests/utils/test_env_utils.py

@@ -0,0 +1,49 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from google.adk.utils.env_utils import is_env_enabled
+import pytest
+
+
+@pytest.mark.parametrize(
+    'env_value,expected',
+    [
+        ('true', True),
+        ('TRUE', True),
+        ('TrUe', True),
+        ('1', True),
+        ('false', False),
+        ('FALSE', False),
+        ('0', False),
+        ('', False),
+    ],
+)
+def test_is_env_enabled(monkeypatch, env_value, expected):
+  """Test is_env_enabled with various environment variable values."""
+  monkeypatch.setenv('TEST_FLAG', env_value)
+  assert is_env_enabled('TEST_FLAG') is expected
+
+
+@pytest.mark.parametrize(
+    'default,expected',
+    [
+        ('0', False),
+        ('1', True),
+        ('true', True),
+    ],
+)
+def test_is_env_enabled_with_defaults(monkeypatch, default, expected):
+  """Test is_env_enabled when env var is not set with different defaults."""
+  monkeypatch.delenv('TEST_FLAG', raising=False)
+  assert is_env_enabled('TEST_FLAG', default=default) is expected