test: add lazy imports fallback and tests for PEP 810

Author: hebaalazzeh

packages/google-auth/google/auth/transport/__init__.py

@@ -24,6 +24,12 @@
 for the return value of :class:`Request`.
 """
 
+# PEP 0810: Explicit Lazy Imports
+# Python 3.15+ natively intercepts and defers these imports.
+# Developers can disable this behavior and force eager imports.
+# For more information, see:
+# https://docs.python.org/3.15/library/sys.html#sys.set_lazy_imports_filter
+# Older Python versions safely ignore this variable.
 __lazy_modules__ = {
     "google.auth.transport.aiohttp_requests",
     "google.auth.transport._custom_tls_signer",
@@ -114,3 +120,12 @@ def __call__(
         # pylint: disable=redundant-returns-doc, missing-raises-doc
         # (pylint doesn't play well with abstract docstrings.)
         raise NotImplementedError("__call__ must be implemented.")
+
+import sys
+if sys.version_info < (3, 15):
+    import importlib
+    for _lazy_mod in __lazy_modules__:
+        try:
+            importlib.import_module(_lazy_mod)
+        except ImportError:
+            pass

packages/google-auth/tests/transport/test_lazy_imports.py

@@ -0,0 +1,43 @@
+import sys
+import pytest
+
+# List of modules we expect to be lazy
+LAZY_MODULES = [
+    "google.auth.transport.requests",
+    "google.auth.transport.urllib3",
+    "google.auth.transport.grpc",
+]
+
+def clean_sys_modules():
+    """Helper to ensure we start with a clean slate for import testing."""
+    for mod in LAZY_MODULES:
+        sys.modules.pop(mod, None)
+
+@pytest.mark.skipif(sys.version_info < (3, 15), reason="PEP 810 requires Python 3.15+")
+def test_lazy_imports_on_python_315():
+    clean_sys_modules()
+    
+    # 1. Import the transport package
+    import google.auth.transport
+    
+    # 2. Assert that none of the lazy modules have been eagerly loaded into sys.modules
+    for mod in LAZY_MODULES:
+        assert mod not in sys.modules
+        
+    # 3. Access an attribute to trigger reification
+    from google.auth.transport import requests
+    _ = requests.__name__  # Trigger first-use reification
+    
+    # 4. Assert that the module has now been reified and loaded
+    assert "google.auth.transport.requests" in sys.modules
+
+
+@pytest.mark.skipif(sys.version_info >= (3, 15), reason="Testing fallback behavior on < 3.15")
+def test_fallback_eager_imports_pre_315():
+    clean_sys_modules()
+    
+    # On older Python, __lazy_modules__ is safely ignored, meaning they should eager-load
+    import google.auth.transport
+    
+    for mod in LAZY_MODULES:
+        assert mod in sys.modules