fix: add types to default and verify_token and Request __init__ based on comments in the source code.

google/auth/_default.py

@@ -17,14 +17,22 @@
 Implements application default credentials and project ID detection.
 """
 
+from collections.abc import Sequence
 import io
 import json
 import logging
 import os
+from typing import Optional, TYPE_CHECKING
 import warnings
 
 from google.auth import environment_vars
 from google.auth import exceptions
+
+if TYPE_CHECKING:  # pragma: NO COVER
+    # flake8 raises an error because these lines are not used in the code,
+    # they are only used for type-hinting, hence the F401 pragma. 
+    from google.auth.credentials import Credentials  # noqa: F401
+    from google.auth.transport import Request  # noqa: F401
 import google.auth.transport._http_client
 
 _LOGGER = logging.getLogger(__name__)
@@ -588,7 +596,12 @@ def _apply_quota_project_id(credentials, quota_project_id):
     return credentials
 
 
-def default(scopes=None, request=None, quota_project_id=None, default_scopes=None):
+def default(
+    scopes: Optional[Sequence[str]] = None,
+    request: Optional["google.auth.transport.Request"] = None,
+    quota_project_id: Optional[str] = None,
+    default_scopes: Optional[Sequence[str]] = None,
+) -> tuple["google.auth.credentials.Credentials", Optional[str]]:
     """Gets the default credentials for the current environment.
 
     `Application Default Credentials`_ provides an easy way to obtain

google/auth/transport/requests.py

@@ -21,6 +21,7 @@
 import logging
 import numbers
 import time
+from typing import Optional
 
 try:
     import requests
@@ -137,7 +138,7 @@ class Request(transport.Request):
     .. automethod:: __call__
     """
 
-    def __init__(self, session=None):
+    def __init__(self, session: Optional[requests.Session] = None) -> None:
         if not session:
             session = requests.Session()
 

google/oauth2/id_token.py

@@ -58,10 +58,12 @@
 import http.client as http_client
 import json
 import os
+from typing import Any, Mapping, Union
 
 from google.auth import environment_vars
 from google.auth import exceptions
 from google.auth import jwt
+from google.auth import transport
 
 
 # The URL that provides public certificates for verifying ID tokens issued
@@ -105,12 +107,12 @@ def _fetch_certs(request, certs_url):
 
 
 def verify_token(
-    id_token,
-    request,
-    audience=None,
-    certs_url=_GOOGLE_OAUTH2_CERTS_URL,
-    clock_skew_in_seconds=0,
-):
+    id_token: Union[str, bytes],
+    request: transport.Request,
+    audience: Union[str, list[str], None] = None,
+    certs_url: str = _GOOGLE_OAUTH2_CERTS_URL,
+    clock_skew_in_seconds: int = 0,
+) -> Mapping[str, Any]:
     """Verifies an ID token and returns the decoded token.
 
     Args: