REQ: Add type parameter to act as hint for typing.

zerver/lib/request.py

@@ -14,7 +14,7 @@
 
 from django.http import HttpRequest, HttpResponse
 
-from typing import Any, Callable
+from typing import Any, Callable, Type
 
 class RequestVariableMissingError(JsonableError):
     code = ErrorCode.REQUEST_VARIABLE_MISSING
@@ -50,7 +50,7 @@ class _NotSpecified:
 
     def __init__(self, whence: str=None, *, converter: Callable[[Any], Any]=None,
                  default: Any=NotSpecified, validator: Callable[[Any], Any]=None,
-                 argument_type: str=None) -> None:
+                 argument_type: str=None, type: Type=None) -> None:
         """whence: the name of the request variable that should be used
         for this parameter.  Defaults to a request variable of the
         same name as the parameter.
@@ -68,6 +68,10 @@ def __init__(self, whence: str=None, *, converter: Callable[[Any], Any]=None,
 
         argument_type: pass 'body' to extract the parsed JSON
         corresponding to the request body
+
+        type: a hint to typing (using mypy) what the type of this parameter is.
+        Currently only typically necessary if default=None and the type cannot
+        be inferred in another way (eg. via converter).
         """
 
         self.post_var_name = whence

zerver/lib/request.pyi

@@ -6,7 +6,7 @@
 # scan the parameter list for REQ objects and patch the parameters as the true
 # types.
 
-from typing import Any, Callable, Text, TypeVar, Optional, Union
+from typing import Any, Callable, Text, TypeVar, Optional, Union, Type
 from django.http import HttpResponse
 
 from zerver.lib.exceptions import JsonableError as JsonableError
@@ -24,6 +24,7 @@ NotSpecified = _NotSpecified()
 
 def REQ(whence: Optional[str] = None,
         *,
+        type: Type[ResultT] = None,
         converter: Optional[Callable[[str], ResultT]] = None,
         default: Union[_NotSpecified, ResultT] = NotSpecified,
         validator: Optional[Validator] = None,