Initial code for needs_params

src/replit/maqpy/utils.py

@@ -1,6 +1,6 @@
 """Utitilities to make development easier."""
 from functools import wraps
-from typing import Any, Callable
+from typing import Any, Callable, Tuple
 
 import flask
 
@@ -52,3 +52,36 @@ def needs_signin(func: Callable = None, login_html: str = sign_in_snippet) -> Ca
         return decorator(func)
     else:  # called with options, eg @needs_signin(login_html='...')
         return decorator
+
+
+def needs_params(*param_names: str, onerror: Callable[Tuple[str]] = None) -> Callable:
+    """Require paramaters before a handler can be activated.
+
+    Args:
+        param_names (str): The paramaters that must be in the request.
+        onerror (Callable): A function to handle when a paramater is missing. 
+            If no function is specified a handler that returns a descriptive error and
+            400 Bad Request status code will be used.
+
+    Raises:
+        TypeError: No paramaters were provided or an invalid one was provided.
+        NotImplementedError: If the handler is called.
+
+    Returns:
+        Callable: The new handler.
+    """
+    if len(param_names) < 1:
+        raise TypeError("You must specify at least one required paramater name")
+    # If function is used as a decorator with no arguments, the first argument will be
+    # a function, so type check all of the param names to catch mistakes
+    if not all(isinstance(p, str) for p in param_names):
+        raise TypeError("All paramater names should be strings.")
+
+    def decorator(func: Callable) -> Callable:
+        @wraps(func)
+        def handler(*args: Any, **kwargs: Any) -> flask.Response:
+            raise NotImplementedError()
+
+        return handler
+
+    return decorator