Move param_required into the decorators module

endpoints/decorators.py

@@ -1,7 +1,7 @@
 """ Various decorators for endpoint and API handlers. """
 
 from functools import wraps
-from flask import abort
+from flask import abort, request, make_response
 
 import features
 
@@ -35,6 +35,22 @@ def parse_repository_name(include_tag=False,
   return inner
 
 
+def param_required(param_name, allow_body=False):
+  """ Marks a route as requiring a parameter with the given name to exist in the request's arguments
+      or (if allow_body=True) in its body values. If the parameter is not present, the request will
+      fail with a 400.
+  """
+  def wrapper(wrapped):
+    @wraps(wrapped)
+    def decorated(*args, **kwargs):
+      if param_name not in request.args:
+        if not allow_body or param_name not in request.values:
+          abort(make_response('Required param: %s' % param_name, 400))
+      return wrapped(*args, **kwargs)
+    return decorated
+  return wrapper
+
+
 def anon_allowed(func):
   """ Marks a method to allow anonymous access where it would otherwise be disallowed. """
   func.__anon_allowed = True