feat(Request): Add optional min, max arguments to req.get_param_as_int

This patch makes it easy to validate integer parameters.

Closes #103

falcon/request.py

@@ -355,7 +355,7 @@ class Request(object):
         description = 'The "' + name + '" query parameter is required.'
         raise HTTPBadRequest('Missing query parameter', description)
 
-    def get_param_as_int(self, name, required=False):
+    def get_param_as_int(self, name, required=False, min=None, max=None):
         """Return the value of a query string parameter as an int
 
         Args:
@@ -363,6 +363,11 @@ class Request(object):
             required: Set to True to raise HTTPBadRequest instead of returning
                 gracefully when the parameter is not found or is not an
                 integer (default False)
+            min: Set to the minimum value allowed for this param. If the param
+                is found and it is less than min, an HTTPError is raised.
+            max: Set to the maximum value allowed for this param. If the param
+                is found and its value is greater than max, an HTTPError is
+                raised.
 
         Returns:
             The value of the param if it is found and can be converted to an
@@ -371,7 +376,9 @@ class Request(object):
 
         Raises
             HTTPBadRequest: The param was not found in the request, even though
-                it was required to be there.
+                it was required to be there. Also raised if the param's value
+                falls outside the given interval, i.e., the value must be in
+                the interval: min <= value <= max to avoid triggering an error.
 
         """
 
@@ -380,12 +387,24 @@ class Request(object):
         if name in self._params:
             val = self._params[name]
             try:
-                return int(val)
+                val = int(val)
             except ValueError:
                 description = ('The value of the "' + name + '" query '
                                'parameter must be an integer.')
                 raise InvalidParamValueError(description)
 
+            if min is not None and val < min:
+                description = ('The value of the "' + name + '" query '
+                               'parameter must be at least %d') % min
+                raise InvalidHeaderValueError(description)
+
+            if max is not None and max < val:
+                description = ('The value of the "' + name + '" query '
+                               'parameter may not exceed %d') % max
+                raise InvalidHeaderValueError(description)
+
+            return val
+
         if not required:
             return None
 

tests/test_query_params.py

@@ -71,6 +71,75 @@ class TestQueryParams(testing.TestBase):
                           'marker')
         self.assertEquals(req.get_param_as_int('limit'), 25)
 
+        self.assertEquals(
+            req.get_param_as_int('limit', min=1, max=50), 25)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'limit', min=0, max=10)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'limit', min=0, max=24)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'limit', min=30, max=24)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'limit', min=30, max=50)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', min=1), 25)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', max=50), 25)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', max=25), 25)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', max=26), 25)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', min=25), 25)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', min=24), 25)
+
+        self.assertEquals(
+            req.get_param_as_int('limit', min=-24), 25)
+
+    def test_int_neg(self):
+        query_string = 'marker=deadbeef&pos=-7'
+        self.simulate_request('/', query_string=query_string)
+
+        req = self.resource.req
+        self.assertEquals(req.get_param_as_int('pos'), -7)
+
+        self.assertEquals(
+            req.get_param_as_int('pos', min=-10, max=10), -7)
+
+        self.assertEquals(
+            req.get_param_as_int('pos', max=10), -7)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'pos', min=-6, max=0)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'pos', min=-6)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'pos', min=0, max=10)
+
+        self.assertRaises(
+            falcon.HTTPBadRequest,
+            req.get_param_as_int, 'pos', min=0, max=10)
+
     def test_boolean(self):
         query_string = 'echo=true&doit=false&bogus=0&bogus2=1'
         self.simulate_request('/', query_string=query_string)