parameters: add option to specify custom containers (refs #16)

src/graceful/parameters.py

@@ -39,7 +39,7 @@ class BaseParam():
            ``ValueError`` as having required parameters with default
            value has no sense.
 
-        param (str): set to ``True`` if multiple occurences of this parameter
+        many (str): set to ``True`` if multiple occurences of this parameter
            can be included in query string, as a result values for this
            parameter will be always included as a list in params dict. Defaults
            to ``False``.
@@ -70,6 +70,8 @@ def value(self, data):
     spec = None
     type = None
 
+    container = list
+
     def __init__(
             self,
             details,

src/graceful/resources/base.py

@@ -243,11 +243,10 @@ def require_params(self, req):
                 try:
                     if param.many:
                         # params with "many" enabled need special care
-                        params[name] = req.get_param_as_list(
-                            name, param.value,
-                        ) or [
-                            param.default and param.value(param.default)
-                        ]
+                        params[name] = param.container(
+                            req.get_param_as_list(name, param.value) or
+                            [param.default and param.value(param.default)]
+                        )
                     else:
                         # note that if many==False and query parameter
                         # occurs multiple times in qs then it is

tests/test_resources.py

@@ -269,6 +269,40 @@ class SomeResource(Resource):
     assert 'foo' not in params
 
 
+def test_parameter_with_many_and_custom_container_type_object():
+    class StringSetParam(StringParam):
+        # container is simply a type object (it is not a descriptor)
+        # so does not receive self as a parameter
+        container = set
+
+    class SomeResource(Resource):
+        foo = StringSetParam(details="give me foo", many=True)
+
+    env = create_environ(query_string="foo=bar&foo=baz")
+    resource = SomeResource()
+    params = resource.require_params(Request(env))
+
+    assert isinstance(params['foo'], set)
+    assert 'bar' in params['foo'] and 'baz' in params['foo']
+
+
+def test_parameter_with_many_and_custom_container_method():
+    class StringSetParam(StringParam):
+        # container is custom method call ("bound" to param instance)
+        def container(self, values):
+            return set(values)
+
+    class SomeResource(Resource):
+        foo = StringSetParam(details="give me foo", many=True)
+
+    env = create_environ(query_string="foo=bar&foo=baz")
+    resource = SomeResource()
+    params = resource.require_params(Request(env))
+
+    assert isinstance(params['foo'], set)
+    assert 'bar' in params['foo'] and 'baz' in params['foo']
+
+
 def test_parameter_value_errors_translated_to_http_errors(req, resp):
     class InvalidParam(BaseParam):
         def value(self, raw_value):