Provide better type checking for values in from_dict

tests/test_dict.py

@@ -5,8 +5,8 @@
 
 
 class TestDict(unittest.TestCase):
-    def test_exclusive(self):
-        d = {
+    def setUp(self):
+        self.d = {
             "Cpu": 1,
             "Environment": [
                 {
@@ -34,8 +34,9 @@ def test_exclusive(self):
             ]
         }
 
+    def test_valid_data(self):
         t = Template()
-        cd = ecs.ContainerDefinition.from_dict("mycontainer", d)
+        cd = ecs.ContainerDefinition.from_dict("mycontainer", self.d)
         td = ecs.TaskDefinition(
                 "taskdef",
                 ContainerDefinitions=[cd],
@@ -45,5 +46,32 @@ def test_exclusive(self):
         t.add_resource(td)
         t.to_json()
 
+    def test_invalid_toplevel_property(self):
+        self.d["BlahInvalid"] = "Invalid"
+        with self.assertRaises(AttributeError):
+            ecs.ContainerDefinition.from_dict("mycontainer", self.d)
+
+    def test_invalid_sub_property(self):
+        self.d["Environment"][0]["BlahInvalid"] = "Invalid"
+        with self.assertRaises(AttributeError):
+            ecs.ContainerDefinition.from_dict("mycontainer", self.d)
+
+    def test_toplevel_helper_fn(self):
+        self.d["Cpu"] = Ref("MyCPU")
+        cd = ecs.ContainerDefinition.from_dict("mycontainer", self.d)
+        self.assertEquals(cd.Cpu.data, {"Ref": "MyCPU"})
+
+    def test_sub_property_helper_fn(self):
+        self.d["Environment"][0]["Value"] = Ref("RegistryStorage")
+        cd = ecs.ContainerDefinition.from_dict("mycontainer", self.d)
+        self.assertEquals(cd.Environment[0].Value.data,
+                          {"Ref": "RegistryStorage"})
+
+    def test_invalid_subproperty_definition(self):
+        self.d["Environment"][0] = "BadValue"
+        with self.assertRaises(ValueError):
+            ecs.ContainerDefinition.from_dict("mycontainer", self.d)
+
+
 if __name__ == '__main__':
     unittest.main()

troposphere/__init__.py

@@ -4,6 +4,7 @@
 # See LICENSE file for full license.
 
 
+import collections
 import json
 import re
 import sys
@@ -162,10 +163,50 @@ def validate(self):
         pass
 
     @classmethod
-    def from_dict(cls, title, dict):
-        obj = cls(title)
-        obj.properties.update(dict)
-        return obj
+    def _from_dict(cls, title=None, **kwargs):
+        props = {}
+        for prop_name, value in kwargs.items():
+            try:
+                prop_attrs = cls.props[prop_name]
+            except KeyError:
+                raise AttributeError("Object type %s does not have a "
+                                     "%s property." % (cls.__name__,
+                                                       prop_name))
+            prop_type = prop_attrs[0]
+            if prop_name in kwargs:
+                value = kwargs[prop_name]
+                is_aws_object = False
+                try:
+                    is_aws_object = issubclass(prop_type, BaseAWSObject)
+                # prop_type isn't a class
+                except TypeError:
+                    pass
+                if is_aws_object:
+                    if not isinstance(value, collections.Mapping):
+                        raise ValueError("Property definition for %s must be "
+                                         "a Mapping type" % prop_name)
+                    value = prop_type._from_dict(**value)
+
+                if isinstance(prop_type, list):
+                    if not isinstance(value, list):
+                        raise TypeError("Attribute %s must be a "
+                                        "list." % prop_name)
+                    new_value = []
+                    for v in value:
+                        if not isinstance(v, collections.Mapping):
+                            raise ValueError(
+                                "Property definition for %s must be "
+                                "a list of Mapping types" % prop_name)
+                        new_value.append(prop_type[0]._from_dict(**v))
+                    value = new_value
+                props[prop_name] = value
+        if title:
+            return cls(title, **props)
+        return cls(**props)
+
+    @classmethod
+    def from_dict(cls, title, d):
+        return cls._from_dict(title, **d)
 
     def JSONrepr(self):
         for k, (_, required) in self.props.items():