Implemented nested dict re-cast (aws-cloudformation#174)

Author: JohnPreston

src/cloudformation_cli_python_lib/recast.py

@@ -19,8 +19,7 @@ def recast_object(
         return
     for k, v in json_data.items():
         if isinstance(v, dict):
-            child_cls = _field_to_type(cls.__dataclass_fields__[k].type, k, classes)
-            recast_object(child_cls, v, classes)
+            _recast_nested_dict(cls, json_data, k, v, classes)
         elif isinstance(v, list):
             json_data[k] = _recast_lists(cls, k, v, classes)
         elif isinstance(v, set):
@@ -34,6 +33,37 @@ def recast_object(
             raise InvalidRequest(f"Unsupported type: {type(v)} for {k}")
 
 
+def _recast_nested_dict(
+    cls: Any,
+    json_data: Mapping[str, Any],
+    k: str,
+    v: Dict[str, Any],
+    classes: Dict[str, Any],
+) -> None:
+    """
+    Attempts to recursively cast the dict elements.
+    On KeyError, we know that the "parent" property ,
+    does not have a specific class to be casted to.
+    Therefore we figure out what the "nested object" class might be,
+    recursively cast those,
+    to finally assign to the "parent" dict the right class
+
+    :param Any cls:
+    :param Mapping json_data:
+    :param str k:
+    :param Any v:
+    :param dict classes:
+    """
+    try:
+        child_cls = _field_to_type(cls.__dataclass_fields__[k].type, k, classes)
+        recast_object(child_cls, v, classes)
+    except KeyError:
+        child_cls = _field_to_type(cls.__dataclass_fields__[k].type, k, classes)
+        for _child, _child_definition in v.items():
+            recast_object(child_cls, _child_definition, classes)
+            json_data[k][_child] = _child_definition
+
+
 def _recast_lists(cls: Any, k: str, v: List[Any], classes: Dict[str, Any]) -> List[Any]:
     # Leave as is if type is Any
     if cls is typing.Any:

tests/lib/recast_test.py

@@ -47,6 +47,15 @@ def test_recast_complex_object():
             [{"NestedListInt": "true", "NestedListList": ["1", "2", "3"]}],
             [{"NestedListInt": "false", "NestedListList": ["11", "12", "13"]}],
         ],
+        "NestedObject": {
+            "first_object": {"AttributeA": "AWS_CFN", "AttributeB": "FTW"},
+            "second_object": {"AttributeA": "AllHailPython"},
+            "third_object": {
+                "ListAttribute": ["2.1", "42.0"],
+                "AttributeA": "WeAlsoHaveLists",
+            },
+            "fourth-0bject": {"BoolAttribute": "false", "AttributeB": "ThatIsNotTrue"},
+        },
     }
     expected = {
         "ListSetInt": [{1, 2, 3}],
@@ -79,6 +88,15 @@ def test_recast_complex_object():
             [{"NestedListInt": True, "NestedListList": [1.0, 2.0, 3.0]}],
             [{"NestedListInt": False, "NestedListList": [11.0, 12.0, 13.0]}],
         ],
+        "NestedObject": {
+            "first_object": {"AttributeA": "AWS_CFN", "AttributeB": "FTW"},
+            "second_object": {"AttributeA": "AllHailPython"},
+            "third_object": {
+                "ListAttribute": [2.1, 42.0],
+                "AttributeA": "WeAlsoHaveLists",
+            },
+            "fourth-0bject": {"BoolAttribute": False, "AttributeB": "ThatIsNotTrue"},
+        },
     }
     model = ComplexResourceModel._deserialize(payload)
     assert payload == expected

tests/lib/sample_model.py

@@ -55,6 +55,7 @@ class ResourceModel(BaseModel):
     HttpsUrl: Optional[str]
     Namespace: Optional[str]
     Id: Optional[int]
+    NestedObject: Optional[MutableMapping[str, "_NestedObjectDefinition"]]
 
     @classmethod
     def _deserialize(
@@ -83,6 +84,7 @@ def _deserialize(
             HttpsUrl=json_data.get("HttpsUrl"),
             Namespace=json_data.get("Namespace"),
             Id=json_data.get("Id"),
+            NestedObject=json_data.get("NestedObject"),
         )
 
 
@@ -109,6 +111,32 @@ def _deserialize(
 _NestedList = NestedList
 
 
+@dataclass
+class NestedObjectDefinition(BaseModel):
+    AttributeA: Optional[str]
+    AttributeB: Optional[str]
+    BoolAttribute: Optional[bool]
+    ListAttribute: Optional[Sequence[float]]
+
+    @classmethod
+    def _deserialize(
+        cls: Type["_NestedObjectDefinition"],
+        json_data: Optional[Mapping[str, Any]],
+    ) -> Optional["_NestedObjectDefinition"]:
+        if not json_data:
+            return None
+        return cls(
+            AttributeA=json_data.get("AttributeA"),
+            AttributeB=json_data.get("AttributeB"),
+            BoolAttribute=json_data.get("BoolAttribute"),
+            ListAttribute=json_data.get("ListAttribute"),
+        )
+
+
+# work around possible type aliasing issues when variable has same name as a model
+_NestedObjectDefinition = NestedObjectDefinition
+
+
 @dataclass
 class AList(BaseModel):
     DeeperBool: Optional[bool]