betterproto: support Struct and Value

src/betterproto/__init__.py

@@ -55,7 +55,6 @@
     hybridmethod,
 )
 
-
 if TYPE_CHECKING:
     from _typeshed import (
         SupportsRead,
@@ -1404,6 +1403,15 @@ def to_dict(
         Dict[:class:`str`, Any]
             The JSON serializable dict representation of this object.
         """
+        # Mirror of from_dict: Struct's `fields` member is transparently
+        # dispatched through instead.
+        if isinstance(self, Struct):
+            output = {**self.fields}
+            for k in self.fields:
+                if hasattr(self.fields[k], "to_dict"):
+                    output[k] = self.fields[k].to_dict(casing, include_default_values)
+            return output
+
         output: Dict[str, Any] = {}
         field_types = self._type_hints()
         defaults = self._betterproto.default_gen
@@ -1522,6 +1530,12 @@ def to_dict(
 
     @classmethod
     def _from_dict_init(cls, mapping: Mapping[str, Any]) -> Mapping[str, Any]:
+        # Special case: google.protobuf.Struct has a single fields member but
+        # behaves like a transparent JSON object, so it needs to first be munged
+        # into `{fields: mapping}`.
+        if cls == Struct:
+            mapping = {"fields": mapping}
+
         init_kwargs: Dict[str, Any] = {}
         for key, value in mapping.items():
             field_name = safe_snake_case(key)
@@ -1552,7 +1566,7 @@ def _from_dict_init(cls, mapping: Mapping[str, Any]) -> Mapping[str, Any]:
                         if isinstance(value, list)
                         else sub_cls.from_dict(value)
                     )
-            elif meta.map_types and meta.map_types[1] == TYPE_MESSAGE:
+            elif meta.map_types and meta.map_types[1] == TYPE_MESSAGE and cls != Struct:
                 sub_cls = cls._betterproto.cls_by_field[f"{field_name}.value"]
                 value = {k: sub_cls.from_dict(v) for k, v in value.items()}
             else:
@@ -1582,6 +1596,7 @@ def _from_dict_init(cls, mapping: Mapping[str, Any]) -> Mapping[str, Any]:
                     )
 
             init_kwargs[field_name] = value
+
         return init_kwargs
 
     @hybridmethod
@@ -1926,6 +1941,7 @@ def which_one_of(message: Message, group_name: str) -> Tuple[str, Optional[Any]]
     Int32Value,
     Int64Value,
     StringValue,
+    Struct,
     Timestamp,
     UInt32Value,
     UInt64Value,

tests/test_struct.py

@@ -0,0 +1,22 @@
+import json
+
+from betterproto.lib.google.protobuf import Struct
+
+
+def test_struct_roundtrip():
+    data = {
+        "foo": "bar",
+        "baz": None,
+        "quux": 123,
+        "zap": [1, {"two": 3}, "four"],
+    }
+    data_json = json.dumps(data)
+
+    struct_from_dict = Struct().from_dict(data)
+    assert struct_from_dict.fields == data
+    assert struct_from_dict.to_json() == data_json
+
+    struct_from_json = Struct().from_json(data_json)
+    assert struct_from_json.fields == data
+    assert struct_from_json == struct_from_dict
+    assert struct_from_json.to_json() == data_json