Support pass-through of unknown fields

betterproto/__init__.py

@@ -341,17 +341,19 @@ class ParsedField:
     number: int
     wire_type: int
     value: Any
+    raw: bytes
 
 
 def parse_fields(value: bytes) -> Generator[ParsedField, None, None]:
     i = 0
     while i < len(value):
+        start = i
         num_wire, i = decode_varint(value, i)
         # print(num_wire, i)
         number = num_wire >> 3
         wire_type = num_wire & 0x7
 
-        decoded: Any
+        decoded: Any = None
         if wire_type == 0:
             decoded, i = decode_varint(value, i)
         elif wire_type == 1:
@@ -362,12 +364,12 @@ def parse_fields(value: bytes) -> Generator[ParsedField, None, None]:
             i += length
         elif wire_type == 5:
             decoded, i = value[i : i + 4], i + 4
-        else:
-            raise NotImplementedError(f"Wire type {wire_type}")
 
         # print(ParsedField(number=number, wire_type=wire_type, value=decoded))
 
-        yield ParsedField(number=number, wire_type=wire_type, value=decoded)
+        yield ParsedField(
+            number=number, wire_type=wire_type, value=decoded, raw=value[start:i]
+        )
 
 
 # Bound type variable to allow methods to return `self` of subclasses
@@ -415,6 +417,7 @@ class Message(ABC):
 
         # Now that all the defaults are set, reset it!
         self.__dict__["serialized_on_wire"] = False
+        self.__dict__["_unknown_fields"] = b""
 
     def __setattr__(self, attr: str, value: Any) -> None:
         if attr != "serialized_on_wire":
@@ -469,7 +472,7 @@ class Message(ABC):
                     meta.number, meta.proto_type, value, serialize_empty=serialize_empty
                 )
 
-        return output
+        return output + self._unknown_fields
 
     # For compatibility with other libraries
     SerializeToString = __bytes__
@@ -571,8 +574,7 @@ class Message(ABC):
                 else:
                     setattr(self, field.name, value)
             else:
-                # TODO: handle unknown fields
-                pass
+                self._unknown_fields += parsed.raw
 
         return self