Support for repeated message fields

README.md

@@ -5,7 +5,7 @@
 - [x] Zig-zag signed fields (sint32, sint64)
 - [x] Don't encode zero values for nested types
 - [x] Enums
-- [ ] Repeated message fields
+- [x] Repeated message fields
 - [ ] Maps
 - [ ] Support passthrough of unknown fields
 - [ ] Refs to nested types

betterproto/__init__.py

@@ -2,6 +2,7 @@ from abc import ABC
 import json
 import struct
 from typing import (
+    get_type_hints,
     Union,
     Generator,
     Any,
@@ -15,6 +16,8 @@ from typing import (
 )
 import dataclasses
 
+import inspect
+
 # Proto 3 data types
 TYPE_ENUM = "enum"
 TYPE_BOOL = "bool"
@@ -283,35 +286,6 @@ def decode_varint(buffer: bytes, pos: int, signed: bool = False) -> Tuple[int, i
             raise ValueError("Too many bytes when decoding varint.")
 
 
-def _postprocess_single(
-    wire_type: int, meta: FieldMetadata, field: Any, value: Any
-) -> Any:
-    """Adjusts values after parsing."""
-    if wire_type == WIRE_VARINT:
-        if meta.proto_type in ["int32", "int64"]:
-            bits = int(meta.proto_type[3:])
-            value = value & ((1 << bits) - 1)
-            signbit = 1 << (bits - 1)
-            value = int((value ^ signbit) - signbit)
-        elif meta.proto_type in ["sint32", "sint64"]:
-            # Undo zig-zag encoding
-            value = (value >> 1) ^ (-(value & 1))
-    elif wire_type in [WIRE_FIXED_32, WIRE_FIXED_64]:
-        fmt = _pack_fmt(meta.proto_type)
-        value = struct.unpack(fmt, value)[0]
-    elif wire_type == WIRE_LEN_DELIM:
-        if meta.proto_type in ["string"]:
-            value = value.decode("utf-8")
-        elif meta.proto_type in ["message"]:
-            orig = value
-            value = field.default_factory()
-            if isinstance(value, Message):
-                # If it's a message (instead of e.g. list) then keep going!
-                value.parse(orig)
-
-    return value
-
-
 @dataclasses.dataclass(frozen=True)
 class ParsedField:
     number: int
@@ -388,6 +362,41 @@ class Message(ABC):
 
         return output
 
+    def _cls_for(self, field: dataclasses.Field) -> Type:
+        """Get the message class for a field from the type hints."""
+        module = inspect.getmodule(self)
+        type_hints = get_type_hints(self, vars(module))
+        cls = type_hints[field.name]
+        if hasattr(cls, "__args__"):
+            print(type_hints[field.name].__args__[0])
+            cls = type_hints[field.name].__args__[0]
+        return cls
+
+    def _postprocess_single(
+        self, wire_type: int, meta: FieldMetadata, field: dataclasses.Field, value: Any
+    ) -> Any:
+        """Adjusts values after parsing."""
+        if wire_type == WIRE_VARINT:
+            if meta.proto_type in ["int32", "int64"]:
+                bits = int(meta.proto_type[3:])
+                value = value & ((1 << bits) - 1)
+                signbit = 1 << (bits - 1)
+                value = int((value ^ signbit) - signbit)
+            elif meta.proto_type in ["sint32", "sint64"]:
+                # Undo zig-zag encoding
+                value = (value >> 1) ^ (-(value & 1))
+        elif wire_type in [WIRE_FIXED_32, WIRE_FIXED_64]:
+            fmt = _pack_fmt(meta.proto_type)
+            value = struct.unpack(fmt, value)[0]
+        elif wire_type == WIRE_LEN_DELIM:
+            if meta.proto_type in ["string"]:
+                value = value.decode("utf-8")
+            elif meta.proto_type in ["message"]:
+                cls = self._cls_for(field)
+                value = cls().parse(value)
+
+        return value
+
     def parse(self, data: bytes) -> T:
         """
         Parse the binary encoded Protobuf into this message instance. This
@@ -416,10 +425,12 @@ class Message(ABC):
                         else:
                             decoded, pos = decode_varint(parsed.value, pos)
                             wire_type = WIRE_VARINT
-                        decoded = _postprocess_single(wire_type, meta, field, decoded)
+                        decoded = self._postprocess_single(
+                            wire_type, meta, field, decoded
+                        )
                         value.append(decoded)
                 else:
-                    value = _postprocess_single(
+                    value = self._postprocess_single(
                         parsed.wire_type, meta, field, parsed.value
                     )
 
@@ -445,7 +456,13 @@ class Message(ABC):
             meta = FieldMetadata.get(field)
             v = getattr(self, field.name)
             if meta.proto_type == "message":
-                v = v.to_dict()
+                if isinstance(v, list):
+                    # Convert each item.
+                    v = [i.to_dict() for i in v]
+                    # Filter out empty items which we won't serialize.
+                    v = [i for i in v if i]
+                else:
+                    v = v.to_dict()
                 if v:
                     output[field.name] = v
             elif v != field.default:
@@ -461,7 +478,14 @@ class Message(ABC):
             meta = FieldMetadata.get(field)
             if field.name in value:
                 if meta.proto_type == "message":
-                    getattr(self, field.name).from_dict(value[field.name])
+                    v = getattr(self, field.name)
+                    print(v, value[field.name])
+                    if isinstance(v, list):
+                        cls = self._cls_for(field)
+                        for i in range(len(value[field.name])):
+                            v.append(cls().from_dict(value[field.name][i]))
+                    else:
+                        v.from_dict(value[field.name])
                 else:
                     setattr(self, field.name, value[field.name])
         return self

betterproto/tests/repeatedmessage.json

@@ -0,0 +1,10 @@
+{
+  "greetings": [
+    {
+      "greeting": "hello"
+    },
+    {
+      "greeting": "hi"
+    }
+  ]
+}

betterproto/tests/repeatedmessage.proto

@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+message Test {
+  repeated Sub greetings = 1;
+}
+
+message Sub {
+  string greeting = 1;
+}