Fix serialization of repeated fields with empty messages (#180)

Extend test config and utils to support exclusion of certain json samples from
testing for symetry.

src/betterproto/__init__.py

@@ -739,9 +739,18 @@ class Message(ABC):
                     output += _serialize_single(meta.number, TYPE_BYTES, buf)
                 else:
                     for item in value:
-                        output += _serialize_single(
+                        output += (
-                            meta.number, meta.proto_type, item, wraps=meta.wraps or ""
+                            _serialize_single(
+                                meta.number,
+                                meta.proto_type,
+                                item,
+                                wraps=meta.wraps or "",
                             )
+                            # if it's an empty message it still needs to be represented
+                            # as an item in the repeated list
+                            or b"\n\x00"
+                        )
+
             elif isinstance(value, dict):
                 for k, v in value.items():
                     assert meta.map_types

tests/inputs/config.py

@@ -19,3 +19,10 @@ services = {
     "example_service",
     "empty_service",
 }
+
+
+# Indicate json sample messages to skip when testing that json (de)serialization
+# is symmetrical becuase some cases legitimately are not symmetrical.
+# Each key references the name of the test scenario and the values in the tuple
+# Are the names of the json files.
+non_symmetrical_json = {"empty_repeated": ("empty_repeated",)}

tests/inputs/empty_repeated/empty_repeated.json

@@ -0,0 +1,3 @@
+{
+  "msg": [{"values":[]}]
+}

tests/inputs/empty_repeated/empty_repeated.proto

@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+message MessageA {
+  repeated float values = 1;
+}
+
+message Test {
+  repeated MessageA msg = 1;
+}

tests/inputs/oneof/test_oneof.py

@@ -5,11 +5,11 @@ from tests.util import get_test_case_json_data
 
 def test_which_count():
     message = Test()
-    message.from_json(get_test_case_json_data("oneof")[0])
+    message.from_json(get_test_case_json_data("oneof")[0].json)
     assert betterproto.which_one_of(message, "foo") == ("pitied", 100)
 
 
 def test_which_name():
     message = Test()
-    message.from_json(get_test_case_json_data("oneof", "oneof_name.json")[0])
+    message.from_json(get_test_case_json_data("oneof", "oneof_name.json")[0].json)
     assert betterproto.which_one_of(message, "foo") == ("pitier", "Mr. T")

tests/inputs/oneof_enum/test_oneof_enum.py

@@ -15,7 +15,7 @@ def test_which_one_of_returns_enum_with_default_value():
     """
     message = Test()
     message.from_json(
-        get_test_case_json_data("oneof_enum", "oneof_enum-enum-0.json")[0]
+        get_test_case_json_data("oneof_enum", "oneof_enum-enum-0.json")[0].json
     )
 
     assert message.move == Move(
@@ -31,7 +31,7 @@ def test_which_one_of_returns_enum_with_non_default_value():
     """
     message = Test()
     message.from_json(
-        get_test_case_json_data("oneof_enum", "oneof_enum-enum-1.json")[0]
+        get_test_case_json_data("oneof_enum", "oneof_enum-enum-1.json")[0].json
     )
     assert message.move == Move(
         x=0, y=0
@@ -42,7 +42,7 @@ def test_which_one_of_returns_enum_with_non_default_value():
 
 def test_which_one_of_returns_second_field_when_set():
     message = Test()
-    message.from_json(get_test_case_json_data("oneof_enum")[0])
+    message.from_json(get_test_case_json_data("oneof_enum")[0].json)
     assert message.move == Move(x=2, y=3)
     assert message.signal == Signal.PASS
     assert betterproto.which_one_of(message, "action") == ("move", Move(x=2, y=3))

tests/test_inputs.py

@@ -5,7 +5,7 @@ import os
 import sys
 from collections import namedtuple
 from types import ModuleType
-from typing import Any, Dict, List, Set
+from typing import Any, Dict, List, Set, Tuple
 
 import pytest
 
@@ -29,7 +29,12 @@ from google.protobuf.json_format import Parse
 
 
 class TestCases:
-    def __init__(self, path, services: Set[str], xfail: Set[str]):
+    def __init__(
+        self,
+        path,
+        services: Set[str],
+        xfail: Set[str],
+    ):
         _all = set(get_directories(path)) - {"__pycache__"}
         _services = services
         _messages = (_all - services) - {"__pycache__"}
@@ -175,14 +180,17 @@ def test_message_json(repeat, test_data: TestData) -> None:
     plugin_module, _, json_data = test_data
 
     for _ in range(repeat):
-        for json_sample in json_data:
+        for sample in json_data:
+            if sample.belongs_to(test_input_config.non_symmetrical_json):
+                continue
+
             message: betterproto.Message = plugin_module.Test()
 
-            message.from_json(json_sample)
+            message.from_json(sample.json)
             message_json = message.to_json(0)
 
             assert dict_replace_nans(json.loads(message_json)) == dict_replace_nans(
-            json.loads(json_sample)
+                json.loads(sample.json)
             )
 
 
@@ -195,13 +203,13 @@ def test_service_can_be_instantiated(test_data: TestData) -> None:
 def test_binary_compatibility(repeat, test_data: TestData) -> None:
     plugin_module, reference_module, json_data = test_data
 
-    for json_sample in json_data:
+    for sample in json_data:
-        reference_instance = Parse(json_sample, reference_module().Test())
+        reference_instance = Parse(sample.json, reference_module().Test())
         reference_binary_output = reference_instance.SerializeToString()
 
         for _ in range(repeat):
             plugin_instance_from_json: betterproto.Message = (
-                plugin_module.Test().from_json(json_sample)
+                plugin_module.Test().from_json(sample.json)
             )
             plugin_instance_from_binary = plugin_module.Test.FromString(
                 reference_binary_output

tests/util.py

@@ -1,11 +1,11 @@
 import asyncio
+from dataclasses import dataclass
 import importlib
 import os
-import pathlib
-import sys
 from pathlib import Path
+import sys
 from types import ModuleType
-from typing import Callable, Generator, List, Optional, Union
+from typing import Callable, Dict, Generator, List, Optional, Tuple, Union
 
 os.environ["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = "python"
 
@@ -47,11 +47,24 @@ async def protoc(
     return stdout, stderr, proc.returncode
 
 
-def get_test_case_json_data(test_case_name: str, *json_file_names: str) -> List[str]:
+@dataclass
+class TestCaseJsonFile:
+    json: str
+    test_name: str
+    file_name: str
+
+    def belongs_to(self, non_symmetrical_json: Dict[str, Tuple[str, ...]]):
+        return self.file_name in non_symmetrical_json.get(self.test_name, tuple())
+
+
+def get_test_case_json_data(
+    test_case_name: str, *json_file_names: str
+) -> List[TestCaseJsonFile]:
     """
     :return:
-        A list of all files found in "inputs_path/test_case_name" with names matching
+        A list of all files found in "{inputs_path}/test_case_name" with names matching
-        f"{test_case_name}.json" or f"{test_case_name}_*.json", OR given by json_file_names
+        f"{test_case_name}.json" or f"{test_case_name}_*.json", OR given by
+        json_file_names
     """
     test_case_dir = inputs_path.joinpath(test_case_name)
     possible_file_paths = [
@@ -65,7 +78,11 @@ def get_test_case_json_data(test_case_name: str, *json_file_names: str) -> List[
         if not test_data_file_path.exists():
             continue
         with test_data_file_path.open("r") as fh:
-            result.append(fh.read())
+            result.append(
+                TestCaseJsonFile(
+                    fh.read(), test_case_name, test_data_file_path.name.split(".")[0]
+                )
+            )
 
     return result
 
@@ -86,7 +103,7 @@ def find_module(
     if predicate(module):
         return module
 
-    module_path = pathlib.Path(*module.__path__)
+    module_path = Path(*module.__path__)
 
     for sub in [sub.parent for sub in module_path.glob("**/__init__.py")]:
         if sub == module_path: