Enforce serialize_empty for repeated fields (#417)

src/betterproto/__init__.py

@@ -806,6 +806,7 @@ class Message(ABC):
                                 meta.proto_type,
                                 item,
                                 wraps=meta.wraps or "",
+                                serialize_empty=True,
                             )
                             # if it's an empty message it still needs to be represented
                             # as an item in the repeated list

tests/inputs/regression_387/regression_387.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+package regression_387;
+
+message Test {
+  uint64 id = 1;
+}
+
+message ParentElement {
+  string name = 1;
+  repeated Test elems = 2;
+}

tests/inputs/regression_387/test_regression_387.py

@@ -0,0 +1,12 @@
+from tests.output_betterproto.regression_387 import (
+    ParentElement,
+    Test,
+)
+
+
+def test_regression_387():
+    el = ParentElement(name="test", elems=[Test(id=0), Test(id=42)])
+    binary = bytes(el)
+    decoded = ParentElement().parse(binary)
+    assert decoded == el
+    assert decoded.elems == [Test(id=0), Test(id=42)]

tests/inputs/regression_414/regression_414.proto

@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package regression_414;
+
+message Test {
+  bytes body = 1;
+  bytes auth = 2;
+  repeated bytes signatures = 3;
+}

tests/inputs/regression_414/test_regression_414.py

@@ -0,0 +1,15 @@
+from tests.output_betterproto.regression_414 import Test
+
+
+def test_full_cycle():
+    body = bytes([0, 1])
+    auth = bytes([2, 3])
+    sig = [b""]
+
+    obj = Test(body=body, auth=auth, signatures=sig)
+
+    decoded = Test().parse(bytes(obj))
+    assert decoded == obj
+    assert decoded.body == body
+    assert decoded.auth == auth
+    assert decoded.signatures == sig