Two bug fixes in map field binary parsing

protobuf/CHANGELOG.md

@@ -16,6 +16,8 @@
 * Avoid copying when reading map fields of read-only messages. ([#741])
 * Fix `PbMap._isReadonly` field initialization in `PbMap.unmodifiable`.
   ([#741])
+* Fix decoding map fields when key or value (or both) fields of a map entry is
+  missing. ([#719], [#745])
 
 [#183]: https://github.com/google/protobuf.dart/issues/183
 [#644]: https://github.com/google/protobuf.dart/pull/644
@@ -29,6 +31,8 @@
 [#721]: https://github.com/google/protobuf.dart/pull/721
 [#681]: https://github.com/google/protobuf.dart/pull/681
 [#741]: https://github.com/google/protobuf.dart/pull/741
+[#719]: https://github.com/google/protobuf.dart/issues/719
+[#745]: https://github.com/google/protobuf.dart/pull/745
 
 ## 2.1.0
 

protobuf/lib/src/protobuf/builder_info.dart

@@ -241,11 +241,12 @@ class BuilderInfo {
       List<ProtobufEnum>? enumValues,
       ProtobufEnum? defaultEnumValue,
       PackageName packageName = const PackageName(''),
-      String? protoName}) {
+      String? protoName,
+      dynamic valueDefaultOrMaker}) {
     var mapEntryBuilderInfo = BuilderInfo(entryClassName, package: packageName)
       ..add(PbMap._keyFieldNumber, 'key', keyFieldType, null, null, null, null)
-      ..add(PbMap._valueFieldNumber, 'value', valueFieldType, null,
-          valueCreator, valueOf, enumValues);
+      ..add(PbMap._valueFieldNumber, 'value', valueFieldType,
+          valueDefaultOrMaker, valueCreator, valueOf, enumValues);
 
     addMapField<K, V>(tagNumber, name, keyFieldType, valueFieldType,
         mapEntryBuilderInfo, valueCreator,

protoc_plugin/CHANGELOG.md

@@ -22,10 +22,14 @@
   ```
 * Export public dependencies (`import public`s in proto files) in
   `.pbenum.dart` files, same as `.pb.dart` files. ([9aad6aa])
+* Fix decoding map fields when key or value (or both) fields of a map entry is
+  missing. ([#719], [#745])
 
 [#679]: https://github.com/google/protobuf.dart/pull/679
 [#703]: https://github.com/google/protobuf.dart/pull/703
 [9aad6aa]: https://github.com/google/protobuf.dart/commits/9aad6aa
+[#719]: https://github.com/google/protobuf.dart/issues/719
+[#745]: https://github.com/google/protobuf.dart/pull/745
 
 ## 20.0.1
 

protoc_plugin/lib/src/protobuf_field.dart

@@ -204,8 +204,13 @@ class ProtobufField {
       final generator = baseType.generator as MessageGenerator;
       var key = generator._fieldList[0];
       var value = generator._fieldList[1];
-      var keyType = key.baseType.getDartType(parent.fileGen!);
-      var valueType = value.baseType.getDartType(parent.fileGen!);
+
+      // Key type is an integer type or string. No need to specify the default
+      // value as the library knows the defaults for integer and string fields.
+      final keyType = key.baseType.getDartType(parent.fileGen!);
+
+      // Value type can be anything other than another map.
+      final valueType = value.baseType.getDartType(parent.fileGen!);
 
       invocation = 'm<$keyType, $valueType>';
 
@@ -214,10 +219,12 @@ class ProtobufField {
       named['valueFieldType'] = value.typeConstant;
       if (value.baseType.isMessage || value.baseType.isGroup) {
         named['valueCreator'] = '$valueType.create';
+        named['valueDefaultOrMaker'] = value.generateDefaultFunction();
       }
       if (value.baseType.isEnum) {
         named['valueOf'] = '$valueType.valueOf';
         named['enumValues'] = '$valueType.values';
+        named['valueDefaultOrMaker'] = value.generateDefaultFunction();
         named['defaultEnumValue'] = value.generateDefaultFunction();
       }
       if (package != '') {

protoc_plugin/test/map_field_test.dart

@@ -370,4 +370,81 @@ void main() {
     map2[1] = 2;
     expect(msg2.int32ToInt32Field[1], 2);
   });
+
+  test('Parses empty map fields', () {
+    // Map fields are encoded as messages (as length-delimited fields). Check
+    // that we handle 0 length fields. (#719)
+    {
+      final messageBytes = <int>[
+        (5 << 3) | 2, // tag = 5, wire type = 2 (length delimited)
+        0, // length = 0
+      ];
+      final message = TestMap.fromBuffer(messageBytes);
+      expect(
+          message, TestMap()..int32ToMessageField[0] = TestMap_MessageValue());
+    }
+
+    {
+      final messageBytes = <int>[
+        (4 << 3) | 2, // tag = 4, wire type = 2 (length delimited)
+        0, // length = 0
+      ];
+      final message = TestMap.fromBuffer(messageBytes);
+      expect(
+          message, TestMap()..int32ToEnumField[0] = TestMap_EnumValue.DEFAULT);
+    }
+  });
+
+  test('Parses map field with just key', () {
+    // Similar to the case above, but the field just has key (no value)
+    {
+      final messageBytes = <int>[
+        (5 << 3) | 2, // tag = 5, wire type = 2 (length delimited)
+        2, // length = 2
+        (1 << 3) | 0, // tag = 1 (map key), wire type = 0 (varint)
+        1, // key = 1
+      ];
+      final message = TestMap.fromBuffer(messageBytes);
+      expect(
+          message, TestMap()..int32ToMessageField[1] = TestMap_MessageValue());
+    }
+
+    {
+      final messageBytes = <int>[
+        (4 << 3) | 2, // tag = 4, wire type = 2 (length delimited)
+        2, // length = 2
+        (1 << 3) | 0, // tag = 1 (map key), wire type = 0 (varint)
+        1, // key = 1
+      ];
+      final message = TestMap.fromBuffer(messageBytes);
+      expect(
+          message, TestMap()..int32ToEnumField[1] = TestMap_EnumValue.DEFAULT);
+    }
+  });
+
+  test('Parses map field with just key', () {
+    // Similar to the case above, but the field just has value (no key)
+    {
+      final messageBytes = <int>[
+        (5 << 3) | 2, // tag = 5, wire type = 2 (length delimited)
+        2, // length = 2
+        (2 << 3) | 2, // tag = 2 (map value), wire type = 2 (length delimited)
+        0, // length = 0 (empty message)
+      ];
+      final message = TestMap.fromBuffer(messageBytes);
+      expect(
+          message, TestMap()..int32ToMessageField[0] = TestMap_MessageValue());
+    }
+
+    {
+      final messageBytes = <int>[
+        (4 << 3) | 2, // tag = 4, wire type = 2 (length delimited)
+        2, // length = 2
+        (2 << 3) | 2, // tag = 2 (map value), wire type = 2 (length delimited)
+        1, // enum value = 1
+      ];
+      final message = TestMap.fromBuffer(messageBytes);
+      expect(message, TestMap()..int32ToEnumField[0] = TestMap_EnumValue.BAR);
+    }
+  });
 }