Implement deepCopy as copying, instead of merge

protobuf/lib/src/protobuf/extension_field_set.dart

@@ -6,11 +6,20 @@ part of protobuf;
 
 class _ExtensionFieldSet {
   final _FieldSet _parent;
-  final Map<int, Extension> _info = <int, Extension>{};
-  final Map<int, dynamic> _values = <int, dynamic>{};
-  bool _isReadOnly = false;
 
-  _ExtensionFieldSet(this._parent);
+  final Map<int, Extension> _info;
+
+  final Map<int, dynamic> _values;
+
+  bool _isReadOnly;
+
+  _ExtensionFieldSet(this._parent)
+      : _info = <int, Extension>{},
+        _values = <int, dynamic>{},
+        _isReadOnly = false;
+
+  _ExtensionFieldSet._(
+      this._parent, this._info, this._values, this._isReadOnly);
 
   Extension? _getInfoOrNull(int? tagNumber) => _info[tagNumber];
 
@@ -203,4 +212,30 @@ class _ExtensionFieldSet {
           'use `ExtensionRegistry.reparseMessage`.');
     }
   }
+
+  _ExtensionFieldSet deepCopy(_FieldSet parent, {bool freeze = false}) {
+    final values = <int, dynamic>{};
+
+    for (final entry in _values.entries) {
+      final key = entry.key;
+      final value = entry.value;
+
+      if (value is PbMap) {
+        values[key] = value.deepCopy(freeze: freeze) as dynamic;
+      } else if (value is PbList) {
+        values[key] = value.deepCopy(freeze: freeze) as dynamic;
+      } else if (value is GeneratedMessage) {
+        values[key] = value.deepCopy(freeze: freeze) as dynamic;
+      } else {
+        values[key] = value;
+      }
+    }
+
+    return _ExtensionFieldSet._(
+      parent,
+      _info,
+      values,
+      freeze,
+    );
+  }
 }

protobuf/lib/src/protobuf/field_set.dart

@@ -78,6 +78,9 @@ class _FieldSet {
       : _values = _makeValueList(meta.byIndex.length),
         _oneofCases = meta.oneofs.isEmpty ? null : <int, int>{};
 
+  _FieldSet._(this._message, this._eventPlugin, this._values, this._extensions,
+      this._unknownFields, this._frozenState, this._oneofCases);
+
   static List _makeValueList(int length) {
     if (length == 0) return _zeroList;
     return List.filled(length, null, growable: false);
@@ -897,4 +900,35 @@ class _FieldSet {
 
     _oneofCases?.addAll(original._oneofCases!);
   }
+
+  _FieldSet deepCopy(GeneratedMessage message, {bool freeze = false}) {
+    final values = _makeValueList(_values.length);
+
+    for (var valueIdx = 0; valueIdx < _values.length; valueIdx += 1) {
+      final value = _values[valueIdx];
+      if (value is PbMap) {
+        values[valueIdx] = value.deepCopy(freeze: freeze);
+      } else if (value is PbList) {
+        values[valueIdx] = value.deepCopy(freeze: freeze);
+      } else if (value is GeneratedMessage) {
+        values[valueIdx] = value.deepCopy(freeze: freeze);
+      } else {
+        values[valueIdx] = value;
+      }
+    }
+
+    final copy = _FieldSet._(
+      message,
+      null, // TODO: event plugin
+      values,
+      null,
+      _unknownFields?.deepCopy(freeze: freeze),
+      freeze, // TODO: Can we use `_frozenState` here?
+      _oneofCases == null ? null : Map.from(_oneofCases!),
+    );
+
+    copy._extensions = _extensions?.deepCopy(copy, freeze: freeze);
+
+    return copy;
+  }
 }

protobuf/lib/src/protobuf/generated_message.dart

@@ -43,11 +43,7 @@ abstract class GeneratedMessage {
   EventPlugin? get eventPlugin => null;
 
   /// Creates a deep copy of the fields in this message.
-  /// (The generated code uses [mergeFromMessage].)
-  @Deprecated('Using this can add significant size overhead to your binary. '
-      'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
-      'Will be removed in next major version')
-  GeneratedMessage clone();
+  GeneratedMessage clone() => deepCopy();
 
   /// Creates an empty instance of the same message type as this.
   ///
@@ -585,5 +581,9 @@ extension GeneratedMessageGenericExtensions<T extends GeneratedMessage> on T {
   }
 
   /// Returns a writable deep copy of this message.
-  T deepCopy() => info_.createEmptyInstance!() as T..mergeFromMessage(this);
+  T deepCopy({bool freeze = false}) {
+    final T message = info_.createEmptyInstance!() as dynamic;
+    message.__fieldSet = __fieldSet?.deepCopy(message, freeze: freeze);
+    return message;
+  }
 }

protobuf/lib/src/protobuf/pb_list.dart

@@ -14,13 +14,14 @@ class PbList<E> extends ListBase<E> {
   final List<E> _wrappedList;
   final CheckFunc<E> _check;
 
-  bool _isReadOnly = false;
+  bool _isReadOnly;
 
   bool get isFrozen => _isReadOnly;
 
   PbList({CheckFunc<E> check = _checkNotNull})
       : _wrappedList = <E>[],
-        _check = check;
+        _check = check,
+        _isReadOnly = false;
 
   PbList.unmodifiable()
       : _wrappedList = const [],
@@ -29,7 +30,10 @@ class PbList<E> extends ListBase<E> {
 
   PbList.from(List from)
       : _wrappedList = List<E>.from(from),
-        _check = _checkNotNull;
+        _check = _checkNotNull,
+        _isReadOnly = false;
+
+  PbList._(this._wrappedList, this._check, this._isReadOnly);
 
   @override
   void add(E element) {
@@ -200,4 +204,26 @@ class PbList<E> extends ListBase<E> {
   static Never _readOnlyError(String methodName) {
     throw UnsupportedError("'$methodName' on a read-only list");
   }
+
+  PbList<E> deepCopy({bool freeze = false}) {
+    // TODO: We know the capacity, is it possible to allocate a list with the right size?
+    final wrappedList = <E>[];
+
+    for (final value in _wrappedList) {
+      // TODO: I'm not sure why I need to cast to dynamic below. If `value : E`
+      // and `value : PbMap`, then `value.deepCopy : E`
+      if (value is PbMap) {
+        wrappedList.add(value.deepCopy(freeze: freeze) as dynamic);
+      } else if (value is PbList) {
+        wrappedList.add(value.deepCopy(freeze: freeze) as dynamic);
+      } else if (value is GeneratedMessage) {
+        final GeneratedMessage message = value;
+        wrappedList.add(message.deepCopy(freeze: freeze) as dynamic);
+      } else {
+        wrappedList.add(value);
+      }
+    }
+
+    return PbList._(wrappedList, _check, freeze);
+  }
 }

protobuf/lib/src/protobuf/pb_map.dart

@@ -33,6 +33,9 @@ class PbMap<K, V> extends MapBase<K, V> {
         _wrappedMap = Map.unmodifiable(other._wrappedMap),
         _isReadonly = true;
 
+  PbMap._(this.keyFieldType, this.valueFieldType, this._wrappedMap,
+      this._isReadonly);
+
   @override
   V? operator [](Object? key) => _wrappedMap[key];
 
@@ -119,4 +122,26 @@ class PbMap<K, V> extends MapBase<K, V> {
     }
     return this;
   }
+
+  PbMap<K, V> deepCopy({bool freeze = false}) {
+    final wrappedMap = <K, V>{};
+
+    for (final entry in _wrappedMap.entries) {
+      final key = entry.key;
+      final value = entry.value;
+
+      if (value is PbMap) {
+        wrappedMap[key] = value.deepCopy(freeze: freeze) as dynamic;
+      } else if (value is PbList) {
+        wrappedMap[key] = value.deepCopy(freeze: freeze) as dynamic;
+      } else if (value is GeneratedMessage) {
+        final GeneratedMessage message = value;
+        wrappedMap[key] = message.deepCopy(freeze: freeze) as dynamic;
+      } else {
+        wrappedMap[key] = value;
+      }
+    }
+
+    return PbMap._(keyFieldType, valueFieldType, wrappedMap, freeze);
+  }
 }

protobuf/lib/src/protobuf/unknown_field_set.dart

@@ -8,11 +8,15 @@ part of protobuf;
 class UnknownFieldSet {
   static final UnknownFieldSet emptyUnknownFieldSet = UnknownFieldSet()
     .._markReadOnly();
-  final Map<int, UnknownFieldSetField> _fields = <int, UnknownFieldSetField>{};
 
-  UnknownFieldSet();
+  final Map<int, UnknownFieldSetField> _fields;
 
-  UnknownFieldSet._clone(UnknownFieldSet unknownFieldSet) {
+  UnknownFieldSet() : _fields = <int, UnknownFieldSetField>{};
+
+  UnknownFieldSet._(this._fields, this._isReadOnly);
+
+  UnknownFieldSet._clone(UnknownFieldSet unknownFieldSet)
+      : _fields = <int, UnknownFieldSetField>{} {
     mergeFromUnknownFieldSet(unknownFieldSet);
   }
 
@@ -195,15 +199,37 @@ class UnknownFieldSet {
       _throwFrozenMessageModificationError('UnknownFieldSet', methodName);
     }
   }
+
+  UnknownFieldSet deepCopy({bool freeze = false}) {
+    final fields = <int, UnknownFieldSetField>{};
+
+    for (final entry in _fields.entries) {
+      final key = entry.key;
+      final value = entry.value;
+      fields[key] = value.deepCopy(freeze: freeze);
+    }
+
+    return UnknownFieldSet._(fields, freeze);
+  }
 }
 
 /// An unknown field in a [UnknownFieldSet].
 class UnknownFieldSetField {
-  List<List<int>> _lengthDelimited = <List<int>>[];
-  List<Int64> _varints = <Int64>[];
-  List<int> _fixed32s = <int>[];
-  List<Int64> _fixed64s = <Int64>[];
-  List<UnknownFieldSet> _groups = <UnknownFieldSet>[];
+  List<List<int>> _lengthDelimited;
+  List<Int64> _varints;
+  List<int> _fixed32s;
+  List<Int64> _fixed64s;
+  List<UnknownFieldSet> _groups;
+
+  UnknownFieldSetField()
+      : _lengthDelimited = <List<int>>[],
+        _varints = <Int64>[],
+        _fixed32s = <int>[],
+        _fixed64s = <Int64>[],
+        _groups = <UnknownFieldSet>[];
+
+  UnknownFieldSetField._(this._lengthDelimited, this._varints, this._fixed32s,
+      this._fixed64s, this._groups);
 
   List<List<int>> get lengthDelimited => _lengthDelimited;
   List<Int64> get varints => _varints;
@@ -309,4 +335,14 @@ class UnknownFieldSetField {
   void addVarint(Int64 value) {
     varints.add(value);
   }
+
+  UnknownFieldSetField deepCopy({bool freeze = false}) {
+    return UnknownFieldSetField._(
+      _lengthDelimited.map((List<int> e) => List<int>.from(e)).toList(),
+      List.from(_varints),
+      List.from(_fixed32s),
+      List.from(_fixed64s),
+      List.from(_groups.map((e) => e.deepCopy(freeze: freeze))),
+    );
+  }
 }

protoc_plugin/lib/src/generated/dart_options.pb.dart

@@ -44,10 +44,6 @@ class DartMixin extends $pb.GeneratedMessage {
   factory DartMixin.fromJson($core.String i,
           [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
       create()..mergeFromJson(i, r);
-  @$core.Deprecated('Using this can add significant overhead to your binary. '
-      'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
-      'Will be removed in next major version')
-  DartMixin clone() => DartMixin()..mergeFromMessage(this);
   @$core.Deprecated('Using this can add significant overhead to your binary. '
       'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
       'Will be removed in next major version')
@@ -128,10 +124,6 @@ class Imports extends $pb.GeneratedMessage {
   factory Imports.fromJson($core.String i,
           [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
       create()..mergeFromJson(i, r);
-  @$core.Deprecated('Using this can add significant overhead to your binary. '
-      'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
-      'Will be removed in next major version')
-  Imports clone() => Imports()..mergeFromMessage(this);
   @$core.Deprecated('Using this can add significant overhead to your binary. '
       'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
       'Will be removed in next major version')