Fix handling of map fields inheriting DELIMITED

Author: mkruskal-google

Makefile

@@ -353,6 +353,7 @@ regenerate-fuzz-protos: build ${PROTOC_GEN_SWIFT}
 SWIFT_PLUGINLIB_DESCRIPTOR_TEST_PROTOS= \
 	Protos/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test.proto \
 	Protos/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_test2.proto \
+	Protos/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_delimited.proto \
 	Protos/SwiftProtobufPluginLibraryTests/google/protobuf/unittest_delimited.proto \
 	Protos/SwiftProtobufPluginLibraryTests/google/protobuf/unittest_delimited_import.proto \
 	Protos/SwiftProtobufPluginLibrary/google/protobuf/compiler/plugin.proto \

Protos/SwiftProtobufPluginLibraryTests/pluginlib_descriptor_delimited.proto

@@ -0,0 +1,31 @@
+// Protos/pluginlib_descriptor_test.proto - test proto
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2024 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+// -----------------------------------------------------------------------------
+///
+/// Test proto for Tests/SwiftProtobufPluginLibraryTests/Test_Descriptor.swift
+///
+// -----------------------------------------------------------------------------
+
+edition = "2023";
+
+package swift_descriptor_test;
+
+option features.message_encoding = DELIMITED;
+
+message EditionsMessageForDelimited {
+  int32 scalar_field = 1;
+  map<int32, string> map_field = 2;
+  map<int32, EditionsMessageForDelimited> message_map_field = 3;
+  EditionsMessageForDelimited delimited_field = 4;
+  EditionsMessageForDelimited length_prefixed_field = 5 [
+    features.message_encoding = LENGTH_PREFIXED
+  ];
+}

Sources/SwiftProtobufPluginLibrary/Descriptor.swift

@@ -791,7 +791,9 @@ public final class FieldDescriptor {
   static let kLastReservedNumber: Int = 19999
 
   /// Declared type of this field.
-  public let type: Google_Protobuf_FieldDescriptorProto.TypeEnum
+  public var type: Google_Protobuf_FieldDescriptorProto.TypeEnum { return _type }
+  private var _type: Google_Protobuf_FieldDescriptorProto.TypeEnum
+
   /// optional/required/repeated
   public let label: Google_Protobuf_FieldDescriptorProto.Label
 
@@ -1001,9 +1003,9 @@ public final class FieldDescriptor {
     // help ensure basic transforms from .proto2 to .edition2023 generate the
     // same code/behaviors.
     if proto.type == .message && self.features.messageEncoding == .delimited {
-      self.type = .group
+      self._type = .group
     } else {
-      self.type = proto.type
+      self._type = proto.type
     }
     // This remapping is based follow part of what upstream
     // `DescriptorBuilder::PostProcessFieldFeatures()` does. If generators use
@@ -1046,7 +1048,14 @@ public final class FieldDescriptor {
       if type == .enum {
         _fieldTypeStorage = .enum(UnownedBox(value: registry.enumDescriptor(named: typeName)!))
       } else {
-        _fieldTypeStorage = .message(UnownedBox(value: registry.descriptor(named: typeName)!))
+        let msgtype = registry.descriptor(named: typeName)!
+        _fieldTypeStorage = .message(UnownedBox(value: msgtype))
+        if type == .group && (
+          msgtype.options.mapEntry ||
+          (_containingType != nil && _containingType!.options.mapEntry)
+        ) {
+          _type = .message
+        }
       }
     }
   }