Library changes (initialized extension)

csharp/src/Google.Protobuf/Collections/MapField.cs

@@ -285,14 +285,6 @@ public void Clear()
             map.Clear();
         }
 
-        /// <summary>
-        /// Determines whether all map message values are initialized
-        /// </summary>
-        public bool IsInitialized()
-        {
-            return list.All(kvp => kvp.Value is IMessage2 message ? message.IsInitialized() : true);
-        }
-
         /// <summary>
         /// Determines whether map contains an entry equivalent to the given key/value pair.
         /// </summary>

csharp/src/Google.Protobuf/Collections/RepeatedField.cs

@@ -292,28 +292,6 @@ public bool Remove(T item)
         /// </summary>
         public bool IsReadOnly => false;
 
-        /// <summary>
-        /// Gets a value indicating whether the elements in the collection are all initialized
-        /// </summary>
-        public bool IsInitialized()
-        {
-            for (int i = 0; i < count; i++)
-            {
-                T value = array[i];
-                if (value is IMessage2 message)
-                {
-                    if (!message.IsInitialized())
-                        return false;
-                }
-                else
-                {
-                    return true;
-                }
-            }
-
-            return true;
-        }
-
         /// <summary>
         /// Adds all of the specified values into this collection.
         /// </summary>

csharp/src/Google.Protobuf/IMessage.cs

@@ -69,18 +69,6 @@ public interface IMessage
         MessageDescriptor Descriptor { get; }
     }
 
-    /// <summary>
-    /// Interface for a Protocol Buffers message, supporting 
-    /// proto2 operations required for serialization
-    /// </summary>
-    public interface IMessage2 : IMessage
-    {
-        /// <summary>
-        /// Checks if all required fields have values set
-        /// </summary>
-        bool IsInitialized();
-    }
-
     /// <summary>
     /// Generic interface for a Protocol Buffers message,
     /// where the type parameter is expected to be the same type as

csharp/src/Google.Protobuf/MessageExtensions.cs

@@ -30,7 +30,10 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endregion
 
+using Google.Protobuf.Reflection;
+using System.Collections;
 using System.IO;
+using System.Linq;
 
 namespace Google.Protobuf
 {
@@ -140,6 +143,75 @@ public static ByteString ToByteString(this IMessage message)
             return ByteString.AttachBytes(message.ToByteArray());
         }
 
+        /// <summary>
+        /// Checks if all required fields in a message have values set. For proto3 messages, this returns true
+        /// </summary>
+        public static bool IsInitialized(this IMessage message)
+        {
+            if (message.Descriptor.File.Proto.Syntax != "proto2")
+            {
+                return true;
+            }
+
+            return message.Descriptor
+                .Fields
+                .InDeclarationOrder()
+                .Where(f => f.IsRequired || f.IsRepeated || f.IsMap || f.MessageType != null)
+                .All(f =>
+                {
+                    if (f.MessageType != null)
+                    {
+                        if (f.Accessor.HasValue(message))
+                        {
+                            var field = (IMessage)f.Accessor.GetValue(message);
+                            return field.IsInitialized();
+                        }
+                        else
+                        {
+                            return false;
+                        }
+                    }
+                    else if (f.IsRepeated)
+                    {
+                        IList list = (IList)f.Accessor.GetValue(message);
+                        foreach (IMessage item in list)
+                        {
+                            if (item is null)
+                            {
+                                return true;
+                            }
+                            else if (!item.IsInitialized())
+                            {
+                                return false;
+                            }
+                        }
+
+                        return true;
+                    }
+                    else if (f.IsMap)
+                    {
+                        IDictionary list = (IDictionary)f.Accessor.GetValue(message);
+                        foreach (IMessage item in list.Values)
+                        {
+                            if (item is null)
+                            {
+                                return true;
+                            }
+                            else if (!item.IsInitialized())
+                            {
+                                return false;
+                            }
+                        }
+
+                        return true;
+                    }
+                    else
+                    {
+                        return f.Accessor.HasValue(message);
+                    }
+                });
+        }
+
         // Implementations allowing unknown fields to be discarded.
         internal static void MergeFrom(this IMessage message, byte[] data, bool discardUnknownFields)
         {

csharp/src/Google.Protobuf/MessageParser.cs

@@ -175,7 +175,7 @@ internal void MergeFrom(IMessage message, CodedInputStream codedInput)
 
         internal static void CheckMergedRequiredFields(IMessage message)
         {
-            if (message is IMessage2 proto2 && !proto2.IsInitialized())
+            if (!message.IsInitialized())
                 throw new InvalidOperationException("Parsed message does not contain all required fields");
         }
 

csharp/src/Google.Protobuf/Reflection/FieldDescriptor.cs

@@ -183,6 +183,11 @@ private static FieldType GetFieldTypeFromProtoType(FieldDescriptorProto.Types.Ty
         /// </summary>
         public bool IsRepeated => Proto.Label == FieldDescriptorProto.Types.Label.Repeated;
 
+        /// <summary>
+        /// Returns <c>true</c> if this field is a required field; <c>false</c> otherwise.
+        /// </summary>
+        public bool IsRequired => Proto.Label == FieldDescriptorProto.Types.Label.Required;
+
         /// <summary>
         /// Returns <c>true</c> if this field is a map field; <c>false</c> otherwise.
         /// </summary>

csharp/src/Google.Protobuf/Reflection/IFieldAccessor.cs

@@ -52,7 +52,7 @@ public interface IFieldAccessor
         void Clear(IMessage message);
 
         /// <summary>
-        /// Indicates whether the field in the specified message is set. For proto3 fields and repeated fields, this throws an <see cref="InvalidOperationException"/>
+        /// Indicates whether the field in the specified message is set. For proto3 fields, this throws an <see cref="InvalidOperationException"/>
         /// </summary>
         bool HasValue(IMessage message);
 

csharp/src/Google.Protobuf/Reflection/RepeatedFieldAccessor.cs

@@ -53,7 +53,7 @@ public override void Clear(IMessage message)
 
         public override bool HasValue(IMessage message)
         {
-            throw new NotImplementedException();
+            throw new InvalidOperationException("HasValue is not implemented for repeated fields");
         }
 
         public override void SetValue(IMessage message, object value)