allow a message field to be unset

ruby/ext/google/protobuf_c/storage.c

@@ -155,7 +155,9 @@ void native_slot_set_value_and_case(upb_fieldtype_t type, VALUE type_class,
       break;
     }
     case UPB_TYPE_MESSAGE: {
-      if (CLASS_OF(value) != type_class) {
+      if (CLASS_OF(value) == CLASS_OF(Qnil)) {
+        value = Qnil;
+      } else if (CLASS_OF(value) != type_class) {
         rb_raise(rb_eTypeError,
                  "Invalid type %s to assign to submessage field.",
                  rb_class2name(CLASS_OF(value)));

ruby/pom.xml

@@ -78,7 +78,7 @@
         <dependency>
             <groupId>com.google.protobuf</groupId>
             <artifactId>protobuf-java</artifactId>
-            <version>3.0.0-pre</version>
+            <version>3.0.0-alpha-3-pre</version>
         </dependency>
     </dependencies>
 </project>

ruby/src/main/java/com/google/protobuf/jruby/RubyMessage.java

@@ -659,14 +659,14 @@ public class RubyMessage extends RubyObject {
             } else {
                 Descriptors.FieldDescriptor.Type fieldType = fieldDescriptor.getType();
                 IRubyObject typeClass = context.runtime.getObject();
+                boolean addValue = true;
                 if (fieldType == Descriptors.FieldDescriptor.Type.MESSAGE) {
                     typeClass = ((RubyDescriptor) getDescriptorForField(context, fieldDescriptor)).msgclass(context);
+                    if (value.isNil()){
+                        addValue = false;
+                    }
                 } else if (fieldType == Descriptors.FieldDescriptor.Type.ENUM) {
                     typeClass = ((RubyEnumDescriptor) getDescriptorForField(context, fieldDescriptor)).enummodule(context);
-                }
-                Utils.checkType(context, fieldType, value, (RubyModule) typeClass);
-                // Convert integer enum to symbol
-                if (fieldType == Descriptors.FieldDescriptor.Type.ENUM) {
                     Descriptors.EnumDescriptor enumDescriptor = fieldDescriptor.getEnumType();
                     if (Utils.isRubyNum(value)) {
                         Descriptors.EnumValueDescriptor val =
@@ -674,7 +674,12 @@ public class RubyMessage extends RubyObject {
                         if (val.getIndex() != -1) value = context.runtime.newSymbol(val.getName());
                     }
                 }
+                if (addValue) {
+                    Utils.checkType(context, fieldType, value, (RubyModule) typeClass);
                     this.fields.put(fieldDescriptor, value);
+                } else {
+                    this.fields.remove(fieldDescriptor);
+                }
             }
         }
         return context.runtime.getNil();

ruby/tests/basic.rb

@@ -154,6 +154,8 @@ module BasicTest
       assert m.optional_bytes == "world"
       m.optional_msg = TestMessage2.new(:foo => 42)
       assert m.optional_msg == TestMessage2.new(:foo => 42)
+      m.optional_msg = nil
+      assert m.optional_msg == nil
     end
 
     def test_ctor_args