Replaces isNullable with isOptional.

Signed-off-by: Chito <[email protected]>

Author: chitochi

protoc_plugin/lib/src/message_generator.dart

@@ -554,7 +554,7 @@ class MessageGenerator extends ProtobufContainer {
       out.println(commentBlock);
     }
 
-    if (useNullable && field.isNullable) {
+    if (useNullable && field.isOptional) {
       fieldTypeString += '?';
     }
 
@@ -567,7 +567,7 @@ class MessageGenerator extends ProtobufContainer {
         defaultExpr,
         field.isRepeated,
         field.isMapField,
-        useNullable && field.isNullable);
+        useNullable && field.isOptional);
 
     out.printlnAnnotated(
         '$fieldTypeString get ${names!.fieldName} => $getterExpr;', [
@@ -596,7 +596,7 @@ class MessageGenerator extends ProtobufContainer {
       _emitOverrideIf(field.overridesSetter, out);
       _emitIndexAnnotation(field.number, out);
       if (fastSetter != null) {
-        if (useNullable && field.isNullable) {
+        if (useNullable && field.isOptional) {
           fastSetter += 'Nullable';
         }
         out.printlnAnnotated(
@@ -612,7 +612,7 @@ class MessageGenerator extends ProtobufContainer {
             ]);
       } else {
         final setterName =
-            useNullable && field.isNullable ? '\$_setFieldNullable' : '\$_setField';
+            useNullable && field.isOptional ? '\$_setFieldNullable' : '\$_setField';
 
         out.printlnAnnotated(
             'set ${names.fieldName}'

protoc_plugin/lib/src/protobuf_field.dart

@@ -65,6 +65,12 @@ class ProtobufField {
   bool get isRepeated =>
       descriptor.label == FieldDescriptorProto_Label.LABEL_REPEATED;
 
+  bool get isOptional {
+    if (isRepeated) return false;
+    if (isRequired || !descriptor.proto3Optional) return false;
+    return true;
+  }
+
   /// Whether a numeric field is repeated and must be encoded with packed
   /// encoding.
   ///
@@ -140,12 +146,6 @@ class ProtobufField {
     // for example in package:protobuf/src/protobuf/mixins/well_known.dart.
   }
 
-  bool get isNullable {
-    if (isRepeated) return false;
-    if (isRequired) return false;
-    return descriptor.proto3Optional || baseType.isMessage;
-  }
-
   /// Returns the expression to use for the Dart type.
   String getDartType() {
     if (isMapField) {