fix: more testings which ended up actually needing the deserialization part

Author: radelcom

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractDartCodegen.java

@@ -657,13 +657,16 @@ private void wrapPropertyWithOptional(CodegenProperty property) {
 
         boolean hasNullableSuffix = property.dataType.endsWith("?");
         String baseType = hasNullableSuffix ? property.dataType.substring(0, property.dataType.length() - 1) : property.dataType;
+        property.vendorExtensions.put("x-unwrapped-datatype-nullable", baseType + "?");
         property.dataType = "Optional<" + baseType + "?" + ">";
 
         if (property.datatypeWithEnum != null && !property.datatypeWithEnum.startsWith("Optional<")) {
             hasNullableSuffix = property.datatypeWithEnum.endsWith("?");
             baseType = hasNullableSuffix ? property.datatypeWithEnum.substring(0, property.datatypeWithEnum.length() - 1) : property.datatypeWithEnum;
             property.datatypeWithEnum = "Optional<" + baseType + "?" + ">";
         }
+
+        property.isNullable = false;
     }
 
     @Override

modules/openapi-generator/src/main/resources/dart/libraries/dio/optional.mustache

@@ -19,7 +19,7 @@ import 'package:json_annotation/json_annotation.dart';
 /// // Field has value - sends {"field": "value"}
 /// final patch3 = Model(field: const Optional.present('value'));
 /// ```
-sealed class Optional<T> {
+abstract class Optional<T> {
   const Optional();
 
   /// Creates an Optional with an absent value (not set).
@@ -48,7 +48,7 @@ sealed class Optional<T> {
 }
 
 /// Represents an absent Optional value.
-final class Absent<T> extends Optional<T> {
+class Absent<T> extends Optional<T> {
   const Absent();
 
   @override
@@ -77,7 +77,7 @@ final class Absent<T> extends Optional<T> {
 }
 
 /// Represents a present Optional value.
-final class Present<T> extends Optional<T> {
+class Present<T> extends Optional<T> {
   const Present(this._value);
 
   final T _value;

modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/built_value/class_members.mustache

@@ -7,7 +7,7 @@
   @Deprecated('{{{name}}} has been deprecated')
   {{/deprecated}}
   @BuiltValueField(wireName: r'{{baseName}}')
-  {{>serialization/built_value/variable_type}}{{^isNullable}}{{^required}}?{{/required}}{{/isNullable}} get {{name}};
+  {{>serialization/built_value/variable_type}}{{^vendorExtensions.x-is-optional}}{{^isNullable}}{{^required}}?{{/required}}{{/isNullable}}{{/vendorExtensions.x-is-optional}} get {{name}};
   {{#allowableValues}}
   // {{#min}}range from {{{min}}} to {{{max}}}{{/min}}{{^min}}enum {{name}}Enum { {{#values}} {{{.}}}, {{/values}} };{{/min}}
   {{/allowableValues}}

modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/built_value/deserialize_properties.mustache

@@ -12,6 +12,14 @@
       switch (key) {
         {{#vendorExtensions.x-self-and-ancestor-only-props}}
         case r'{{baseName}}':
+          {{#vendorExtensions.x-is-optional}}
+          final valueDes = serializers.deserialize(
+            value,
+            specifiedType: const {{>serialization/built_value/variable_serializer_type}},
+          ) as {{{vendorExtensions.x-unwrapped-datatype-nullable}}};
+          result.{{{name}}} = Optional.present(valueDes);
+          {{/vendorExtensions.x-is-optional}}
+          {{^vendorExtensions.x-is-optional}}
           final valueDes = serializers.deserialize(
             value,
             specifiedType: const {{>serialization/built_value/variable_serializer_type}},
@@ -46,6 +54,7 @@
           {{/isModel}}
           {{/isEnum}}
           {{/isContainer}}
+          {{/vendorExtensions.x-is-optional}}
           break;
         {{/vendorExtensions.x-self-and-ancestor-only-props}}
         default: