added _defaults

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

@@ -404,6 +404,7 @@ private void syncRootTypesWithInnerVars(Map<String, CodegenModel> objs, CodegenM
     private final String kHasAncestorOnlyProps = "x-has-ancestor-only-props";
     private final String kSelfAndAncestorOnlyProps = "x-self-and-ancestor-only-props";
     private final String kHasSelfAndAncestorOnlyProps = "x-has-self-and-ancestor-only-props";
+    private final String kParentDiscriminator = "x-parent-discriminator";
 
     // adapts codegen models and property to dart rules of inheritance
     private void adaptToDartInheritance(Map<String, ModelsMap> objs) {
@@ -455,7 +456,11 @@ private void adaptToDartInheritance(Map<String, ModelsMap> objs) {
             cm.vendorExtensions.put(kIsPure, isPure);
             if (!isParent && (cm.oneOf == null || cm.oneOf.isEmpty()) && (cm.anyOf == null || cm.anyOf.isEmpty())) {
                 //discriminator has no meaning here
-                cm.discriminator=null;
+                if (cm.discriminator!=null) {
+                    cm.vendorExtensions.put(kParentDiscriminator, cm.discriminator);
+                    cm.discriminator=null;
+                }
+
             }
             // when pure:
             // vars = allVars = selfOnlyProperties = kSelfAndAncestorOnlyProps

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

@@ -11,16 +11,8 @@ part '{{classFilename}}.g.dart';
 {{>serialization/built_value/class_members}}
 }
 {{#discriminator}}{{#hasDiscriminatorWithNonEmptyMapping}}
-extension {{classname}}DiscriminatorExt on {{classname}} {
-    String? discriminatorValue() {
-        {{#mappedModels}}
-        if (this is {{modelName}}) {
-        return r'{{mappingName}}';
-        }
-        {{/mappedModels}}
-        return null;
-    }
-}{{/hasDiscriminatorWithNonEmptyMapping}}{{/discriminator}}
+{{>serialization/built_value/class_discriminator}}
+{{/hasDiscriminatorWithNonEmptyMapping}}{{/discriminator}}
 {{>serialization/built_value/class_serializer}}{{#vendorExtensions.x-is-parent}}
 
 {{>serialization/built_value/class_concrete}}{{/vendorExtensions.x-is-parent}}

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

@@ -0,0 +1,20 @@
+extension {{classname}}DiscriminatorExt on {{classname}} {
+    String? discriminatorValue() {
+        {{#mappedModels}}
+        if (this is {{modelName}}) {
+            return r'{{mappingName}}';
+        }
+        {{/mappedModels}}
+        return null;
+    }
+}
+extension {{classname}}BuilderDiscriminatorExt on {{classname}}Builder {
+    String? discriminatorValue() {
+        {{#mappedModels}}
+        if (this is {{modelName}}Builder) {
+            return r'{{mappingName}}';
+        }
+        {{/mappedModels}}
+        return null;
+    }
+}

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

@@ -28,7 +28,7 @@
   factory {{classname}}([void updates({{classname}}Builder b)]) = _${{classname}};
 
   @BuiltValueHook(initializeBuilder: true)
-  static void _defaults({{{classname}}}Builder b) => b{{#vendorExtensions.x-self-and-ancestor-only-props}}{{#defaultValue}}
+  static void _defaults({{{classname}}}Builder b) => b{{#vendorExtensions.x-parent-discriminator}}..{{propertyName}}=b.discriminatorValue(){{/vendorExtensions.x-parent-discriminator}}{{#vendorExtensions.x-self-and-ancestor-only-props}}{{#defaultValue}}
       ..{{{name}}} = {{#isEnum}}{{^isContainer}}const {{{enumName}}}._({{/isContainer}}{{/isEnum}}{{{defaultValue}}}{{#isEnum}}{{^isContainer}}){{/isContainer}}{{/isEnum}}{{/defaultValue}}{{/vendorExtensions.x-self-and-ancestor-only-props}};
 
 {{/vendorExtensions.x-is-parent}}  @BuiltValueSerializer(custom: true)

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

@@ -10,26 +10,17 @@ class _${{classname}}Serializer implements PrimitiveSerializer<{{classname}}> {
     {{{classname}}} object, {
     FullType specifiedType = FullType.unspecified,
   }) sync* {
-    {{#vendorExtensions.x-self-and-ancestor-only-props}}
-    {{#required}}
-    {{!
-        A required property need to always be part of the serialized output.
-        When it is nullable, null is serialized, otherwise it is an error if it is null.
-    }}
-    yield r'{{baseName}}';
-    yield {{#isNullable}}object.{{{name}}} == null ? null : {{/isNullable}}serializers.serialize(
-      object.{{{name}}},
-      specifiedType: const {{>serialization/built_value/variable_serializer_type}},
-    );
-    {{/required}}
+    {{#vendorExtensions.x-self-and-ancestor-only-props}}    
+    {{! Non-required properties are only serialized if not null. }}
     {{^required}}
     if (object.{{{name}}} != null) {
-      {{! Non-required properties are only serialized if not null. }}
+    {{/required}}
       yield r'{{baseName}}';
-      yield serializers.serialize(
+      yield {{#required}}{{#isNullable}}object.{{{name}}} == null ? null : {{/isNullable}}{{/required}}serializers.serialize(
         object.{{{name}}},
         specifiedType: const {{>serialization/built_value/variable_serializer_type}},
       );
+    {{^required}}
     }
     {{/required}}
     {{/vendorExtensions.x-self-and-ancestor-only-props}}