diff --git a/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_class.mustache b/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_class.mustache
index 0ecfb93f567..a8dc4df18f7 100644
--- a/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_class.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_class.mustache
@@ -141,7 +141,7 @@ class {{{classname}}} {
         {{{name}}}: json[r'{{{baseName}}}'] is List
           ? (json[r'{{{baseName}}}'] as List).map((e) =>
               {{#items.complexType}}
-              {{items.complexType}}.listFromJson(json[r'{{{baseName}}}']){{#required}}{{^isNullable}}!{{/isNullable}}{{#uniqueItems}}.toSet(){{/uniqueItems}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}}
+              {{items.complexType}}.listFromJson(json[r'{{{baseName}}}']){{#uniqueItems}}.toSet(){{/uniqueItems}}
               {{/items.complexType}}
               {{^items.complexType}}
               e == null ? {{#items.isNullable}}null{{/items.isNullable}}{{^items.isNullable}}const  <{{items.items.dataType}}>[]{{/items.isNullable}} : (e as List).cast<{{items.items.dataType}}>()
@@ -150,7 +150,7 @@ class {{{classname}}} {
           :  {{#isNullable}}null{{/isNullable}}{{^isNullable}}const []{{/isNullable}},
             {{/items.isArray}}
             {{^items.isArray}}
-        {{{name}}}: {{{complexType}}}.listFromJson(json[r'{{{baseName}}}']){{#required}}{{^isNullable}}!{{/isNullable}}{{#uniqueItems}}.toSet(){{/uniqueItems}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
+        {{{name}}}: {{{complexType}}}.listFromJson(json[r'{{{baseName}}}']){{#uniqueItems}}.toSet(){{/uniqueItems}},
             {{/items.isArray}}
           {{/isArray}}
           {{^isArray}}
@@ -168,7 +168,7 @@ class {{{classname}}} {
               {{^items.isArray}}
                 {{#items.isMap}}
                   {{#items.complexType}}
-        {{{name}}}: {{items.complexType}}.mapFromJson(json[r'{{{baseName}}}']){{#required}}{{^isNullable}}!{{/isNullable}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
+        {{{name}}}: {{items.complexType}}.mapFromJson(json[r'{{{baseName}}}']),
                   {{/items.complexType}}
                   {{^items.complexType}}
         {{{name}}}: mapCastOfType<String, dynamic>(json, r'{{{baseName}}}'){{#required}}{{^isNullable}}!{{/isNullable}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
@@ -176,7 +176,7 @@ class {{{classname}}} {
                 {{/items.isMap}}
                 {{^items.isMap}}
                   {{#items.complexType}}
-        {{{name}}}: {{{items.complexType}}}.mapFromJson(json[r'{{{baseName}}}'{{#required}}{{^isNullable}}!{{/isNullable}}{{/required}}{{^required}}{{#defaultValue}}]) ?? {{{.}}}{{/defaultValue}}{{/required}},
+        {{{name}}}: {{{items.complexType}}}.mapFromJson(json[r'{{{baseName}}}']),
                   {{/items.complexType}}
                   {{^items.complexType}}
         {{{name}}}: mapCastOfType<String, {{items.dataType}}>(json, r'{{{baseName}}}'){{#required}}{{^isNullable}}!{{/isNullable}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
@@ -197,7 +197,7 @@ class {{{classname}}} {
         {{^complexType}}
           {{#isArray}}
             {{#isEnum}}
-        {{{name}}}: {{{items.datatypeWithEnum}}}.listFromJson(json[r'{{{baseName}}}']){{#required}}{{^isNullable}}!{{/isNullable}}{{#uniqueItems}}.toSet(){{/uniqueItems}}{{/required}}{{^required}}{{#defaultValue}} ?? {{{.}}}{{/defaultValue}}{{/required}},
+        {{{name}}}: {{{items.datatypeWithEnum}}}.listFromJson(json[r'{{{baseName}}}']){{#uniqueItems}}.toSet(){{/uniqueItems}},
             {{/isEnum}}
             {{^isEnum}}
         {{{name}}}: json[r'{{{baseName}}}'] is {{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}
@@ -234,7 +234,7 @@ class {{{classname}}} {
     return null;
   }
 
-  static List<{{{classname}}}>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<{{{classname}}}> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <{{{classname}}}>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -265,12 +265,10 @@ class {{{classname}}} {
   static Map<String, List<{{{classname}}}>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<{{{classname}}}>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = {{{classname}}}.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = {{{classname}}}.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum.mustache b/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum.mustache
index 60dd4f3982a..84217b702b9 100644
--- a/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum.mustache
@@ -28,7 +28,7 @@ class {{{classname}}} {
 
   static {{{classname}}}? fromJson(dynamic value) => {{{classname}}}TypeTransformer().decode(value);
 
-  static List<{{{classname}}}>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<{{{classname}}}> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <{{{classname}}}>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum_inline.mustache b/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum_inline.mustache
index 4eedb4d45cf..1fe4428dcb3 100644
--- a/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum_inline.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/serialization/native/native_enum_inline.mustache
@@ -28,7 +28,7 @@ class {{{enumName}}} {
 
   static {{{enumName}}}? fromJson(dynamic value) => {{{enumName}}}TypeTransformer().decode(value);
 
-  static List<{{{enumName}}}>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<{{{enumName}}}> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <{{{enumName}}}>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/api_response.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/api_response.dart
index 666778ab612..556c7ec4a96 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/api_response.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/api_response.dart
@@ -105,7 +105,7 @@ class ApiResponse {
     return null;
   }
 
-  static List<ApiResponse>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ApiResponse> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ApiResponse>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -136,12 +136,10 @@ class ApiResponse {
   static Map<String, List<ApiResponse>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ApiResponse>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ApiResponse.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ApiResponse.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/category.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/category.dart
index 06f01cc120a..c5f0f4a8d27 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/category.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/category.dart
@@ -88,7 +88,7 @@ class Category {
     return null;
   }
 
-  static List<Category>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Category> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Category>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class Category {
   static Map<String, List<Category>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Category>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Category.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Category.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/order.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/order.dart
index d317b6b411f..0894d4b295c 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/order.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/order.dart
@@ -141,7 +141,7 @@ class Order {
     return null;
   }
 
-  static List<Order>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Order> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Order>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -172,12 +172,10 @@ class Order {
   static Map<String, List<Order>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Order>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Order.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Order.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -214,7 +212,7 @@ class OrderStatusEnum {
 
   static OrderStatusEnum? fromJson(dynamic value) => OrderStatusEnumTypeTransformer().decode(value);
 
-  static List<OrderStatusEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OrderStatusEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OrderStatusEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/pet.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/pet.dart
index 89e862f59ae..53a2d20dcec 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/pet.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/pet.dart
@@ -116,14 +116,14 @@ class Pet {
         photoUrls: json[r'photoUrls'] is List
             ? (json[r'photoUrls'] as List).cast<String>()
             : const [],
-        tags: Tag.listFromJson(json[r'tags']) ?? const [],
+        tags: Tag.listFromJson(json[r'tags']),
         status: PetStatusEnum.fromJson(json[r'status']),
       );
     }
     return null;
   }
 
-  static List<Pet>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Pet> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Pet>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -154,12 +154,10 @@ class Pet {
   static Map<String, List<Pet>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Pet>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Pet.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Pet.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -198,7 +196,7 @@ class PetStatusEnum {
 
   static PetStatusEnum? fromJson(dynamic value) => PetStatusEnumTypeTransformer().decode(value);
 
-  static List<PetStatusEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<PetStatusEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <PetStatusEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/tag.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/tag.dart
index 1fd6d01f16d..bf557b6522a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/tag.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/tag.dart
@@ -88,7 +88,7 @@ class Tag {
     return null;
   }
 
-  static List<Tag>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Tag> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Tag>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class Tag {
   static Map<String, List<Tag>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Tag>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Tag.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Tag.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/user.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/user.dart
index 63fc8e52815..57de27fd405 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/user.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/user.dart
@@ -191,7 +191,7 @@ class User {
     return null;
   }
 
-  static List<User>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<User> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <User>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -222,12 +222,10 @@ class User {
   static Map<String, List<User>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<User>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = User.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = User.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/additional_properties_class.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/additional_properties_class.dart
index 68e479ee4f5..42a70fc7fba 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/additional_properties_class.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/additional_properties_class.dart
@@ -68,7 +68,7 @@ class AdditionalPropertiesClass {
     return null;
   }
 
-  static List<AdditionalPropertiesClass>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<AdditionalPropertiesClass> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <AdditionalPropertiesClass>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -99,12 +99,10 @@ class AdditionalPropertiesClass {
   static Map<String, List<AdditionalPropertiesClass>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<AdditionalPropertiesClass>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = AdditionalPropertiesClass.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = AdditionalPropertiesClass.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/all_of_with_single_ref.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/all_of_with_single_ref.dart
index c21911eeec8..9f43c826b40 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/all_of_with_single_ref.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/all_of_with_single_ref.dart
@@ -88,7 +88,7 @@ class AllOfWithSingleRef {
     return null;
   }
 
-  static List<AllOfWithSingleRef>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<AllOfWithSingleRef> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <AllOfWithSingleRef>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class AllOfWithSingleRef {
   static Map<String, List<AllOfWithSingleRef>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<AllOfWithSingleRef>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = AllOfWithSingleRef.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = AllOfWithSingleRef.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/animal.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/animal.dart
index 2329953a708..0a2cd1bc449 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/animal.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/animal.dart
@@ -68,7 +68,7 @@ class Animal {
     return null;
   }
 
-  static List<Animal>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Animal> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Animal>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -99,12 +99,10 @@ class Animal {
   static Map<String, List<Animal>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Animal>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Animal.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Animal.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/api_response.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/api_response.dart
index 666778ab612..556c7ec4a96 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/api_response.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/api_response.dart
@@ -105,7 +105,7 @@ class ApiResponse {
     return null;
   }
 
-  static List<ApiResponse>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ApiResponse> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ApiResponse>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -136,12 +136,10 @@ class ApiResponse {
   static Map<String, List<ApiResponse>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ApiResponse>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ApiResponse.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ApiResponse.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_array_of_number_only.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_array_of_number_only.dart
index 5127b4ec1b9..6066b348dbb 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_array_of_number_only.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_array_of_number_only.dart
@@ -65,7 +65,7 @@ class ArrayOfArrayOfNumberOnly {
     return null;
   }
 
-  static List<ArrayOfArrayOfNumberOnly>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ArrayOfArrayOfNumberOnly> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ArrayOfArrayOfNumberOnly>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -96,12 +96,10 @@ class ArrayOfArrayOfNumberOnly {
   static Map<String, List<ArrayOfArrayOfNumberOnly>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ArrayOfArrayOfNumberOnly>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ArrayOfArrayOfNumberOnly.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ArrayOfArrayOfNumberOnly.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_number_only.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_number_only.dart
index 321f7c4f40c..65a8d4b14d1 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_number_only.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_of_number_only.dart
@@ -63,7 +63,7 @@ class ArrayOfNumberOnly {
     return null;
   }
 
-  static List<ArrayOfNumberOnly>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ArrayOfNumberOnly> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ArrayOfNumberOnly>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -94,12 +94,10 @@ class ArrayOfNumberOnly {
   static Map<String, List<ArrayOfNumberOnly>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ArrayOfNumberOnly>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ArrayOfNumberOnly.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ArrayOfNumberOnly.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_test.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_test.dart
index fea02b3ae8a..1d4114defe6 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_test.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/array_test.dart
@@ -77,7 +77,7 @@ class ArrayTest {
           :  const [],
         arrayArrayOfModel: json[r'array_array_of_model'] is List
           ? (json[r'array_array_of_model'] as List).map((e) =>
-              ReadOnlyFirst.listFromJson(json[r'array_array_of_model']) ?? const []
+              ReadOnlyFirst.listFromJson(json[r'array_array_of_model'])
             ).toList()
           :  const [],
       );
@@ -85,7 +85,7 @@ class ArrayTest {
     return null;
   }
 
-  static List<ArrayTest>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ArrayTest> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ArrayTest>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -116,12 +116,10 @@ class ArrayTest {
   static Map<String, List<ArrayTest>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ArrayTest>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ArrayTest.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ArrayTest.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/capitalization.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/capitalization.dart
index 838c767d3e9..28c2e9d9c64 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/capitalization.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/capitalization.dart
@@ -157,7 +157,7 @@ class Capitalization {
     return null;
   }
 
-  static List<Capitalization>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Capitalization> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Capitalization>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -188,12 +188,10 @@ class Capitalization {
   static Map<String, List<Capitalization>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Capitalization>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Capitalization.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Capitalization.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat.dart
index 6bfb040ad1c..98d12dd0935 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat.dart
@@ -85,7 +85,7 @@ class Cat {
     return null;
   }
 
-  static List<Cat>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Cat> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Cat>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -116,12 +116,10 @@ class Cat {
   static Map<String, List<Cat>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Cat>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Cat.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Cat.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat_all_of.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat_all_of.dart
index 63ed47e43f2..9d090b4068a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat_all_of.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/cat_all_of.dart
@@ -71,7 +71,7 @@ class CatAllOf {
     return null;
   }
 
-  static List<CatAllOf>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<CatAllOf> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <CatAllOf>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class CatAllOf {
   static Map<String, List<CatAllOf>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<CatAllOf>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = CatAllOf.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = CatAllOf.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/category.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/category.dart
index f0cb75c98ea..3d46deb157a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/category.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/category.dart
@@ -78,7 +78,7 @@ class Category {
     return null;
   }
 
-  static List<Category>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Category> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Category>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -109,12 +109,10 @@ class Category {
   static Map<String, List<Category>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Category>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Category.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Category.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/class_model.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/class_model.dart
index b4398348c58..0308856e250 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/class_model.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/class_model.dart
@@ -71,7 +71,7 @@ class ClassModel {
     return null;
   }
 
-  static List<ClassModel>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ClassModel> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ClassModel>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class ClassModel {
   static Map<String, List<ClassModel>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ClassModel>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ClassModel.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ClassModel.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/deprecated_object.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/deprecated_object.dart
index 6f3ff3dc5f4..facf8aa4911 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/deprecated_object.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/deprecated_object.dart
@@ -71,7 +71,7 @@ class DeprecatedObject {
     return null;
   }
 
-  static List<DeprecatedObject>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<DeprecatedObject> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <DeprecatedObject>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class DeprecatedObject {
   static Map<String, List<DeprecatedObject>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<DeprecatedObject>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = DeprecatedObject.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = DeprecatedObject.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog.dart
index 0375767475a..512f5e4344e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog.dart
@@ -85,7 +85,7 @@ class Dog {
     return null;
   }
 
-  static List<Dog>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Dog> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Dog>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -116,12 +116,10 @@ class Dog {
   static Map<String, List<Dog>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Dog>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Dog.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Dog.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog_all_of.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog_all_of.dart
index ae05b515cfa..5398d4b03fd 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog_all_of.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/dog_all_of.dart
@@ -71,7 +71,7 @@ class DogAllOf {
     return null;
   }
 
-  static List<DogAllOf>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<DogAllOf> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <DogAllOf>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class DogAllOf {
   static Map<String, List<DogAllOf>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<DogAllOf>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = DogAllOf.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = DogAllOf.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_arrays.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_arrays.dart
index 78205e004b2..9f48dc8afec 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_arrays.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_arrays.dart
@@ -66,13 +66,13 @@ class EnumArrays {
 
       return EnumArrays(
         justSymbol: EnumArraysJustSymbolEnum.fromJson(json[r'just_symbol']),
-        arrayEnum: EnumArraysArrayEnumEnum.listFromJson(json[r'array_enum']) ?? const [],
+        arrayEnum: EnumArraysArrayEnumEnum.listFromJson(json[r'array_enum']),
       );
     }
     return null;
   }
 
-  static List<EnumArrays>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumArrays> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumArrays>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -103,12 +103,10 @@ class EnumArrays {
   static Map<String, List<EnumArrays>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<EnumArrays>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = EnumArrays.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = EnumArrays.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -143,7 +141,7 @@ class EnumArraysJustSymbolEnum {
 
   static EnumArraysJustSymbolEnum? fromJson(dynamic value) => EnumArraysJustSymbolEnumTypeTransformer().decode(value);
 
-  static List<EnumArraysJustSymbolEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumArraysJustSymbolEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumArraysJustSymbolEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -217,7 +215,7 @@ class EnumArraysArrayEnumEnum {
 
   static EnumArraysArrayEnumEnum? fromJson(dynamic value) => EnumArraysArrayEnumEnumTypeTransformer().decode(value);
 
-  static List<EnumArraysArrayEnumEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumArraysArrayEnumEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumArraysArrayEnumEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_class.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_class.dart
index eac54fb3576..a8a811e6d92 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_class.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_class.dart
@@ -36,7 +36,7 @@ class EnumClass {
 
   static EnumClass? fromJson(dynamic value) => EnumClassTypeTransformer().decode(value);
 
-  static List<EnumClass>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumClass> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumClass>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_test.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_test.dart
index a51d323672d..a5afdc9ea1e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_test.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/enum_test.dart
@@ -156,7 +156,7 @@ class EnumTest {
     return null;
   }
 
-  static List<EnumTest>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumTest> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumTest>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -187,12 +187,10 @@ class EnumTest {
   static Map<String, List<EnumTest>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<EnumTest>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = EnumTest.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = EnumTest.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -230,7 +228,7 @@ class EnumTestEnumStringEnum {
 
   static EnumTestEnumStringEnum? fromJson(dynamic value) => EnumTestEnumStringEnumTypeTransformer().decode(value);
 
-  static List<EnumTestEnumStringEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumTestEnumStringEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumTestEnumStringEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -307,7 +305,7 @@ class EnumTestEnumStringRequiredEnum {
 
   static EnumTestEnumStringRequiredEnum? fromJson(dynamic value) => EnumTestEnumStringRequiredEnumTypeTransformer().decode(value);
 
-  static List<EnumTestEnumStringRequiredEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumTestEnumStringRequiredEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumTestEnumStringRequiredEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -382,7 +380,7 @@ class EnumTestEnumIntegerEnum {
 
   static EnumTestEnumIntegerEnum? fromJson(dynamic value) => EnumTestEnumIntegerEnumTypeTransformer().decode(value);
 
-  static List<EnumTestEnumIntegerEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumTestEnumIntegerEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumTestEnumIntegerEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -456,7 +454,7 @@ class EnumTestEnumNumberEnum {
 
   static EnumTestEnumNumberEnum? fromJson(dynamic value) => EnumTestEnumNumberEnumTypeTransformer().decode(value);
 
-  static List<EnumTestEnumNumberEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<EnumTestEnumNumberEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <EnumTestEnumNumberEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/file_schema_test_class.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/file_schema_test_class.dart
index 8fe78c1a8f1..73b23874dc1 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/file_schema_test_class.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/file_schema_test_class.dart
@@ -72,13 +72,13 @@ class FileSchemaTestClass {
 
       return FileSchemaTestClass(
         file: ModelFile.fromJson(json[r'file']),
-        files: ModelFile.listFromJson(json[r'files']) ?? const [],
+        files: ModelFile.listFromJson(json[r'files']),
       );
     }
     return null;
   }
 
-  static List<FileSchemaTestClass>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<FileSchemaTestClass> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <FileSchemaTestClass>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -109,12 +109,10 @@ class FileSchemaTestClass {
   static Map<String, List<FileSchemaTestClass>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<FileSchemaTestClass>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = FileSchemaTestClass.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = FileSchemaTestClass.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo.dart
index 758f13c778a..637f700923e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo.dart
@@ -61,7 +61,7 @@ class Foo {
     return null;
   }
 
-  static List<Foo>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Foo> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Foo>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -92,12 +92,10 @@ class Foo {
   static Map<String, List<Foo>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Foo>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Foo.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Foo.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo_get_default_response.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo_get_default_response.dart
index dcdcf7220ac..a50b62d7be9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo_get_default_response.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/foo_get_default_response.dart
@@ -71,7 +71,7 @@ class FooGetDefaultResponse {
     return null;
   }
 
-  static List<FooGetDefaultResponse>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<FooGetDefaultResponse> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <FooGetDefaultResponse>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class FooGetDefaultResponse {
   static Map<String, List<FooGetDefaultResponse>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<FooGetDefaultResponse>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = FooGetDefaultResponse.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = FooGetDefaultResponse.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/format_test.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/format_test.dart
index 9a184cb3912..9bacccfef3d 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/format_test.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/format_test.dart
@@ -300,7 +300,7 @@ class FormatTest {
     return null;
   }
 
-  static List<FormatTest>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<FormatTest> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <FormatTest>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -331,12 +331,10 @@ class FormatTest {
   static Map<String, List<FormatTest>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<FormatTest>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = FormatTest.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = FormatTest.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/has_only_read_only.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/has_only_read_only.dart
index 0950c83518b..4211499352c 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/has_only_read_only.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/has_only_read_only.dart
@@ -88,7 +88,7 @@ class HasOnlyReadOnly {
     return null;
   }
 
-  static List<HasOnlyReadOnly>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<HasOnlyReadOnly> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <HasOnlyReadOnly>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class HasOnlyReadOnly {
   static Map<String, List<HasOnlyReadOnly>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<HasOnlyReadOnly>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = HasOnlyReadOnly.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = HasOnlyReadOnly.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/health_check_result.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/health_check_result.dart
index 4d007539339..c8ce4c0c359 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/health_check_result.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/health_check_result.dart
@@ -65,7 +65,7 @@ class HealthCheckResult {
     return null;
   }
 
-  static List<HealthCheckResult>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<HealthCheckResult> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <HealthCheckResult>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -96,12 +96,10 @@ class HealthCheckResult {
   static Map<String, List<HealthCheckResult>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<HealthCheckResult>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = HealthCheckResult.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = HealthCheckResult.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/map_test.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/map_test.dart
index 8c6c143bb7b..0a66b072278 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/map_test.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/map_test.dart
@@ -82,7 +82,7 @@ class MapTest {
     return null;
   }
 
-  static List<MapTest>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<MapTest> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <MapTest>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -113,12 +113,10 @@ class MapTest {
   static Map<String, List<MapTest>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<MapTest>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = MapTest.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = MapTest.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -153,7 +151,7 @@ class MapTestMapOfEnumStringEnum {
 
   static MapTestMapOfEnumStringEnum? fromJson(dynamic value) => MapTestMapOfEnumStringEnumTypeTransformer().decode(value);
 
-  static List<MapTestMapOfEnumStringEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<MapTestMapOfEnumStringEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <MapTestMapOfEnumStringEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/mixed_properties_and_additional_properties_class.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/mixed_properties_and_additional_properties_class.dart
index 2e938ae1943..dfca68e14dc 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/mixed_properties_and_additional_properties_class.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/mixed_properties_and_additional_properties_class.dart
@@ -89,13 +89,13 @@ class MixedPropertiesAndAdditionalPropertiesClass {
       return MixedPropertiesAndAdditionalPropertiesClass(
         uuid: mapValueOfType<String>(json, r'uuid'),
         dateTime: mapDateTime(json, r'dateTime', ''),
-        map: Animal.mapFromJson(json[r'map']) ?? const {},
+        map: Animal.mapFromJson(json[r'map']),
       );
     }
     return null;
   }
 
-  static List<MixedPropertiesAndAdditionalPropertiesClass>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<MixedPropertiesAndAdditionalPropertiesClass> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <MixedPropertiesAndAdditionalPropertiesClass>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -126,12 +126,10 @@ class MixedPropertiesAndAdditionalPropertiesClass {
   static Map<String, List<MixedPropertiesAndAdditionalPropertiesClass>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<MixedPropertiesAndAdditionalPropertiesClass>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = MixedPropertiesAndAdditionalPropertiesClass.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = MixedPropertiesAndAdditionalPropertiesClass.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model200_response.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model200_response.dart
index 1019d663db2..acaa8220f3e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model200_response.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model200_response.dart
@@ -88,7 +88,7 @@ class Model200Response {
     return null;
   }
 
-  static List<Model200Response>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Model200Response> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Model200Response>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class Model200Response {
   static Map<String, List<Model200Response>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Model200Response>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Model200Response.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Model200Response.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_client.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_client.dart
index aaf943cfc09..9010847ca74 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_client.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_client.dart
@@ -71,7 +71,7 @@ class ModelClient {
     return null;
   }
 
-  static List<ModelClient>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ModelClient> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ModelClient>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class ModelClient {
   static Map<String, List<ModelClient>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ModelClient>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ModelClient.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ModelClient.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_file.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_file.dart
index 1d9ea9ddde3..9b98486ecea 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_file.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_file.dart
@@ -72,7 +72,7 @@ class ModelFile {
     return null;
   }
 
-  static List<ModelFile>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ModelFile> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ModelFile>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -103,12 +103,10 @@ class ModelFile {
   static Map<String, List<ModelFile>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ModelFile>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ModelFile.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ModelFile.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_list.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_list.dart
index 4883a049058..ca6abae44c9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_list.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_list.dart
@@ -71,7 +71,7 @@ class ModelList {
     return null;
   }
 
-  static List<ModelList>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ModelList> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ModelList>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class ModelList {
   static Map<String, List<ModelList>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ModelList>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ModelList.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ModelList.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_return.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_return.dart
index faf127da4bd..087ca4cbfa9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_return.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/model_return.dart
@@ -71,7 +71,7 @@ class ModelReturn {
     return null;
   }
 
-  static List<ModelReturn>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ModelReturn> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ModelReturn>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class ModelReturn {
   static Map<String, List<ModelReturn>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ModelReturn>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ModelReturn.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ModelReturn.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/name.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/name.dart
index e41090c54ca..92e8093a807 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/name.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/name.dart
@@ -112,7 +112,7 @@ class Name {
     return null;
   }
 
-  static List<Name>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Name> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Name>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -143,12 +143,10 @@ class Name {
   static Map<String, List<Name>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Name>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Name.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Name.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/nullable_class.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/nullable_class.dart
index 631f60ab09e..0a5a70afa50 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/nullable_class.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/nullable_class.dart
@@ -169,9 +169,9 @@ class NullableClass {
         stringProp: mapValueOfType<String>(json, r'string_prop'),
         dateProp: mapDateTime(json, r'date_prop', ''),
         datetimeProp: mapDateTime(json, r'datetime_prop', ''),
-        arrayNullableProp: Object.listFromJson(json[r'array_nullable_prop']) ?? const [],
-        arrayAndItemsNullableProp: Object.listFromJson(json[r'array_and_items_nullable_prop']) ?? const [],
-        arrayItemsNullable: Object.listFromJson(json[r'array_items_nullable']) ?? const [],
+        arrayNullableProp: Object.listFromJson(json[r'array_nullable_prop']),
+        arrayAndItemsNullableProp: Object.listFromJson(json[r'array_and_items_nullable_prop']),
+        arrayItemsNullable: Object.listFromJson(json[r'array_items_nullable']),
         objectNullableProp: mapCastOfType<String, Object>(json, r'object_nullable_prop') ?? const {},
         objectAndItemsNullableProp: mapCastOfType<String, Object>(json, r'object_and_items_nullable_prop') ?? const {},
         objectItemsNullable: mapCastOfType<String, Object>(json, r'object_items_nullable') ?? const {},
@@ -180,7 +180,7 @@ class NullableClass {
     return null;
   }
 
-  static List<NullableClass>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<NullableClass> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <NullableClass>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -211,12 +211,10 @@ class NullableClass {
   static Map<String, List<NullableClass>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<NullableClass>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = NullableClass.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = NullableClass.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/number_only.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/number_only.dart
index 387397e6e4e..405f9f326b8 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/number_only.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/number_only.dart
@@ -73,7 +73,7 @@ class NumberOnly {
     return null;
   }
 
-  static List<NumberOnly>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<NumberOnly> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <NumberOnly>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -104,12 +104,10 @@ class NumberOnly {
   static Map<String, List<NumberOnly>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<NumberOnly>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = NumberOnly.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = NumberOnly.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/object_with_deprecated_fields.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/object_with_deprecated_fields.dart
index 36b0fee3d78..2e2e2b7c687 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/object_with_deprecated_fields.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/object_with_deprecated_fields.dart
@@ -116,7 +116,7 @@ class ObjectWithDeprecatedFields {
     return null;
   }
 
-  static List<ObjectWithDeprecatedFields>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ObjectWithDeprecatedFields> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ObjectWithDeprecatedFields>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -147,12 +147,10 @@ class ObjectWithDeprecatedFields {
   static Map<String, List<ObjectWithDeprecatedFields>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ObjectWithDeprecatedFields>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ObjectWithDeprecatedFields.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ObjectWithDeprecatedFields.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/order.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/order.dart
index d317b6b411f..0894d4b295c 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/order.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/order.dart
@@ -141,7 +141,7 @@ class Order {
     return null;
   }
 
-  static List<Order>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Order> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Order>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -172,12 +172,10 @@ class Order {
   static Map<String, List<Order>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Order>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Order.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Order.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -214,7 +212,7 @@ class OrderStatusEnum {
 
   static OrderStatusEnum? fromJson(dynamic value) => OrderStatusEnumTypeTransformer().decode(value);
 
-  static List<OrderStatusEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OrderStatusEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OrderStatusEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_composite.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_composite.dart
index 6898564d6fd..f0e549abf66 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_composite.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_composite.dart
@@ -107,7 +107,7 @@ class OuterComposite {
     return null;
   }
 
-  static List<OuterComposite>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OuterComposite> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OuterComposite>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -138,12 +138,10 @@ class OuterComposite {
   static Map<String, List<OuterComposite>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<OuterComposite>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = OuterComposite.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = OuterComposite.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum.dart
index 9b4da615064..61e17c3bde9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum.dart
@@ -36,7 +36,7 @@ class OuterEnum {
 
   static OuterEnum? fromJson(dynamic value) => OuterEnumTypeTransformer().decode(value);
 
-  static List<OuterEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OuterEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OuterEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_default_value.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_default_value.dart
index 7b6061f4937..cbbcc7597c6 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_default_value.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_default_value.dart
@@ -36,7 +36,7 @@ class OuterEnumDefaultValue {
 
   static OuterEnumDefaultValue? fromJson(dynamic value) => OuterEnumDefaultValueTypeTransformer().decode(value);
 
-  static List<OuterEnumDefaultValue>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OuterEnumDefaultValue> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OuterEnumDefaultValue>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer.dart
index eebb241e551..d9583ad84c6 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer.dart
@@ -36,7 +36,7 @@ class OuterEnumInteger {
 
   static OuterEnumInteger? fromJson(dynamic value) => OuterEnumIntegerTypeTransformer().decode(value);
 
-  static List<OuterEnumInteger>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OuterEnumInteger> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OuterEnumInteger>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer_default_value.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer_default_value.dart
index f1b26dedd8f..a62d9b7ecd9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer_default_value.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_enum_integer_default_value.dart
@@ -36,7 +36,7 @@ class OuterEnumIntegerDefaultValue {
 
   static OuterEnumIntegerDefaultValue? fromJson(dynamic value) => OuterEnumIntegerDefaultValueTypeTransformer().decode(value);
 
-  static List<OuterEnumIntegerDefaultValue>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OuterEnumIntegerDefaultValue> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OuterEnumIntegerDefaultValue>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_object_with_enum_property.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_object_with_enum_property.dart
index 04177475ea3..44aecf1a295 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_object_with_enum_property.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/outer_object_with_enum_property.dart
@@ -61,7 +61,7 @@ class OuterObjectWithEnumProperty {
     return null;
   }
 
-  static List<OuterObjectWithEnumProperty>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<OuterObjectWithEnumProperty> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <OuterObjectWithEnumProperty>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -92,12 +92,10 @@ class OuterObjectWithEnumProperty {
   static Map<String, List<OuterObjectWithEnumProperty>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<OuterObjectWithEnumProperty>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = OuterObjectWithEnumProperty.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = OuterObjectWithEnumProperty.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/pet.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/pet.dart
index a00ec5e3941..669bf85edd5 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/pet.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/pet.dart
@@ -116,14 +116,14 @@ class Pet {
         photoUrls: json[r'photoUrls'] is Set
             ? (json[r'photoUrls'] as Set).cast<String>()
             : const {},
-        tags: Tag.listFromJson(json[r'tags']) ?? const [],
+        tags: Tag.listFromJson(json[r'tags']),
         status: PetStatusEnum.fromJson(json[r'status']),
       );
     }
     return null;
   }
 
-  static List<Pet>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Pet> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Pet>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -154,12 +154,10 @@ class Pet {
   static Map<String, List<Pet>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Pet>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Pet.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Pet.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
@@ -198,7 +196,7 @@ class PetStatusEnum {
 
   static PetStatusEnum? fromJson(dynamic value) => PetStatusEnumTypeTransformer().decode(value);
 
-  static List<PetStatusEnum>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<PetStatusEnum> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <PetStatusEnum>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/read_only_first.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/read_only_first.dart
index 3599aff10a8..e266da48745 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/read_only_first.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/read_only_first.dart
@@ -88,7 +88,7 @@ class ReadOnlyFirst {
     return null;
   }
 
-  static List<ReadOnlyFirst>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<ReadOnlyFirst> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <ReadOnlyFirst>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class ReadOnlyFirst {
   static Map<String, List<ReadOnlyFirst>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<ReadOnlyFirst>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = ReadOnlyFirst.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = ReadOnlyFirst.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/single_ref_type.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/single_ref_type.dart
index a4f17af4d5f..f750f7ff7de 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/single_ref_type.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/single_ref_type.dart
@@ -34,7 +34,7 @@ class SingleRefType {
 
   static SingleRefType? fromJson(dynamic value) => SingleRefTypeTypeTransformer().decode(value);
 
-  static List<SingleRefType>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<SingleRefType> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <SingleRefType>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/special_model_name.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/special_model_name.dart
index f92b8d67d7a..5d745143dcc 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/special_model_name.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/special_model_name.dart
@@ -71,7 +71,7 @@ class SpecialModelName {
     return null;
   }
 
-  static List<SpecialModelName>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<SpecialModelName> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <SpecialModelName>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -102,12 +102,10 @@ class SpecialModelName {
   static Map<String, List<SpecialModelName>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<SpecialModelName>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = SpecialModelName.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = SpecialModelName.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/tag.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/tag.dart
index 1fd6d01f16d..bf557b6522a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/tag.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/tag.dart
@@ -88,7 +88,7 @@ class Tag {
     return null;
   }
 
-  static List<Tag>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<Tag> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <Tag>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -119,12 +119,10 @@ class Tag {
   static Map<String, List<Tag>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<Tag>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = Tag.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = Tag.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/user.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/user.dart
index 63fc8e52815..57de27fd405 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/user.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/model/user.dart
@@ -191,7 +191,7 @@ class User {
     return null;
   }
 
-  static List<User>? listFromJson(dynamic json, {bool growable = false,}) {
+  static List<User> listFromJson(dynamic json, {bool growable = false,}) {
     final result = <User>[];
     if (json is List && json.isNotEmpty) {
       for (final row in json) {
@@ -222,12 +222,10 @@ class User {
   static Map<String, List<User>> mapListFromJson(dynamic json, {bool growable = false,}) {
     final map = <String, List<User>>{};
     if (json is Map && json.isNotEmpty) {
-      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
       for (final entry in json.entries) {
-        final value = User.listFromJson(entry.value, growable: growable,);
-        if (value != null) {
-          map[entry.key] = value;
-        }
+        map[entry.key] = User.listFromJson(entry.value, growable: growable,);
       }
     }
     return map;