[BUG][DART] Fix anyOf undeclared enum, empty class syntax, and nested map cast

Three bugs in the dart generator surfaced from the same end-user spec.
The repros are added to the dart fake-petstore yaml as PetReactionStatus,
PetReactionResponse, PetEmptyMetadata, PetReactionsResponse so each can
be reproduced and red/green tested against generated output.

1. anyOf of [$ref enum, inline literal enum] emitted a property typed as
   `StatusEnum?` plus `StatusEnum.fromJson(...)`, but never declared the
   enum class anywhere in lib/model/. The dart generator can't produce a
   single enum class that covers all branches and the inline-enum
   template is suppressed for composed schemas. Fix: in
   AbstractDartCodegen.fromProperty, when the composed schema has 2+
   branches and default codegen guessed at isEnum=true, drop the enum
   projection (clear isEnum, enumName, _enum, allowableValues; reset
   datatypeWithEnum=dataType). Single-element composed schemas are
   unchanged.

2. Empty-property classes emitted invalid Dart syntax: `Foo({ })` (Dart
   rejects empty named-args), a dangling `&&` on `==`, and a missing
   rhs/`;` on `hashCode`. Fix: `{{#hasVars}}` guards in
   dart_constructor.mustache and native_class.mustache. Empty classes
   now emit `Foo()`, `==> identical(this, other) || other is Foo;`,
   and `hashCode => 0;`.

3. `Map<String, Map<String, T>>` properties were decoded with
   `mapCastOfType<String, dynamic>` (returns `Map<String, dynamic>`,
   doesn't cast inner generics) which can't be assigned to the declared
   field type. Fix: native_class.mustache's nested-map branch now emits
   `(json[r'X'] as Map).map((k, v) => MapEntry(k as String, (v as Map).cast<String, T>()))`.
   Also fixes the same broken pattern in the pre-existing
   additional_properties_class.dart and map_test.dart samples.

Verified red/green: pre-fix `dart analyze` reported the exact symptoms
(undefined StatusEnum, empty-class syntax errors, Map<String, dynamic>
not assignable). Post-fix all three model files are clean; remaining
errors in the fake sample are pre-existing and unrelated. Plain
petstore_client_lib sample analyzes clean. All 88 org.openapitools
.codegen.dart.* tests pass.

Closes #23665, closes #16715
Refs #9272, #12914, #15670

Author: winrid

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

@@ -719,6 +719,19 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required) {
                             property.isModel = true;
                         });
 
+            } else if (property.isEnum) {
+                // Multi-element anyOf/oneOf where the default codegen guessed at an
+                // inline enum (e.g. anyOf of [$ref enum, inline literal enum]). The
+                // dart generator can't produce a single enum class that covers all
+                // branches, and the inline-enum template is suppressed for composed
+                // schemas, so we'd emit references to an enum class that is never
+                // declared anywhere in lib/model/. Collapse the property to its
+                // underlying primitive type instead.
+                property.isEnum = false;
+                property.datatypeWithEnum = property.dataType;
+                property.enumName = null;
+                property.allowableValues = null;
+                property._enum = null;
             }
         }
         return property;

modules/openapi-generator/src/main/resources/dart2/dart_constructor.mustache

@@ -1,10 +1,10 @@
   /// Returns a new [{{{classname}}}] instance.
-  {{{classname}}}({
+  {{{classname}}}({{#hasVars}}{
   {{#vars}}
     {{!
         A field is required in Dart when it is
         required && !defaultValue in OAS
     }}
     {{^required}}{{#vendorExtensions.x-is-optional}}this.{{{name}}}{{#defaultValue}} = const Optional.present({{#isEnum}}{{^isContainer}}const {{{enumName}}}._({{/isContainer}}{{/isEnum}}{{{.}}}{{#isEnum}}{{^isContainer}}){{/isContainer}}{{/isEnum}}){{/defaultValue}}{{^defaultValue}} = const Optional.absent(){{/defaultValue}},{{/vendorExtensions.x-is-optional}}{{/required}}{{^required}}{{^vendorExtensions.x-is-optional}}this.{{{name}}}{{#defaultValue}} = {{#isEnum}}{{^isContainer}}const {{{enumName}}}._({{/isContainer}}{{/isEnum}}{{{.}}}{{#isEnum}}{{^isContainer}}){{/isContainer}}{{/isEnum}}{{/defaultValue}},{{/vendorExtensions.x-is-optional}}{{/required}}{{#required}}{{^defaultValue}}required {{/defaultValue}}{{/required}}{{#required}}this.{{{name}}}{{#defaultValue}} = {{#isEnum}}{{^isContainer}}const {{{enumName}}}._({{/isContainer}}{{/isEnum}}{{{.}}}{{#isEnum}}{{^isContainer}}){{/isContainer}}{{/isEnum}}{{/defaultValue}},{{/required}}
   {{/vars}}
-  });
+  }{{/hasVars}});

modules/openapi-generator/src/main/resources/dart2/serialization/native/native_class.mustache

@@ -47,17 +47,17 @@ class {{{classname}}} {
 
 {{/vars}}
   @override
-  bool operator ==(Object other) => identical(this, other) || other is {{{classname}}} &&
+  bool operator ==(Object other) => identical(this, other) || other is {{{classname}}}{{#hasVars}} &&
   {{#vars}}
     {{#isMap}}_deepEquality.equals(other.{{{name}}}, {{{name}}}){{/isMap}}{{^isMap}}{{#isArray}}_deepEquality.equals(other.{{{name}}}, {{{name}}}){{/isArray}}{{^isArray}}other.{{{name}}} == {{{name}}}{{/isArray}}{{/isMap}}{{^-last}} &&{{/-last}}{{#-last}};{{/-last}}
-  {{/vars}}
+  {{/vars}}{{/hasVars}}{{^hasVars}};{{/hasVars}}
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
   {{#vars}}
     ({{#isNullable}}{{{name}}} == null ? 0 : {{/isNullable}}{{^isNullable}}{{^required}}{{^defaultValue}}{{{name}}} == null ? 0 : {{/defaultValue}}{{/required}}{{/isNullable}}{{{name}}}{{#isNullable}}!{{/isNullable}}{{^isNullable}}{{^required}}{{^defaultValue}}!{{/defaultValue}}{{/required}}{{/isNullable}}.hashCode){{^-last}} +{{/-last}}{{#-last}};{{/-last}}
-  {{/vars}}
+  {{/vars}}{{^hasVars}}    0;{{/hasVars}}
 
   @override
   String toString() => '{{{classname}}}[{{#vars}}{{{name}}}=${{{name}}}{{^-last}}, {{/-last}}{{/vars}}]';
@@ -228,7 +228,9 @@ class {{{classname}}} {
         {{{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}},
+        {{{name}}}: json[r'{{{baseName}}}'] == null
+            ? {{#defaultValue}}{{{.}}}{{/defaultValue}}{{^defaultValue}}null{{/defaultValue}}
+            : (json[r'{{{baseName}}}'] as Map).map((k, v) => MapEntry(k as String, (v as Map).cast<String, {{items.items.dataType}}>())){{#required}}{{^isNullable}}!{{/isNullable}}{{/required}},
                   {{/items.complexType}}
                 {{/items.isMap}}
                 {{^items.isMap}}

modules/openapi-generator/src/test/resources/3_0/dart/petstore-with-fake-endpoints-models-for-testing.yaml

@@ -2141,3 +2141,54 @@ components:
           $ref: '#/components/schemas/ObjectWithInlineEnum'
         object_two:
           $ref: '#/components/schemas/ObjectWithDuplicateInlineEnum'
+    PetReactionStatus:
+      type: string
+      title: PetReactionStatus
+      enum:
+        - liked
+        - disliked
+        - barked
+    PetReactionResponse:
+      type: object
+      description: |
+        Reproduces a bug where anyOf between a named-enum $ref and an inline
+        literal-enum produced a property typed as an undeclared enum class.
+        Generator must either inline a proper enum or fall back to String.
+      properties:
+        petId:
+          type: integer
+          format: int64
+        status:
+          anyOf:
+            - $ref: '#/components/schemas/PetReactionStatus'
+            - type: string
+              enum:
+                - pending-verification
+    PetEmptyMetadata:
+      description: |
+        Reproduces a bug where a schema that resolves to a class with zero
+        properties (e.g. an empty oneOf wrapper) emitted invalid Dart syntax
+        in `==`, `hashCode`, and the named-args constructor.
+      oneOf:
+        - type: string
+        - type: integer
+    PetReactionsResponse:
+      type: object
+      description: |
+        Reproduces a bug where nested `Map<String, Map<String, T>>` properties
+        were decoded with a single-level `mapCastOfType<String, dynamic>` cast
+        that can't be assigned to the declared field type.
+      properties:
+        myReacts:
+          type: object
+          additionalProperties:
+            type: object
+            additionalProperties:
+              type: boolean
+        reactionCounts:
+          type: object
+          additionalProperties:
+            type: object
+            additionalProperties:
+              type: integer
+              format: int32

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/api_response.dart

@@ -45,15 +45,17 @@ class ApiResponse {
   @override
   bool operator ==(Object other) => identical(this, other) || other is ApiResponse &&
     other.code == code &&
-    other.type == type &&
-    other.message == message;
+      other.type == type &&
+      other.message == message;
+  
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
     (code == null ? 0 : code!.hashCode) +
-    (type == null ? 0 : type!.hashCode) +
-    (message == null ? 0 : message!.hashCode);
+      (type == null ? 0 : type!.hashCode) +
+      (message == null ? 0 : message!.hashCode);
+  
 
   @override
   String toString() => 'ApiResponse[code=$code, type=$type, message=$message]';

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/category.dart

@@ -36,13 +36,15 @@ class Category {
   @override
   bool operator ==(Object other) => identical(this, other) || other is Category &&
     other.id == id &&
-    other.name == name;
+      other.name == name;
+  
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
     (id == null ? 0 : id!.hashCode) +
-    (name == null ? 0 : name!.hashCode);
+      (name == null ? 0 : name!.hashCode);
+  
 
   @override
   String toString() => 'Category[id=$id, name=$name]';

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/order.dart

@@ -61,21 +61,23 @@ class Order {
   @override
   bool operator ==(Object other) => identical(this, other) || other is Order &&
     other.id == id &&
-    other.petId == petId &&
-    other.quantity == quantity &&
-    other.shipDate == shipDate &&
-    other.status == status &&
-    other.complete == complete;
+      other.petId == petId &&
+      other.quantity == quantity &&
+      other.shipDate == shipDate &&
+      other.status == status &&
+      other.complete == complete;
+  
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
     (id == null ? 0 : id!.hashCode) +
-    (petId == null ? 0 : petId!.hashCode) +
-    (quantity == null ? 0 : quantity!.hashCode) +
-    (shipDate == null ? 0 : shipDate!.hashCode) +
-    (status == null ? 0 : status!.hashCode) +
-    (complete.hashCode);
+      (petId == null ? 0 : petId!.hashCode) +
+      (quantity == null ? 0 : quantity!.hashCode) +
+      (shipDate == null ? 0 : shipDate!.hashCode) +
+      (status == null ? 0 : status!.hashCode) +
+      (complete.hashCode);
+  
 
   @override
   String toString() => 'Order[id=$id, petId=$petId, quantity=$quantity, shipDate=$shipDate, status=$status, complete=$complete]';

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/pet.dart

@@ -49,21 +49,23 @@ class Pet {
   @override
   bool operator ==(Object other) => identical(this, other) || other is Pet &&
     other.id == id &&
-    other.category == category &&
-    other.name == name &&
-    _deepEquality.equals(other.photoUrls, photoUrls) &&
-    _deepEquality.equals(other.tags, tags) &&
-    other.status == status;
+      other.category == category &&
+      other.name == name &&
+      _deepEquality.equals(other.photoUrls, photoUrls) &&
+      _deepEquality.equals(other.tags, tags) &&
+      other.status == status;
+  
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
     (id == null ? 0 : id!.hashCode) +
-    (category == null ? 0 : category!.hashCode) +
-    (name.hashCode) +
-    (photoUrls.hashCode) +
-    (tags.hashCode) +
-    (status == null ? 0 : status!.hashCode);
+      (category == null ? 0 : category!.hashCode) +
+      (name.hashCode) +
+      (photoUrls.hashCode) +
+      (tags.hashCode) +
+      (status == null ? 0 : status!.hashCode);
+  
 
   @override
   String toString() => 'Pet[id=$id, category=$category, name=$name, photoUrls=$photoUrls, tags=$tags, status=$status]';

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/tag.dart

@@ -36,13 +36,15 @@ class Tag {
   @override
   bool operator ==(Object other) => identical(this, other) || other is Tag &&
     other.id == id &&
-    other.name == name;
+      other.name == name;
+  
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
     (id == null ? 0 : id!.hashCode) +
-    (name == null ? 0 : name!.hashCode);
+      (name == null ? 0 : name!.hashCode);
+  
 
   @override
   String toString() => 'Tag[id=$id, name=$name]';

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/model/user.dart

@@ -91,25 +91,27 @@ class User {
   @override
   bool operator ==(Object other) => identical(this, other) || other is User &&
     other.id == id &&
-    other.username == username &&
-    other.firstName == firstName &&
-    other.lastName == lastName &&
-    other.email == email &&
-    other.password == password &&
-    other.phone == phone &&
-    other.userStatus == userStatus;
+      other.username == username &&
+      other.firstName == firstName &&
+      other.lastName == lastName &&
+      other.email == email &&
+      other.password == password &&
+      other.phone == phone &&
+      other.userStatus == userStatus;
+  
 
   @override
   int get hashCode =>
     // ignore: unnecessary_parenthesis
     (id == null ? 0 : id!.hashCode) +
-    (username == null ? 0 : username!.hashCode) +
-    (firstName == null ? 0 : firstName!.hashCode) +
-    (lastName == null ? 0 : lastName!.hashCode) +
-    (email == null ? 0 : email!.hashCode) +
-    (password == null ? 0 : password!.hashCode) +
-    (phone == null ? 0 : phone!.hashCode) +
-    (userStatus == null ? 0 : userStatus!.hashCode);
+      (username == null ? 0 : username!.hashCode) +
+      (firstName == null ? 0 : firstName!.hashCode) +
+      (lastName == null ? 0 : lastName!.hashCode) +
+      (email == null ? 0 : email!.hashCode) +
+      (password == null ? 0 : password!.hashCode) +
+      (phone == null ? 0 : phone!.hashCode) +
+      (userStatus == null ? 0 : userStatus!.hashCode);
+  
 
   @override
   String toString() => 'User[id=$id, username=$username, firstName=$firstName, lastName=$lastName, email=$email, password=$password, phone=$phone, userStatus=$userStatus]';