fix: schema aliases can now be dereferenced correctly

lib/src/open_api/index.dart

@@ -59,6 +59,7 @@ bool _checkReferenceTypes(name, ref, self) {
       return true;
     } else if (self is SchemaObject) {
       // Reference types can be different if the reference is a SchemaObject
+      // should this return true?
       return false;
     } else {
       throw Exception(

lib/src/open_api/schema.dart

@@ -257,6 +257,7 @@ class Schema with _$Schema {
       );
     }
 
+    // schema alias issue is caused by _checkReferenceTypes returning false
     final isMatch = _checkReferenceTypes(ref, sRef, this);
 
     if (!isMatch) {

test/generation/alias.json

@@ -0,0 +1,25 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "schema",
+    "description": "Schema",
+    "version": "1.0.0"
+  },
+  "paths": {
+  },
+  "components": {
+    "schemas": {
+      "MyAlias": {
+        "type": "string"
+      },
+      "MyObject": {
+        "type": "object",
+        "properties": {
+          "myField": {
+            "$ref": "#/components/schemas/MyAlias"
+          }
+        }
+      }
+    }
+  }
+}

test/generation/ref_alias_test.dart

@@ -0,0 +1,103 @@
+import 'dart:io';
+
+import 'package:openapi_spec/openapi_spec.dart';
+import 'package:path/path.dart' as p;
+import 'package:test/test.dart';
+
+void main() {
+  final tmp = Directory(
+    p.join('test', 'tmp', 'generation'),
+  );
+
+  final truthJson = p.join('test', 'generation', 'alias.json');
+
+  late OpenApi spec;
+
+  void createTmpDir() {
+    if (tmp.existsSync()) {
+      tmp.deleteSync(recursive: true);
+    }
+    tmp.createSync(recursive: true);
+  }
+
+  group('Alias', () {
+    setUp(() {
+      spec = OpenApi.fromFile(source: truthJson);
+      createTmpDir();
+    });
+
+    /// Test schema generation (single file)
+    test('Can dereference ref alias', () async {
+      final model = spec.components!.schemas!["MyObject"]! as SchemaObject;
+      final field = model.properties!["myField"];
+      expect(field!.ref, equals("MyAlias"));
+
+      final dereferenced = field.dereference(components: spec.components!.schemas);
+
+      // the deferenced schema should now be a string
+      expect(dereferenced.type, equals(SchemaType.string));
+      expect(dereferenced.ref, isNull);
+    });
+
+    test('Generate Schema Code', () async {
+      final dir = tmp.createTempSync();
+      await spec.generate(
+        package: 'alias',
+        quiet: true,
+        replace: true,
+        destination: dir.path,
+        schemaOptions: SchemaGeneratorOptions(
+          singleFile: true,
+        ),
+      );
+      final genDir = Directory(p.join(dir.path, 'schema'));
+      final genFiles = genDir.listSync();
+      expect(genFiles.length, 1);
+      expect(File(p.joinAll([genDir.path, "schema.dart"])).readAsStringSync(), equals(r'''
+// coverage:ignore-file
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// ignore_for_file: type=lint
+// ignore_for_file: invalid_annotation_target
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'schema.g.dart';
+part 'schema.freezed.dart';
+
+// ==========================================
+// CLASS: MyObject
+// ==========================================
+
+/// No Description
+@freezed
+class MyObject with _$MyObject {
+  const MyObject._();
+
+  /// Factory constructor for MyObject
+  const factory MyObject({
+    /// No Description
+    @JsonKey(includeIfNull: false) String? myField,
+  }) = _MyObject;
+
+  /// Object construction from a JSON representation
+  factory MyObject.fromJson(Map<String, dynamic> json) =>
+      _$MyObjectFromJson(json);
+
+  /// List of all property names of schema
+  static const List<String> propertyNames = ['myField'];
+
+  /// Perform validations on the schema property values
+  String? validateSchema() {
+    return null;
+  }
+
+  /// Map representation of object (not serialized)
+  Map<String, dynamic> toMap() {
+    return {
+      'myField': myField,
+    };
+  }
+}
+'''));
+    });
+  });
+}