Freezed 3.2.3: Generated mixin getters compressed to single line causing compilation errors

[bobhu2k]

Bug Description

Freezed 3.2.3 generates mixin code with all getters compressed on a single line, causing the Dart analyzer to fail recognizing these as implementations, resulting in missing abstract member errors.

Steps to Reproduce

1. Create a simple Freezed model:

import 'package:freezed_annotation/freezed_annotation.dart';

part 'test_model.freezed.dart';
part 'test_model.g.dart';

@freezed
class TestModel with _$TestModel {
  const TestModel._();

  const factory TestModel({
    required String userId,
    required String deviceId,
    required String displayName,
  }) = _TestModel;

  factory TestModel.fromJson(Map<String, dynamic> json) => _$TestModelFromJson(json);
}

2. Run code generation:

flutter pub run build_runner build --delete-conflicting-outputs

3. Run analyzer:

flutter analyze

Expected Result

Generated mixin should have each getter on a separate line:

mixin _$TestModel {
  String get userId => throw _privateConstructorUsedError;
  String get deviceId => throw _privateConstructorUsedError;
  String get displayName => throw _privateConstructorUsedError;
  // ...
}

Actual Result

Freezed 3.2.3 compresses all getters on one line:

mixin _$TestModel {
 String get userId; String get deviceId; String get displayName;
  // ...
}

This causes compilation errors:

error • Missing concrete implementations of 'getter mixin _$TestModel on Object.deviceId',
'getter mixin _$TestModel on Object.displayName',
'getter mixin _$TestModel on Object.userId',
and 'mixin _$TestModel on Object.toJson'
• lib/test_model.dart:7:7 • non_abstract_class_inherits_abstract_member

Environment

• Freezed: 3.2.3
• freezed_annotation: 3.1.0
• build_runner: 2.10.2 (also reproduced on 2.7.1)
• Flutter SDK: 3.27.0
• Dart SDK: 3.8.0+
• OS: macOS Darwin 23.2.0

Dependency Versions

dependencies:
  freezed_annotation: 3.1.0

dev_dependencies:
  freezed: 3.2.3
  build_runner: 2.7.1 or 2.10.2
  json_serializable: 6.11.1

Workaround

Downgrading to Freezed 2.5.2 resolves the issue:

dependencies:
  freezed_annotation: 2.4.4
  json_annotation: 4.9.0

dev_dependencies:
  freezed: 2.5.2
  build_runner: 2.4.13
  json_serializable: 6.8.0

Note: Downgrading Freezed to 2.5.2 requires downgrading related dependencies due to source_gen version conflicts.

Verification

This issue reproduces in a clean Flutter project, confirming it's a Freezed 3.2.3 code generation bug, not a usage error.

Impact

This bug affects all @freezed classes with multiple fields using Freezed 3.2.3.

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Is this issue already known? Is there a fix plan? We're happy to provide more information or test fixes.

[bobhu2k]

Sorry, created in wrong repository. This should be tracked internally in our project.