Lombok.NET 2.3.1

Lombok.NET

This library is to .NET what Lombok is to Java. It generates constructors and other fun stuff using Source Generators for those classes you specify special attributes for. Check out the examples for more info.

Installation

At least Visual Studio 17.3 (or any JetBrains Rider version) is required for projects using this library. The generators generate code compliant with C# 10. You can install Lombok.NET either via NuGet

Install-Package Lombok.NET

Or via the .NET Core command-line interface:

dotnet add package Lombok.NET

Building and Debugging

When building from source in the "Debug" configuration, the build will be suspended until a debugger is attached to the build process.
During this time it is possible to set break points inside the generators or analyzers, before attaching to the build process in order for it to continue.
This behavior does not exist for the "Release" configuration, so if you just want to run tests or see if a build succeeds, this is best done in the "Release" configuration.

Features

• Constructors
• "With" methods
• Singletons
• Lazy
• INotifyPropertyChanged/INotifyPropertyChanging
• Async overloads
• ToString
• Freezable pattern
• Decorator pattern

Usage

Demo

This demonstrates the generating of the With pattern. Simply apply an attribute and the library will do the rest. Remember you are not bound to using fields, but can also use properties and supply the appropriate MemberType value to the attribute's constructor.

Constructors

Supported types: Classes, Structs (AllArgsConstructor only)

[AllArgsConstructor]
public partial class Person {
    private string _name;
    private int _age;
}

By supplying the AllArgsConstructor attribute and making the type partial, you allow the Source Generator to create a constructor for it containing all of the classes private fields.
If you wish to modify this behavior and would instead like to have a constructor generated off of public properties, you can specify this in the attribute's constructor, e.g.:

[AllArgsConstructor(MemberType = MemberType.Property, AccessTypes = AccessTypes.Public)]
public partial class Person {
    public string Name { get; set; }
    public int Age { get; set; }
}

The default is Field for the MemberType and Private for the AccessType.
It is crucial to make the type partial, otherwise the Source Generator will not be able to generate a constructor and will throw an exception.

If you only wish to have a constructor generated containing the required fields or properties, Lombok.NET offers the RequiredArgsConstructor attribute. Fields are required if they are readonly, properties are required if they don't have a set accessor.
There is also a NoArgsConstructor attribute which generates an empty constructor.

With Methods

Supported types: Classes

For modifying objects after they were created, a common pattern using With... methods is used. Lombok.NET will generate these methods for you based on members in your class. Here's an example:

[AllArgsConstructor]
[With]
public partial class Person {
    private string _name;
    private int _age;
}

class Program {
    public static void Main() {
        var person = new Person("Steve", 22);
        person = person.WithName("Collin");
        
        Console.WriteLine(person.Name); // Prints "Collin"
    }
}

With methods will only be generated for properties with a setter and fields without the readonly modifier.

Singletons

Supported types: Classes

Apply the Singleton attribute to a partial class and Lombok.NET will generate all the boilerplate code required for making your class a thread-safe, lazy singleton. It will create a property called Instance in order to access the singleton's instance. Note that the type needs to have a parameterless constructor.
Example:

[Singleton]
public partial class PersonRepository {
}

public class MyClass {
    public MyClass() {
        var personRepository = PersonRepository.Instance;
    }
}

Lazy

Supported types: Classes, Structs

Apply the Lazy attribute to a partial class or struct and Lombok.NET will generate a Lazy<T> property which can be used to create an instance of the object lazily. Note that the type needs to have a parameterless constructor. Example:

[Lazy]
public partial class HeavyInitialization {
    private HeavyInitialization() {
        Thread.Sleep(1000);
    }
}

public class Program {
    public Program() {
        var lazy = HeavyInitialization.Lazy;
        if(Random.Shared.Next() == 2) {
            var value = lazy.Value;
            // do something with value
        }
    }
}

ToString

Supported types: Classes, Structs, Enums

To generate a descriptive ToString method to your type, make it partial and add the [ToString] attribute to it. By default, it will include private fields in the ToString method, but this is customizable in the attribute's constructor.

[ToString]
public partial class Person {
    private string _name;
    private int _age;
}

When applying this attribute to an enum, Lombok.NET will create an extension class with a ToText method. This is due to the fact that enums can't be partial, thus an extension method is needed and the extension method will not be found if it is called ToString.

If you have sensitive data in your objects which should not be contained in the ToString method, you can apply the [Masked] attribute to the property or field containing sensitive data. This will cause the value to be replaced by four asterisks (****) in the ToString method.

Properties

Supported types: Classes, Structs

Generating properties from fields while using them as backing fields is possible using the [Property] attribute. Example:

public partial class MyViewModel {
    
    [Property]
    private int _result;
}

This will create the following property:

public int Result {
    get => _result;
    set => _result = value;
}

Property change pattern

Supported types: Classes

All of the boilerplate code surrounding ÌNotifyPropertyChanged/ÌNotifyPropertyChanging can be generated using a conjunction of the [NotifyPropertyChanged]/[NotifyPropertyChanging] and the [Property] attributes.
The [NotifyPropertyChanged] attribute will implement the INotifyPropertyChanged interface and the PropertyChanged event. It will also create a method called SetFieldAndRaisePropertyChanged which sets a backing field and raises the event. The event as well as the method can be used in your ViewModels to implement desired behavior.
If you would like to take it a step further, you can also use the [Property] attribute on backing fields while passing the PropertyChangeType parameter to generate properties off of backing fields which will include the raising of the specific event in their setters. Here's an example:

[NotifyPropertyChanged]
public partial class CustomViewModel {

    private int _result;
    
    public int Result {
        get => _result;
        set => SetFieldAndRaisePropertyChanged(out _result, value);
    }
    
    // -- OR --
    
    [Property(PropertyChangeType = PropertyChangeType.PropertyChanged)]
    private int _result;
}

public class Program {

    public static void Main() {
        var vm = new CustomViewModel();
        vm.PropertyChanged += (sender, args) => Console.WriteLine("A property was changed");
        
        vm.Result = 42;
    }
}

If you are using the ReactiveUI library (e.g. when using Avalonia), you can also specify the PropertyChangeType.ReactivePropertyChange to leverage ReactiveUI's property change handling.

To be able to generate the properties with the property change-raising behavior, the class must have the [NotifyPropertyChanged] or [NotifyPropertyChanging] (depending on desired behavior) attribute placed above it.

Async overloads

Supported types: Abstract Classes, Interfaces, Methods

If you want to have async overloads for every method in your interface, you can add the [AsyncOverloads] attribute to it. This also works for abstract classes:

[AsyncOverloads]
public partial interface IRepository<T> {
    T GetById(int id);
    
    void Save(T entity);
}

This will add the following methods to your interface:

Task<T> GetByIdAsync(int id);
Task SaveAsync(T entity);

For abstract classes, it will do the same for every abstract method. The inheriting class will be forced to implement the async versions as well. This may also be achieved by using the [Async] attribute.

Async methods

If you would like to create a simple async version of your method, you can add the [Async] attribute to it:

public partial class MyViewModel {

    [Async]
    public int Square(int i) {
        return i * i;
    }
}

This will add the following method:

public Task<int> SquareAsync(int i) => Task.FromResult(Square(i));

This works for classes and structs, however it must be partial.

Freezable pattern

Supported types: Classes and structs

The [Freezable] attribute can be used to generate the freezable pattern for types. For example:

[Freezable]
partial class Person
{
	[Freezable]
	private string _name;

	private int _age;
}

This would generate the methods Freeze(), Unfreeze(), TryFreeze(), and TryUnfreeze() and a property to check the freeze status, IsFrozen, as well as the property Name for the _name field. When trying to set the Name property, the setter will check if the type is currently frozen and throw an InvalidOperationException if this is the case.
The attribute must be set on both the fields which should be aware of the type's freeze status as well as the type itself. Readonly fields will be ignored.
If an instance should not be able to be unfrozen, it is possible to specify [Freezable(IsUnfreezable = false)] on the type.

Decorator Pattern

Supported types: Abstract Classes, Interfaces

Lombok.NET also provides an option to generate the boilerplate code when it comes to the decorator pattern. Simply apply the Decorator attribute to an abstract class or an interface and let the Source Generator do the rest.

[Decorator]
public interface IVehicle {
    void Drive();
    int GetNumberOfWheels();
} 

This will add the following class to your namespace:

public class VehicleDecorator {

    private readonly IVehicle _vehicle;
    
    public VehicleDecorator(IVehicle vehicle) {
        _vehicle = vehicle;
    }
    
    public virtual void Drive() {
        _vehicle.Drive();
    }
    
    public virtual int GetNumberOfWheels() {
        return _vehicle.GetNumberOfWheels();
    }
} 

Please let me know if there is any other functionality you would like to see in this library. I am happy to add more features.