MvvmAIO.R3.SourceGenerators 0.6.1

MvvmAIO.R3.SourceGenerators

Roslyn source generators for R3-based MVVM workflows.

Stability

This project is in an early stage. Until 1.0.0 is published, breaking changes may occur without a long deprecation window (API surface, generated code shape, namespaces, and package layout can all change). When upgrading, review CHANGELOG.md or GitHub releases.

Features

• Observable events — FromEvents(), FromEventHandlers(), and routed FromRoutedEvents() / FromRoutedEventHandlers() (WPF when UseWPF is true; Avalonia when RoutedEvent<T> metadata is present). Entry extensions live in R3.SourceGenerators; streams use R3.Observable from R3. Per-event surfaces are properties on generated internal interfaces (ReactiveMarbles-style chaining).
• Interface-based codegen — event interfaces (e.g. IButtonEvents, IButtonRoutedEvents) and sealed implementations mirror the source type hierarchy. See docs/design-interface-based-event-generation.md.
• Generic constraints — source.FromEvents() inside where T : Base, I1, I2 resolves to a combined interface inheriting all constraint event interfaces.
• [R3Command] (MvvmAIO.R3) — generates ReactiveCommand properties on partial types, with optional CanExecute and CommandName.
• Multi-Roslyn — analyzer builds for Roslyn 4.3 / 4.12 / 5.x; MSBuild selects the matching folder under analyzers/dotnet/.
• NRT — generated code preserves nullable annotations from original event signatures.

Installation

dotnet add package MvvmAIO.R3.SourceGenerators

The package is a DevelopmentDependency analyzer. Add using R3.SourceGenerators; for extension methods. Generated interfaces and implementations are internal in that namespace.

Quick start

FromEvents / FromEventHandlers

public class Button : Control
{
    public event EventHandler<RoutedEventArgs>? Click;
}

// Returns IButtonEvents (internal interface).
var clicks = button.FromEvents().Click;

Hierarchy — one entry point, events from bases and interfaces:

public class BaseSource { public event Action? BaseChanged; }
public interface INotify { event EventHandler? Notified; }
public class DerivedSource : BaseSource, INotify
{
    public event Action<int>? DerivedChanged;
    public event EventHandler? Notified { add; remove; }
}

DerivedSource d = new();
_ = d.FromEvents().BaseChanged;
_ = d.FromEvents().Notified;
_ = d.FromEvents().DerivedChanged;

Generic constraints:

static void Run<T>(T source) where T : BaseSource, IFirst, ISecond
{
    _ = source.FromEvents().BaseChanged;
    _ = source.FromEvents().FirstChanged;
    _ = source.FromEvents().SecondChanged;
}

Routed events (WPF / Avalonia)

Same interface + property model as FromEvents (e.g. IButtonRoutedEvents). Parameterless calls use default Avalonia routes (Direct | Bubble, handledEventsToo: false).

var clicks = button.FromRoutedEvents().Click;
var clickHandlers = button.FromRoutedEventHandlers().Click;

Explicit routing (Avalonia):

var pointerPressed = control
    .FromRoutedEvents(
        Avalonia.Interactivity.RoutingStrategies.Tunnel | Avalonia.Interactivity.RoutingStrategies.Bubble,
        handledEventsToo: true)
    .PointerPressed;

Attached routed events (still Observable<T> extensions, not the interface model):

var childClicks = panel.FromAttachedRoutedEvent(
    Avalonia.Controls.Button.ClickEvent,
    Avalonia.Interactivity.RoutingStrategies.Bubble,
    handledEventsToo: true);

Interface-only event sources

public interface INotifyMore : INotifySomething
{
    event Action? MoreChanged;
}

static void Run(INotifyMore s)
{
    _ = s.FromEvents().SomethingChanged;
    _ = s.FromEvents().MoreChanged;
}

[R3Command]

Apply to instance methods on a partial class or struct. The generator adds a public {Name}Command property (or CommandName) backed by ReactiveCommand.

Minimal example:

public partial class ShellViewModel
{
    private readonly Observable<bool> _canSave = new(true);

    [R3Command(CanExecute = nameof(_canSave))]
    private async Task Save() { /* ... */ }
}

Method signature matrix

Attribute members

Diagnostics

Event-related warnings (R3SG2001, R3SG2002) apply to unsupported event delegate shapes for FromEvents / FromEventHandlers.

Design documentation

• Interface-based event generation — naming, hierarchy, routed events, file layout.
• CHANGELOG.md — release notes and upgrade compatibility (including SyntaxFactory internal migration).

Samples

Runnable demos: MvvmAIO.R3.SourceGenerators.Samples (WPF + Avalonia).