ConsoleForge.SourceGen

Roslyn source generator for ConsoleForge. Eliminates Update(IMsg) dispatch boilerplate from your models and components.

Installation

dotnet add package ConsoleForge
dotnet add package ConsoleForge.SourceGen

Note: This is a development dependency — it runs at compile time and produces no runtime overhead.

[DispatchUpdate] — Auto-generated Update dispatch

Instead of writing the Update switch by hand:

public (IModel Model, ICmd? Cmd) Update(IMsg msg) => msg switch
{
    NavUpMsg   => OnNavUp(),
    NavDownMsg => OnNavDown(),
    SelectMsg  => OnSelect(),
    _          => (this, null),
};

Mark the type partial and add [DispatchUpdate]:

[DispatchUpdate]
sealed partial record ListPage(int Index = 0) : IComponent
{
    static readonly KeyMap Keys = new KeyMap()
        .On(ConsoleKey.UpArrow,   () => new NavUpMsg())
        .On(ConsoleKey.DownArrow, () => new NavDownMsg())
        .On(ConsoleKey.Enter,     () => new SelectMsg());
 
    public ICmd? Init() => null;
    public IWidget View() => new ConsoleForge.Widgets.List(Items, Index);
 
    // Generator finds On{X} methods → emits Update() with a switch
    (IModel, ICmd?) OnNavUp()   => (this with { Index = Index - 1 }, null);
    (IModel, ICmd?) OnNavDown() => (this with { Index = Index + 1 }, null);
    (IModel, ICmd?) OnSelect()  => (this with { Result = Items[Index] }, null);
}

The generator:

1. Finds all methods matching (IModel, ICmd?) On{X}(...)
2. Looks for a corresponding {X}Msg type in scope
3. Emits the Update(IMsg) switch with one arm per handler
4. Detects a static KeyMap Keys field → emits Keys.Handle(msg) pre-dispatch
5. Default arm returns (this, null)

Handler conventions

Pattern	Generated switch arm
(IModel, ICmd?) OnFoo()	FooMsg => OnFoo(),
(IModel, ICmd?) OnFoo(FooMsg msg)	FooMsg __m => OnFoo((FooMsg)__m),

[Component] — Scaffold boilerplate

When combined with [DispatchUpdate] (or used alone), [Component] generates:

• IComponent<T>.Result explicit interface implementation (reads from your Result property)
• public ICmd? Init() => null; (when not already declared)

[DispatchUpdate, Component]
sealed partial record FilePicker(string? Result = null) : IComponent<string>
{
    public IWidget View() => ...;
 
    (IModel, ICmd?) OnPick(PickMsg msg) => (this with { Result = msg.Path }, null);
    (IModel, ICmd?) OnCancel()          => (this, null);
}
 
// Generated:
// - string IComponent<string>.Result => Result!;
// - public ICmd? Init() => null;
// - public (IModel, ICmd?) Update(IMsg msg) => msg switch { ... };

Diagnostics

Code	Severity	Description
CFG001	Error	Type must be declared partial to use [DispatchUpdate]
CFG002	Warning	Handler skipped — message type not found or duplicate handler
CFG003	Warning	Handler return type must be (IModel, ICmd?)
CFG004	Info	Type already declares Update(IMsg) — generator skips dispatch

Requirements

• ConsoleForge ≥ 0.2.0 (provides the trigger attributes)
• .NET SDK ≥ 8.0
• No runtime dependency — the generator runs at compile time only

License

MIT — see LICENSE.