feat(reactive): add ContainerDisposable for CompositeDisposable interop (#169)

- Add ContainerDisposable, a MultipleDisposable that converts implicitly to a
  CompositeDisposable it owns and disposes, so a disposal group flows into APIs
  written against System.Reactive without a hand conversion.
- MultipleDisposable ships in the dependency-free ReactiveUI.Disposables package
  and cannot name CompositeDisposable, so the seam has to live here.
- Add a DisposeWith overload taking the container. Without it a call site that
  imports this namespace and System.Reactive's fluent disposal helpers has two
  equally-good candidates and is ambiguous.

Author: glennawatson

README.md

@@ -83,6 +83,12 @@ These two types are the only places the lean surface departs from the System.Rea
 variants close the gap: they recompile the same source with `ISequencer` mapped to `IScheduler` and `RxVoid` mapped to
 `System.Reactive.Unit`, so code that already speaks System.Reactive sees the types it expects.
 
+Disposal groups are a third seam, and one the shared types cannot close on their own: `MultipleDisposable` ships in the
+dependency-free `ReactiveUI.Disposables` package, so it cannot name `CompositeDisposable`. `ReactiveUI.Primitives.Reactive`
+adds `ContainerDisposable` for that - a `MultipleDisposable` that converts implicitly to a `CompositeDisposable` it owns
+and disposes. Hand one to `DisposeWith`, to a library that takes a `CompositeDisposable`, or to your own helper, and it
+just works; anything registered through the composite is disposed with the container.
+
 ## Table of contents
 
 1. [Install](#install)

src/ReactiveUI.Primitives.Reactive/Disposables/ContainerDisposable.cs

@@ -0,0 +1,112 @@
+// Copyright (c) 2019-2026 ReactiveUI Association Incorporated. All rights reserved.
+// ReactiveUI Association Incorporated licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System.Reactive.Disposables;
+
+namespace ReactiveUI.Primitives.Reactive.Disposables;
+
+/// 
+/// A  that a System.Reactive consumer can use as a
+/// , so an activation-scoped container flows into APIs written against
+/// System.Reactive - DisposeWith above all - without the caller converting it by hand.
+/// 
+/// 
+/// 
+/// The conversion is identity-stable: every conversion of the same container yields the same
+/// , and the container owns that composite, so anything registered through it
+/// is disposed when the container is. Registering after the container is disposed disposes the registration
+/// immediately, matching .
+/// 
+/// 
+/// Registrations made through the composite are not visible to the container's own
+///  members: the composite occupies a single slot, so Count counts it once
+/// and Contains/Remove do not see through it.
+/// 
+/// 
+[System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+public sealed class ContainerDisposable : MultipleDisposable
+{
+    /// Serializes creation of the composite.
+    private readonly Lock _gate = new();
+
+    /// The composite handed to System.Reactive consumers, created on first conversion.
+    private CompositeDisposable? _composite;
+
+    /// Initializes a new instance of the  class.
+    public ContainerDisposable()
+    {
+    }
+
+    /// Initializes a new instance of the  class.
+    /// The first disposable.
+    /// The second disposable.
+    public ContainerDisposable(IDisposable first, IDisposable second)
+        : base(first, second)
+    {
+    }
+
+    /// Initializes a new instance of the  class.
+    /// The first disposable.
+    /// The second disposable.
+    /// The third disposable.
+    public ContainerDisposable(IDisposable first, IDisposable second, IDisposable third)
+        : base(first, second, third)
+    {
+    }
+
+    /// Initializes a new instance of the  class from a group of disposables.
+    /// Disposables that will be disposed together.
+    ///  is .
+    public ContainerDisposable(params IDisposable[] disposables)
+        : base(disposables)
+    {
+    }
+
+    /// Hands the container to a System.Reactive consumer as the composite it owns.
+    /// The container to convert.
+    ///  is .
+    public static implicit operator CompositeDisposable(ContainerDisposable container)
+    {
+        ArgumentExceptionHelper.ThrowIfNull(container);
+
+        return container.ToCompositeDisposable();
+    }
+
+    /// Gets the  this container owns, creating it on first call.
+    /// The composite whose contents are disposed along with this container.
+    public CompositeDisposable ToCompositeDisposable()
+    {
+        lock (_gate)
+        {
+            // A disposed composite is still the right answer once the container itself is disposed - it is the
+            // sink that disposes late arrivals. After Clear() or Remove() the container lives on, so a composite
+            // it disposed has to be replaced rather than handed out again.
+            var existing = _composite;
+            if (existing is not null && (!existing.IsDisposed || IsDisposed))
+            {
+                return existing;
+            }
+
+            var created = new CompositeDisposable();
+            _composite = created;
+
+            // Registering the composite with the container is what ties the two lifetimes together. On an
+            // already-disposed container this disposes the composite instead, which is what a caller adding to
+            // a disposed container should get.
+            Add(created);
+            return created;
+        }
+    }
+
+    /// 
+    protected override void Dispose(bool disposing)
+    {
+        base.Dispose(disposing);
+
+        // The composite occupies a slot in the container, so the base disposed it just now - or Clear()/Remove()
+        // did on the way out. Disposing it here is idempotent and states the ownership outright. Nothing in this
+        // hierarchy has a finalizer and the class is sealed, so this only ever runs on the deterministic path.
+        _composite?.Dispose();
+    }
+}

src/ReactiveUI.Primitives.Reactive/Disposables/LinqExtensions.ContainerDisposable.cs

@@ -0,0 +1,37 @@
+// Copyright (c) 2019-2026 ReactiveUI Association Incorporated. All rights reserved.
+// ReactiveUI Association Incorporated licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using ReactiveUI.Primitives.Reactive.Disposables;
+
+namespace ReactiveUI.Primitives.Reactive;
+
+/// Miscellaneous Primitives extensions.
+public static partial class LinqExtensions
+{
+    /// Disposal-tracking operators for a disposable.
+    /// The disposable type.
+    /// The disposable.
+    extension<T>(T disposable)
+        where T : IDisposable
+    {
+        /// Disposes the IDisposable with the container.
+        /// The container.
+        /// The original disposable.
+        ///  is .
+        /// 
+        /// A  converts to a System.Reactive CompositeDisposable, so
+        /// without this overload a call site that imports both this namespace and System.Reactive's fluent
+        /// disposal helpers has two equally-good candidates - the inherited
+        /// DisposeWith(MultipleDisposable) and System.Reactive's DisposeWith(CompositeDisposable)
+        /// - and is ambiguous. Taking the container exactly makes this an identity match, which wins outright.
+        /// 
+        public T DisposeWith(ContainerDisposable disposables)
+        {
+            ArgumentExceptionHelper.ThrowIfNull(disposables);
+
+            disposables.Add(disposable);
+            return disposable;
+        }
+    }
+}

src/ReactiveUI.Primitives.Reactive/PublicAPI/net10.0-android/PublicAPI.txt

@@ -425,6 +425,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1598,6 +1599,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]

src/ReactiveUI.Primitives.Reactive/PublicAPI/net10.0-ios/PublicAPI.txt

@@ -425,6 +425,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1592,6 +1593,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]

src/ReactiveUI.Primitives.Reactive/PublicAPI/net10.0-maccatalyst/PublicAPI.txt

@@ -425,6 +425,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1592,6 +1593,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]

src/ReactiveUI.Primitives.Reactive/PublicAPI/net10.0-macos/PublicAPI.txt

@@ -425,6 +425,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1592,6 +1593,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]

src/ReactiveUI.Primitives.Reactive/PublicAPI/net10.0-tvos/PublicAPI.txt

@@ -425,6 +425,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1592,6 +1593,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]

src/ReactiveUI.Primitives.Reactive/PublicAPI/net10.0/PublicAPI.txt

@@ -424,6 +424,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1572,6 +1573,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]

src/ReactiveUI.Primitives.Reactive/PublicAPI/net11.0-android/PublicAPI.txt

@@ -425,6 +425,7 @@ namespace ReactiveUI.Primitives.Reactive
         extension(T disposable) where T : System.IDisposable
         {
             public T DisposeWith(ReactiveUI.Primitives.Disposables.MultipleDisposable disposables) { }
+            public T DisposeWith(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable disposables) { }
         }
         extension(System.IObservable source)
         {
@@ -1598,6 +1599,20 @@ namespace ReactiveUI.Primitives.Reactive.Core
         public override readonly string ToString() { }
     }
 }
+namespace ReactiveUI.Primitives.Reactive.Disposables
+{
+    [System.Diagnostics.DebuggerDisplay("Count = {Count}, IsDisposed = {IsDisposed}")]
+    public sealed class ContainerDisposable : ReactiveUI.Primitives.Disposables.MultipleDisposable
+    {
+        public ContainerDisposable() { }
+        public ContainerDisposable(params System.IDisposable[] disposables) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second) { }
+        public ContainerDisposable(System.IDisposable first, System.IDisposable second, System.IDisposable third) { }
+        protected override void Dispose(bool disposing) { }
+        public System.Reactive.Disposables.CompositeDisposable ToCompositeDisposable() { }
+        public static implicit operator System.Reactive.Disposables.CompositeDisposable(ReactiveUI.Primitives.Reactive.Disposables.ContainerDisposable container) { }
+    }
+}
 namespace ReactiveUI.Primitives.Reactive.Signals
 {
     [System.Diagnostics.DebuggerDisplay("Count = {_count}, MaximumCount = {_maximumCount}, IsDraining = {_isDraining}")]