Add OAPH From Partial Property (#174)

* Add OAPH From Partial Property

* Update Readme, update version for release

Author: ChrisPulman

README.md

@@ -12,8 +12,10 @@ This documentation covers using ReactiveUI Source Generators to simplify and enh
 ReactiveUI Source Generators automatically generate ReactiveUI objects to streamline your code. These Source Generators are designed to work with ReactiveUI V19.5.31+ and support the following features:
 
 - `[Reactive]` With field and access modifiers, partial property support (C# 13 Visual Studio Version 17.12.0)
-- `[ObservableAsProperty]`
+- `[ObservableAsProperty]` With field, method, Observable property and partial property support (C# 13 Visual Studio Version 17.12.0)
+- `[ObservableAsProperty(ReadOnly = false)]` Removes readonly keyword from the generated helper field
 - `[ObservableAsProperty(PropertyName = "ReadOnlyPropertyName")]`
+- `[ObservableAsProperty(InitialValue = "Default Value")]` Only valid for partial properties using (C# 13 Visual Studio Version 17.12.0)
 - `[ReactiveCommand]`
 - `[ReactiveCommand(CanExecute = nameof(IObservableBoolName))]` with CanExecute
 - `[ReactiveCommand(OutputScheduler = "RxApp.MainThreadScheduler")]` using a ReactiveUI Scheduler
@@ -296,6 +298,26 @@ public partial class MyReactiveClass : ReactiveObject
 }
 ```
 
+### Usage ObservableAsPropertyHelper with partial Property and a default value
+```csharp
+using ReactiveUI.SourceGenerators;
+
+public partial class MyReactiveClass : ReactiveObject
+{
+    public MyReactiveClass()
+    {
+        // The value of MyProperty will be "Default Value" until the Observable is initialized
+        _myPrpertyHelper = MyPropertyObservable()
+            .ToProperty(this, nameof(MyProperty));
+    }
+    
+    [ObservableAsProperty(InitialValue = "Default Value")]
+    public string MyProperty { get; }
+
+    public IObservable<string> MyPropertyObservable() => Observable.Return("Test Value");
+}
+```
+
 ## Usage ReactiveCommand `[ReactiveCommand]`
 
 ### Usage ReactiveCommand without parameter

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromField#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -0,0 +1,54 @@
+//HintName: ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.cs
+// Copyright (c) 2025 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System;
+
+// <auto-generated/>
+#pragma warning disable
+#nullable enable
+namespace ReactiveUI.SourceGenerators;
+
+/// <summary>
+/// ObservableAsPropertyAttribute.
+/// </summary>
+/// <seealso cref="Attribute" />
+[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property | AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+internal sealed class ObservableAsPropertyAttribute : Attribute
+{
+    /// <summary>
+    /// Gets the name of the property.
+    /// </summary>
+    /// <value>
+    /// The name of the property.
+    /// </value>
+    public string? PropertyName { get; init; }
+
+    /// <summary>
+    /// Gets the Readonly state of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The is read only of the OAPH property.
+    /// </value>
+    public bool ReadOnly { get; init; } = true;
+
+    /// <summary>
+    /// Gets the AccessModifier of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The AccessModifier of the OAPH property, protected if true.
+    /// </value>
+    public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
+}
+#nullable restore
+#pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromField#TestNs.TestVM.ObservableAsProperties.g.verified.cs

@@ -0,0 +1,23 @@
+//HintName: TestNs.TestVM.ObservableAsProperties.g.cs
+// <auto-generated/>
+#pragma warning disable
+#nullable enable
+namespace TestNs
+{
+    /// <summary>
+    /// Partial class for the TestVM which contains ReactiveUI Observable As Property initialization.
+    /// </summary>
+    public partial class TestVM
+    {
+        /// <inheritdoc cref="_testPropertyHelper"/>
+        private readonly ReactiveUI.ObservableAsPropertyHelper<double?> _testPropertyHelper;
+
+        /// <inheritdoc cref="_testProperty"/>
+        [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+        [global::System.Runtime.Serialization.DataMemberAttribute()]
+        [global::System.Text.Json.Serialization.JsonIncludeAttribute()]
+        public double? TestProperty { get => _testProperty = (_testPropertyHelper == null ? _testProperty : _testPropertyHelper.Value); }
+    }
+}
+#nullable restore
+#pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservableMethods#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -41,6 +41,14 @@ internal sealed class ObservableAsPropertyAttribute : Attribute
     /// The AccessModifier of the OAPH property, protected if true.
     /// </value>
     public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
 }
 #nullable restore
 #pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservableMethodsWithName#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -41,6 +41,14 @@ internal sealed class ObservableAsPropertyAttribute : Attribute
     /// The AccessModifier of the OAPH property, protected if true.
     /// </value>
     public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
 }
 #nullable restore
 #pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservableProp#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -41,6 +41,14 @@ internal sealed class ObservableAsPropertyAttribute : Attribute
     /// The AccessModifier of the OAPH property, protected if true.
     /// </value>
     public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
 }
 #nullable restore
 #pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservablePropNestedClasses#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -41,6 +41,14 @@ internal sealed class ObservableAsPropertyAttribute : Attribute
     /// The AccessModifier of the OAPH property, protected if true.
     /// </value>
     public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
 }
 #nullable restore
 #pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservablePropertiesWithAttribute#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -41,6 +41,14 @@ internal sealed class ObservableAsPropertyAttribute : Attribute
     /// The AccessModifier of the OAPH property, protected if true.
     /// </value>
     public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
 }
 #nullable restore
 #pragma warning restore

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservablePropertiesWithAttribute#TestNs.TestVM.ObservableAsPropertyFromObservable.g.verified.cs

@@ -20,6 +20,7 @@ public partial class TestVM
 
         /// <inheritdoc cref="_test5Property"/>
         [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+        [global::System.Runtime.Serialization.DataMemberAttribute()]
         [global::System.Text.Json.Serialization.JsonIncludeAttribute()]
         public int Test5Property { get => _test5Property = _test5PropertyHelper?.Value ?? _test5Property; }
 

src/ReactiveUI.SourceGenerator.Tests/OAPH/OAPFromObservableGeneratorTests.FromObservablePropertiesWithAttributeNullableRef#ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute.g.verified.cs

@@ -41,6 +41,14 @@ internal sealed class ObservableAsPropertyAttribute : Attribute
     /// The AccessModifier of the OAPH property, protected if true.
     /// </value>
     public bool UseProtected { get; init; } = false;
+
+    /// <summary>
+    /// Gets the Initial value of the OAPH property.
+    /// </summary>
+    /// <value>
+    /// The initial value of the OAPH property.
+    /// </value>
+    public string? InitialValue { get; init; }
 }
 #nullable restore
 #pragma warning restore