Feature Add OAPH From Observable method

src/ReactiveUI.SourceGenerators.Execute/TestViewModel.cs

@@ -34,6 +34,7 @@ public partial class TestViewModel : ReactiveObject
     public TestViewModel()
     {
         InitializeCommands();
+        InitializeOAPH();
 
         Console.Out.WriteLine(Test1Command);
         Console.Out.WriteLine(Test2Command);
@@ -97,6 +98,15 @@ public TestViewModel()
     public IObservable<bool> CanExecuteTest1 => Observable.Return(true);
 #pragma warning restore CA1822 // Mark members as static
 
+    /// <summary>
+    /// Gets observables as property test.
+    /// </summary>
+    /// <returns>
+    /// Observable of double.
+    /// </returns>
+    [ObservableAsProperty(PropertyName = "MyReadOnlyProperty")]
+    public IObservable<double> ObservableAsPropertyTest() => Observable.Return(10.0);
+
     /// <summary>
     /// Test1s this instance.
     /// </summary>

src/ReactiveUI.SourceGenerators/AnalyzerReleases.Shipped.md

@@ -23,3 +23,4 @@ RXUISG0013 | ReactiveUI.SourceGenerators.ObservableAsPropertyGenerator | Error |
 RXUISG0014 | ReactiveUI.SourceGenerators.ObservableAsPropertyGenerator | Error | See https://www.reactiveui.net/errors/RXUISG0014
 RXUISG0015 | ReactiveUI.SourceGenerators.ReactiveGenerator | Error | See https://www.reactiveui.net/errors/RXUISG0015
 RXUISG0016 | ReactiveUI.SourceGenerators.PropertyToReactiveFieldCodeFixProvider | Info | See https://www.reactiveui.net/errors/RXUISG0016
+RXUISG0017 | ReactiveUI.SourceGenerators.ObservableAsPropertyFromObservableGenerator | Error | See https://www.reactiveui.net/errors/RXUISG0017

src/ReactiveUI.SourceGenerators/Diagnostics/DiagnosticDescriptors.cs

@@ -264,4 +264,17 @@ internal static class DiagnosticDescriptors
         isEnabledByDefault: true,
         description: "Used to create a Read Write INPC Reactive Property for ReactiveUI, annotated with [Reactive].",
         helpLinkUri: "https://www.reactiveui.net/errors/RXUISG0016");
+
+    /// <summary>
+    /// The observable as property method has parameters error.
+    /// </summary>
+    public static readonly DiagnosticDescriptor ObservableAsPropertyMethodHasParametersError = new DiagnosticDescriptor(
+        id: "RXUISG0017",
+        title: "Invalid generated property declaration",
+        messageFormat: "The method {0} cannot be used to generate an observable As property, as it has parameters",
+        category: typeof(ObservableAsPropertyFromObservableGenerator).FullName,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "The method annotated with [ObservableAsProperty] cannot currently initialize methods with parameters.",
+        helpLinkUri: "https://www.reactiveui.net/errors/RXUISG0017");
 }

src/ReactiveUI.SourceGenerators/Diagnostics/Suppressions/OAPHMethodDoesNotNeedToBeStaticDiagnosticSuppressor.cs

@@ -0,0 +1,51 @@
+// Copyright (c) 2024 .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.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using ReactiveUI.SourceGenerators.Extensions;
+using static ReactiveUI.SourceGenerators.Diagnostics.SuppressionDescriptors;
+
+namespace ReactiveUI.SourceGenerators.Diagnostics.Suppressions;
+
+/// <summary>
+/// ReactiveCommand Attribute With Field Or Property Target Diagnostic Suppressor.
+/// </summary>
+/// <seealso cref="DiagnosticSuppressor" />
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class OAPHMethodDoesNotNeedToBeStaticDiagnosticSuppressor : DiagnosticSuppressor
+{
+    /// <inheritdoc/>
+    public override ImmutableArray<SuppressionDescriptor> SupportedSuppressions => ImmutableArray.Create(ReactiveCommandDoesNotAccessInstanceData);
+
+    /// <inheritdoc/>
+    public override void ReportSuppressions(SuppressionAnalysisContext context)
+    {
+        foreach (var diagnostic in context.ReportedDiagnostics)
+        {
+            var syntaxNode = diagnostic.Location.SourceTree?.GetRoot(context.CancellationToken).FindNode(diagnostic.Location.SourceSpan);
+
+            // Check that the target is a method declaration, which is the case we're looking for
+            if (syntaxNode is MethodDeclarationSyntax methodDeclaration)
+            {
+                var semanticModel = context.GetSemanticModel(syntaxNode.SyntaxTree);
+
+                // Get the method symbol from the first variable declaration
+                ISymbol? declaredSymbol = semanticModel.GetDeclaredSymbol(methodDeclaration, context.CancellationToken);
+
+                // Check if the method is using [ObservableAsProperty], in which case we should suppress the warning
+                if (declaredSymbol is IMethodSymbol methodSymbol &&
+                    semanticModel.Compilation.GetTypeByMetadataName("ReactiveUI.SourceGenerators.ObservableAsPropertyAttribute") is INamedTypeSymbol oaphSymbol &&
+                    methodSymbol.HasAttributeWithType(oaphSymbol))
+                {
+                    context.ReportSuppression(Suppression.Create(ReactiveCommandDoesNotAccessInstanceData, diagnostic));
+                }
+            }
+        }
+    }
+}

src/ReactiveUI.SourceGenerators/Diagnostics/Suppressions/ReactiveCommandMethodDoesNotNeedToBeStaticDiagnosticSuppressor.cs

@@ -11,40 +11,39 @@
 using ReactiveUI.SourceGenerators.Extensions;
 using static ReactiveUI.SourceGenerators.Diagnostics.SuppressionDescriptors;
 
-namespace ReactiveUI.SourceGenerators.Diagnostics.Suppressions
+namespace ReactiveUI.SourceGenerators.Diagnostics.Suppressions;
+
+/// <summary>
+/// ReactiveCommand Attribute With Field Or Property Target Diagnostic Suppressor.
+/// </summary>
+/// <seealso cref="DiagnosticSuppressor" />
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class ReactiveCommandMethodDoesNotNeedToBeStaticDiagnosticSuppressor : DiagnosticSuppressor
 {
-    /// <summary>
-    /// ReactiveCommand Attribute With Field Or Property Target Diagnostic Suppressor.
-    /// </summary>
-    /// <seealso cref="DiagnosticSuppressor" />
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
-    public sealed class ReactiveCommandMethodDoesNotNeedToBeStaticDiagnosticSuppressor : DiagnosticSuppressor
-    {
-        /// <inheritdoc/>
-        public override ImmutableArray<SuppressionDescriptor> SupportedSuppressions => ImmutableArray.Create(ReactiveCommandDoesNotAccessInstanceData);
+    /// <inheritdoc/>
+    public override ImmutableArray<SuppressionDescriptor> SupportedSuppressions => ImmutableArray.Create(ReactiveCommandDoesNotAccessInstanceData);
 
-        /// <inheritdoc/>
-        public override void ReportSuppressions(SuppressionAnalysisContext context)
+    /// <inheritdoc/>
+    public override void ReportSuppressions(SuppressionAnalysisContext context)
+    {
+        foreach (var diagnostic in context.ReportedDiagnostics)
         {
-            foreach (var diagnostic in context.ReportedDiagnostics)
-            {
-                var syntaxNode = diagnostic.Location.SourceTree?.GetRoot(context.CancellationToken).FindNode(diagnostic.Location.SourceSpan);
+            var syntaxNode = diagnostic.Location.SourceTree?.GetRoot(context.CancellationToken).FindNode(diagnostic.Location.SourceSpan);
 
-                // Check that the target is a method declaration, which is the case we're looking for
-                if (syntaxNode is MethodDeclarationSyntax methodDeclaration)
-                {
-                    var semanticModel = context.GetSemanticModel(syntaxNode.SyntaxTree);
+            // Check that the target is a method declaration, which is the case we're looking for
+            if (syntaxNode is MethodDeclarationSyntax methodDeclaration)
+            {
+                var semanticModel = context.GetSemanticModel(syntaxNode.SyntaxTree);
 
-                    // Get the method symbol from the first variable declaration
-                    ISymbol? declaredSymbol = semanticModel.GetDeclaredSymbol(methodDeclaration, context.CancellationToken);
+                // Get the method symbol from the first variable declaration
+                ISymbol? declaredSymbol = semanticModel.GetDeclaredSymbol(methodDeclaration, context.CancellationToken);
 
-                    // Check if the method is using [ReactiveCommand], in which case we should suppress the warning
-                    if (declaredSymbol is IMethodSymbol methodSymbol &&
-                        semanticModel.Compilation.GetTypeByMetadataName("ReactiveUI.SourceGenerators.ReactiveCommandAttribute") is INamedTypeSymbol reactiveCommandSymbol &&
-                        methodSymbol.HasAttributeWithType(reactiveCommandSymbol))
-                    {
-                        context.ReportSuppression(Suppression.Create(ReactiveCommandDoesNotAccessInstanceData, diagnostic));
-                    }
+                // Check if the method is using [ReactiveCommand], in which case we should suppress the warning
+                if (declaredSymbol is IMethodSymbol methodSymbol &&
+                    semanticModel.Compilation.GetTypeByMetadataName("ReactiveUI.SourceGenerators.ReactiveCommandAttribute") is INamedTypeSymbol reactiveCommandSymbol &&
+                    methodSymbol.HasAttributeWithType(reactiveCommandSymbol))
+                {
+                    context.ReportSuppression(Suppression.Create(ReactiveCommandDoesNotAccessInstanceData, diagnostic));
                 }
             }
         }

src/ReactiveUI.SourceGenerators/Helpers/AttributeDefinitions.cs

@@ -3,6 +3,8 @@
 // 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;
+
 namespace ReactiveUI.SourceGenerators.Helpers;
 
 internal static class AttributeDefinitions
@@ -48,7 +50,7 @@ namespace ReactiveUI.SourceGenerators;
 /// ReativeCommandAttribute.
 /// </summary>
 /// <seealso cref="Attribute" />
-[global::System.CodeDom.Compiler.GeneratedCode("ReactiveUI.SourceGenerators.IViewForGenerator", "1.1.0.0")]
+[global::System.CodeDom.Compiler.GeneratedCode("ReactiveUI.SourceGenerators.ReactiveCommandGenerator", "1.1.0.0")]
 [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
 public sealed class ReactiveCommandAttribute : Attribute
 {
@@ -81,7 +83,7 @@ namespace ReactiveUI.SourceGenerators;
 /// ReactiveAttribute.
 /// </summary>
 /// <seealso cref="Attribute" />
-[global::System.CodeDom.Compiler.GeneratedCode("ReactiveUI.SourceGenerators.IViewForGenerator", "1.1.0.0")]
+[global::System.CodeDom.Compiler.GeneratedCode("ReactiveUI.SourceGenerators.ReactiveGenerator", "1.1.0.0")]
 [AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
 public sealed class ReactiveAttribute : Attribute;
 #nullable restore
@@ -105,9 +107,18 @@ namespace ReactiveUI.SourceGenerators;
 /// ReactivePropertyAttribute.
 /// </summary>
 /// <seealso cref="Attribute" />
-[global::System.CodeDom.Compiler.GeneratedCode("ReactiveUI.SourceGenerators.IViewForGenerator", "1.1.0.0")]
-[AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
-public sealed class ObservableAsPropertyAttribute : Attribute;
+[global::System.CodeDom.Compiler.GeneratedCode("ReactiveUI.SourceGenerators.ObservableAsPropertyGenerator", "1.1.0.0")]
+[AttributeUsage(AttributeTargets.Field | AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+public sealed class ObservableAsPropertyAttribute : Attribute
+{
+    /// <summary>
+    /// Gets the name of the property.
+    /// </summary>
+    /// <value>
+    /// The name of the property.
+    /// </value>
+    public string? PropertyName { get; init; }
+}
 #nullable restore
 #pragma warning restore
 """;

src/ReactiveUI.SourceGenerators/ObservableAsProperty/Models/ObservableMethodInfo.cs

@@ -0,0 +1,22 @@
+// Copyright (c) 2024 .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 Microsoft.CodeAnalysis;
+using ReactiveUI.SourceGenerators.Helpers;
+
+namespace ReactiveUI.SourceGenerators.ObservableAsProperty.Models
+{
+    internal record ObservableMethodInfo(
+    string MethodName,
+    ITypeSymbol MethodReturnType,
+    ITypeSymbol? ArgumentType,
+    string PropertyName,
+    EquatableArray<AttributeInfo> ForwardedPropertyAttributes)
+    {
+        public string GetObservableTypeText() => MethodReturnType is not INamedTypeSymbol typeSymbol
+                ? string.Empty
+                : typeSymbol.TypeArguments[0].ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
+    }
+}