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[Blazor] Add analyzer to warn when SupplyParameterFromForm properties have non-default initializers (#63110)
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‎src/Components/Analyzers/src/ComponentFacts.cs‎

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@@ -87,6 +87,57 @@ public static bool IsCascadingParameter(ComponentSymbols symbols, IPropertySymbo
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return property.GetAttributes().Any(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, symbols.CascadingParameterAttribute));
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}
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public static bool IsSupplyParameterFromForm(ComponentSymbols symbols, IPropertySymbol property)
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{
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if (symbols == null)
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{
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throw new ArgumentNullException(nameof(symbols));
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}
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if (property == null)
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{
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throw new ArgumentNullException(nameof(property));
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}
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if (symbols.SupplyParameterFromFormAttribute == null)
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{
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return false;
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}
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return property.GetAttributes().Any(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, symbols.SupplyParameterFromFormAttribute));
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}
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public static bool IsComponentBase(ComponentSymbols symbols, INamedTypeSymbol type)
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{
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if (symbols is null)
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{
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throw new ArgumentNullException(nameof(symbols));
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}
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if (type is null)
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{
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throw new ArgumentNullException(nameof(type));
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}
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if (symbols.ComponentBaseType == null)
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{
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return false;
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}
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// Check if the type inherits from ComponentBase
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var current = type.BaseType;
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while (current != null)
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{
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if (SymbolEqualityComparer.Default.Equals(current, symbols.ComponentBaseType))
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{
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return true;
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}
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current = current.BaseType;
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}
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return false;
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}
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public static bool IsComponent(ComponentSymbols symbols, Compilation compilation, INamedTypeSymbol type)
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{
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if (symbols is null)

‎src/Components/Analyzers/src/ComponentSymbols.cs‎

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Original file line numberDiff line numberDiff line change
@@ -47,9 +47,15 @@ public static bool TryCreate(Compilation compilation, out ComponentSymbols symbo
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var parameterCaptureUnmatchedValuesRuntimeType = dictionary.Construct(@string, @object);
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// Try to get optional symbols for SupplyParameterFromForm analyzer
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var supplyParameterFromFormAttribute = compilation.GetTypeByMetadataName(ComponentsApi.SupplyParameterFromFormAttribute.MetadataName);
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var componentBaseType = compilation.GetTypeByMetadataName(ComponentsApi.ComponentBase.MetadataName);
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symbols = new ComponentSymbols(
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parameterAttribute,
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cascadingParameterAttribute,
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supplyParameterFromFormAttribute,
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componentBaseType,
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parameterCaptureUnmatchedValuesRuntimeType,
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icomponentType);
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return true;
@@ -58,11 +64,15 @@ public static bool TryCreate(Compilation compilation, out ComponentSymbols symbo
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private ComponentSymbols(
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INamedTypeSymbol parameterAttribute,
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INamedTypeSymbol cascadingParameterAttribute,
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INamedTypeSymbol supplyParameterFromFormAttribute,
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INamedTypeSymbol componentBaseType,
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INamedTypeSymbol parameterCaptureUnmatchedValuesRuntimeType,
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INamedTypeSymbol icomponentType)
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{
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ParameterAttribute = parameterAttribute;
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CascadingParameterAttribute = cascadingParameterAttribute;
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SupplyParameterFromFormAttribute = supplyParameterFromFormAttribute; // Can be null
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ComponentBaseType = componentBaseType; // Can be null
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ParameterCaptureUnmatchedValuesRuntimeType = parameterCaptureUnmatchedValuesRuntimeType;
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IComponentType = icomponentType;
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}
@@ -74,5 +84,9 @@ private ComponentSymbols(
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public INamedTypeSymbol CascadingParameterAttribute { get; }
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public INamedTypeSymbol SupplyParameterFromFormAttribute { get; } // Can be null if not available
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public INamedTypeSymbol ComponentBaseType { get; } // Can be null if not available
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public INamedTypeSymbol IComponentType { get; }
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}

‎src/Components/Analyzers/src/ComponentsApi.cs‎

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Original file line numberDiff line numberDiff line change
@@ -23,6 +23,18 @@ public static class CascadingParameterAttribute
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public const string MetadataName = FullTypeName;
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}
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public static class SupplyParameterFromFormAttribute
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{
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public const string FullTypeName = "Microsoft.AspNetCore.Components.SupplyParameterFromFormAttribute";
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public const string MetadataName = FullTypeName;
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}
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public static class ComponentBase
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{
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public const string FullTypeName = "Microsoft.AspNetCore.Components.ComponentBase";
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public const string MetadataName = FullTypeName;
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}
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public static class IComponent
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{
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public const string FullTypeName = "Microsoft.AspNetCore.Components.IComponent";

‎src/Components/Analyzers/src/DiagnosticDescriptors.cs‎

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@@ -74,4 +74,13 @@ internal static class DiagnosticDescriptors
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Usage,
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DiagnosticSeverity.Warning,
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isEnabledByDefault: true);
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public static readonly DiagnosticDescriptor SupplyParameterFromFormShouldNotHavePropertyInitializer = new(
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"BL0008",
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CreateLocalizableResourceString(nameof(Resources.SupplyParameterFromFormShouldNotHavePropertyInitializer_Title)),
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CreateLocalizableResourceString(nameof(Resources.SupplyParameterFromFormShouldNotHavePropertyInitializer_Format)),
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Usage,
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DiagnosticSeverity.Warning,
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isEnabledByDefault: true,
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description: CreateLocalizableResourceString(nameof(Resources.SupplyParameterFromFormShouldNotHavePropertyInitializer_Description)));
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}

‎src/Components/Analyzers/src/Resources.resx‎

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@@ -180,4 +180,13 @@
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<data name="ComponentParametersShouldBeAutoProperties_Title" xml:space="preserve">
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<value>Component parameters should be auto properties</value>
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</data>
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<data name="SupplyParameterFromFormShouldNotHavePropertyInitializer_Description" xml:space="preserve">
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<value>The value of a property decorated with [SupplyParameterFromForm] and initialized with a property initializer can be overwritten with null when the component receives parameters. To ensure the initialized value is not overwritten, move the initialization to a component lifecycle method like OnInitialized or OnInitializedAsync</value>
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</data>
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<data name="SupplyParameterFromFormShouldNotHavePropertyInitializer_Format" xml:space="preserve">
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<value>Property '{0}' has [SupplyParameterFromForm] and a property initializer. This can be overwritten with null during form posts.</value>
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</data>
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<data name="SupplyParameterFromFormShouldNotHavePropertyInitializer_Title" xml:space="preserve">
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<value>Property with [SupplyParameterFromForm] should not have initializer</value>
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</data>
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</root>

‎src/Components/Analyzers/src/SupplyParameterFromFormAnalyzer.cs‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,101 @@
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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using System.Collections.Immutable;
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using System.Linq;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.CSharp;
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using Microsoft.CodeAnalysis.CSharp.Syntax;
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using Microsoft.CodeAnalysis.Diagnostics;
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#nullable enable
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namespace Microsoft.AspNetCore.Components.Analyzers;
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[DiagnosticAnalyzer(LanguageNames.CSharp)]
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public sealed class SupplyParameterFromFormAnalyzer : DiagnosticAnalyzer
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{
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public SupplyParameterFromFormAnalyzer()
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{
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SupportedDiagnostics = ImmutableArray.Create(
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DiagnosticDescriptors.SupplyParameterFromFormShouldNotHavePropertyInitializer);
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}
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public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; }
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public override void Initialize(AnalysisContext context)
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{
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context.EnableConcurrentExecution();
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context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.Analyze | GeneratedCodeAnalysisFlags.ReportDiagnostics);
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context.RegisterCompilationStartAction(context =>
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{
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if (!ComponentSymbols.TryCreate(context.Compilation, out var symbols))
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{
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// Types we need are not defined.
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return;
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}
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context.RegisterSyntaxNodeAction(context =>
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{
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var propertyDeclaration = (PropertyDeclarationSyntax)context.Node;
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// Check if property has an initializer
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if (propertyDeclaration.Initializer == null)
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{
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return;
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}
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// Ignore initializers that set to default values (null, default, etc.)
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if (IsDefaultValueInitializer(propertyDeclaration.Initializer.Value))
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{
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return;
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}
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var propertySymbol = context.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
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if (propertySymbol == null)
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{
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return;
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}
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// Check if property has [SupplyParameterFromForm] attribute
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if (!ComponentFacts.IsSupplyParameterFromForm(symbols, propertySymbol))
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{
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return;
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}
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// Check if the containing type inherits from ComponentBase
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var containingType = propertySymbol.ContainingType;
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if (!ComponentFacts.IsComponentBase(symbols, containingType))
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{
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return;
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}
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var propertyLocation = propertySymbol.Locations.FirstOrDefault();
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if (propertyLocation != null)
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{
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context.ReportDiagnostic(Diagnostic.Create(
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DiagnosticDescriptors.SupplyParameterFromFormShouldNotHavePropertyInitializer,
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propertyLocation,
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propertySymbol.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat)));
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}
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}, SyntaxKind.PropertyDeclaration);
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});
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}
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private static bool IsDefaultValueInitializer(ExpressionSyntax expression)
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{
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return expression switch
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{
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// null
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LiteralExpressionSyntax { Token.ValueText: "null" } => true,
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// null!
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PostfixUnaryExpressionSyntax { Operand: LiteralExpressionSyntax { Token.ValueText: "null" }, OperatorToken.ValueText: "!" } => true,
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// default
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LiteralExpressionSyntax literal when literal.Token.IsKind(SyntaxKind.DefaultKeyword) => true,
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// default!
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PostfixUnaryExpressionSyntax { Operand: LiteralExpressionSyntax literal, OperatorToken.ValueText: "!" }
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when literal.Token.IsKind(SyntaxKind.DefaultKeyword) => true,
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_ => false
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};
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}
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}

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