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[Blazor] Implement property analyzer for [PersistentState] attribute (#63236)
* The analyzer will warn when you use an initializer on the property with a non-default value, as it will be overwritten.
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7 files changed

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7 files changed

+434
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‎src/Components/Analyzers/src/ComponentFacts.cs

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -107,6 +107,26 @@ public static bool IsSupplyParameterFromForm(ComponentSymbols symbols, IProperty
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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 IsPersistentState(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.PersistentStateAttribute == 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.PersistentStateAttribute));
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}
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110130
public static bool IsComponentBase(ComponentSymbols symbols, INamedTypeSymbol type)
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{
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if (symbols is null)

‎src/Components/Analyzers/src/ComponentSymbols.cs

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -47,14 +47,16 @@ 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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// Try to get optional symbols for SupplyParameterFromForm and PersistentState analyzers
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var supplyParameterFromFormAttribute = compilation.GetTypeByMetadataName(ComponentsApi.SupplyParameterFromFormAttribute.MetadataName);
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var persistentStateAttribute = compilation.GetTypeByMetadataName(ComponentsApi.PersistentStateAttribute.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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persistentStateAttribute,
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componentBaseType,
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parameterCaptureUnmatchedValuesRuntimeType,
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icomponentType);
@@ -65,13 +67,15 @@ private ComponentSymbols(
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INamedTypeSymbol parameterAttribute,
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INamedTypeSymbol cascadingParameterAttribute,
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INamedTypeSymbol supplyParameterFromFormAttribute,
70+
INamedTypeSymbol persistentStateAttribute,
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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
78+
PersistentStateAttribute = persistentStateAttribute; // Can be null
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ComponentBaseType = componentBaseType; // Can be null
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ParameterCaptureUnmatchedValuesRuntimeType = parameterCaptureUnmatchedValuesRuntimeType;
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IComponentType = icomponentType;
@@ -86,6 +90,8 @@ private ComponentSymbols(
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public INamedTypeSymbol SupplyParameterFromFormAttribute { get; } // Can be null if not available
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93+
public INamedTypeSymbol PersistentStateAttribute { get; } // Can be null if not available
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8995
public INamedTypeSymbol ComponentBaseType { get; } // Can be null if not available
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public INamedTypeSymbol IComponentType { get; }

‎src/Components/Analyzers/src/ComponentsApi.cs

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -35,6 +35,12 @@ public static class ComponentBase
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public const string MetadataName = FullTypeName;
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}
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public static class PersistentStateAttribute
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{
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public const string FullTypeName = "Microsoft.AspNetCore.Components.PersistentStateAttribute";
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public const string MetadataName = FullTypeName;
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}
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3844
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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Original file line numberDiff line numberDiff line change
@@ -83,4 +83,13 @@ internal static class DiagnosticDescriptors
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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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public static readonly DiagnosticDescriptor PersistentStateShouldNotHavePropertyInitializer = new(
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"BL0009",
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CreateLocalizableResourceString(nameof(Resources.PersistentStateShouldNotHavePropertyInitializer_Title)),
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CreateLocalizableResourceString(nameof(Resources.PersistentStateShouldNotHavePropertyInitializer_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.PersistentStateShouldNotHavePropertyInitializer_Description)));
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}

‎src/Components/Analyzers/src/PersistentStateAnalyzer.cs

Lines changed: 101 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,101 @@
1+
// 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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4+
using System.Collections.Immutable;
5+
using System.Linq;
6+
using Microsoft.CodeAnalysis;
7+
using Microsoft.CodeAnalysis.CSharp;
8+
using Microsoft.CodeAnalysis.CSharp.Syntax;
9+
using Microsoft.CodeAnalysis.Diagnostics;
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11+
#nullable enable
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namespace Microsoft.AspNetCore.Components.Analyzers;
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15+
[DiagnosticAnalyzer(LanguageNames.CSharp)]
16+
public sealed class PersistentStateAnalyzer : DiagnosticAnalyzer
17+
{
18+
public PersistentStateAnalyzer()
19+
{
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SupportedDiagnostics = ImmutableArray.Create(
21+
DiagnosticDescriptors.PersistentStateShouldNotHavePropertyInitializer);
22+
}
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public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; }
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26+
public override void Initialize(AnalysisContext context)
27+
{
28+
context.EnableConcurrentExecution();
29+
context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.Analyze | GeneratedCodeAnalysisFlags.ReportDiagnostics);
30+
context.RegisterCompilationStartAction(context =>
31+
{
32+
if (!ComponentSymbols.TryCreate(context.Compilation, out var symbols))
33+
{
34+
// Types we need are not defined.
35+
return;
36+
}
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38+
context.RegisterSyntaxNodeAction(context =>
39+
{
40+
var propertyDeclaration = (PropertyDeclarationSyntax)context.Node;
41+
42+
// Check if property has an initializer
43+
if (propertyDeclaration.Initializer == null)
44+
{
45+
return;
46+
}
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48+
// Ignore initializers that set to default values (null, default, etc.)
49+
if (IsDefaultValueInitializer(propertyDeclaration.Initializer.Value))
50+
{
51+
return;
52+
}
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54+
var propertySymbol = context.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
55+
if (propertySymbol == null)
56+
{
57+
return;
58+
}
59+
60+
// Check if property has [PersistentState] attribute
61+
if (!ComponentFacts.IsPersistentState(symbols, propertySymbol))
62+
{
63+
return;
64+
}
65+
66+
// Check if the containing type inherits from ComponentBase
67+
var containingType = propertySymbol.ContainingType;
68+
if (!ComponentFacts.IsComponentBase(symbols, containingType))
69+
{
70+
return;
71+
}
72+
73+
var propertyLocation = propertySymbol.Locations.FirstOrDefault();
74+
if (propertyLocation != null)
75+
{
76+
context.ReportDiagnostic(Diagnostic.Create(
77+
DiagnosticDescriptors.PersistentStateShouldNotHavePropertyInitializer,
78+
propertyLocation,
79+
propertySymbol.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat)));
80+
}
81+
}, SyntaxKind.PropertyDeclaration);
82+
});
83+
}
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85+
private static bool IsDefaultValueInitializer(ExpressionSyntax expression)
86+
{
87+
return expression switch
88+
{
89+
// null
90+
LiteralExpressionSyntax { Token.ValueText: "null" } => true,
91+
// null!
92+
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,
95+
// default!
96+
PostfixUnaryExpressionSyntax { Operand: LiteralExpressionSyntax literal, OperatorToken.ValueText: "!" }
97+
when literal.Token.IsKind(SyntaxKind.DefaultKeyword) => true,
98+
_ => false
99+
};
100+
}
101+
}

‎src/Components/Analyzers/src/Resources.resx

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Original file line numberDiff line numberDiff line change
@@ -189,4 +189,13 @@
189189
<data name="SupplyParameterFromFormShouldNotHavePropertyInitializer_Title" xml:space="preserve">
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<value>Property with [SupplyParameterFromForm] should not have initializer</value>
191191
</data>
192+
<data name="PersistentStateShouldNotHavePropertyInitializer_Description" xml:space="preserve">
193+
<value>The value of a property decorated with [PersistentState] and initialized with a property initializer can be overwritten 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>
194+
</data>
195+
<data name="PersistentStateShouldNotHavePropertyInitializer_Format" xml:space="preserve">
196+
<value>Property '{0}' has [PersistentState] and a property initializer. This can be overwritten during parameter binding.</value>
197+
</data>
198+
<data name="PersistentStateShouldNotHavePropertyInitializer_Title" xml:space="preserve">
199+
<value>Property with [PersistentState] should not have initializer</value>
200+
</data>
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</root>

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