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// 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 more information.
#nullable disable warnings
using System;
using System.Collections.Immutable;
using System.Composition;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Simplification;
using Roslyn.Diagnostics.Analyzers;
namespace Roslyn.Diagnostics.CSharp.Analyzers
{
[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(PreferNullLiteralCodeFixProvider))]
[Shared]
[method: ImportingConstructor]
[method: Obsolete("This exported object must be obtained through the MEF export provider.", error: true)]
public class PreferNullLiteralCodeFixProvider() : CodeFixProvider
{
public override ImmutableArray<string> FixableDiagnosticIds { get; } = ImmutableArray.Create(PreferNullLiteral.Rule.Id);
public override FixAllProvider GetFixAllProvider()
=> WellKnownFixAllProviders.BatchFixer;
public override Task RegisterCodeFixesAsync(CodeFixContext context)
{
foreach (var diagnostic in context.Diagnostics)
{
context.RegisterCodeFix(
CodeAction.Create(
RoslynDiagnosticsAnalyzersResources.PreferNullLiteralCodeFix,
cancellationToken => ReplaceWithNullLiteralAsync(context.Document, diagnostic.Location, cancellationToken),
equivalenceKey: nameof(PreferNullLiteralCodeFixProvider)),
diagnostic);
}
return Task.CompletedTask;
}
private static async Task<Document> ReplaceWithNullLiteralAsync(Document document, Location location, CancellationToken cancellationToken)
{
var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
var syntax = root.FindNode(location.SourceSpan, getInnermostNodeForTie: true);
ExpressionSyntax newSyntax = SyntaxFactory.LiteralExpression(SyntaxKind.NullLiteralExpression);
if (syntax is DefaultExpressionSyntax defaultExpression)
{
var type = defaultExpression.Type;
if (!type.IsKind(SyntaxKind.NullableType) && !type.IsKind(SyntaxKind.PointerType))
{
var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var nullableContext = semanticModel.GetNullableContext(type.SpanStart);
if (nullableContext.AnnotationsEnabled())
{
type = SyntaxFactory.NullableType(type.WithoutTrivia()).WithTriviaFrom(type);
}
}
var castExpression = SyntaxFactory.CastExpression(type, newSyntax.WithTrailingTrivia(defaultExpression.Keyword.TrailingTrivia));
castExpression = castExpression
.WithOpenParenToken(castExpression.OpenParenToken.WithTriviaFrom(defaultExpression.OpenParenToken))
.WithCloseParenToken(castExpression.CloseParenToken.WithLeadingTrivia(defaultExpression.CloseParenToken.LeadingTrivia));
newSyntax = SyntaxFactory.ParenthesizedExpression(castExpression.WithAdditionalAnnotations(Simplifier.Annotation))
.WithAdditionalAnnotations(Simplifier.Annotation);
}
newSyntax = newSyntax.WithTriviaFrom(syntax);
return document.WithSyntaxRoot(root.ReplaceNode(syntax, newSyntax));
}
}
}
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