使用Roslyn分析器和修复器对异步方法规范化返回Async结尾

之前写过一篇使用修复器帮助添加头部注释文本的功能,今天使用Roslyn的代码修复器对异步返回方法规范化的功能

实现分析器

首先需要实现分析器,使用RegisterSyntaxNodeAction,分析所有SyntaxKind.MethodDeclaration的语法类型,

[DiagnosticAnalyzer(LanguageNames.CSharp)]
public class AsyncMethodNameAnalyzer : DiagnosticAnalyzer
{
    public const string DiagnosticId = "GEN051";
    private static readonly LocalizableString Title = "将异步方法名改为以Async结尾";
    private static readonly LocalizableString MessageFormat = "将异步方法名改为以Async结尾";
    private static readonly LocalizableString Description = "将异步方法名改为以Async结尾.";
    private const string Category = "Documentation";

    private static readonly DiagnosticDescriptor Rule = new(
    DiagnosticId, Title, MessageFormat, Category,
    DiagnosticSeverity.Warning, isEnabledByDefault: true, description: Description);

    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => [Rule];


    public override void Initialize(AnalysisContext context)
    {
        if (context is null)
            return;
        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
        context.EnableConcurrentExecution();
        context.RegisterSyntaxNodeAction(AnalyzeNode, SyntaxKind.MethodDeclaration);
    }

    // 异步方法名称应该以Async结尾
    private const string AsyncSuffix = "Async";

    private static void AnalyzeNode(SyntaxNodeAnalysisContext context)
    {
        var methodDeclaration = (MethodDeclarationSyntax)context.Node;
        var diagnostic = Diagnostic.Create(Rule, methodDeclaration.Identifier.GetLocation(), methodDeclaration.Identifier.Text);

        //如果方法包含async修饰的情况
        if (methodDeclaration.Modifiers.Any(SyntaxKind.AsyncKeyword))
        {
            if (!methodDeclaration.Identifier.Text.EndsWith(AsyncSuffix, StringComparison.OrdinalIgnoreCase))
            {
                context.ReportDiagnostic(diagnostic);
                return;
            }
        }

        var returnType = methodDeclaration.ReturnType;

        //如果返回类型为Task或者Task<T>,或者ValueTask<T>,ValueTask 则方法名应该以Async结尾
        // 判断返回类型是否为 Task 或 ValueTask
        if (returnType is IdentifierNameSyntax identifierName)
        {
            if (identifierName.Identifier.Text == "Task" || identifierName.Identifier.Text == "ValueTask")
            {
                if (!methodDeclaration.Identifier.Text.EndsWith(AsyncSuffix, StringComparison.OrdinalIgnoreCase))
                {
                    context.ReportDiagnostic(diagnostic);
                    return;
                }
            }
        }
        else if (returnType is GenericNameSyntax genericName && (genericName.Identifier.Text == "Task" || genericName.Identifier.Text == "ValueTask"))
        {
            if (!methodDeclaration.Identifier.Text.EndsWith(AsyncSuffix, StringComparison.OrdinalIgnoreCase))
            {
                context.ReportDiagnostic(diagnostic);
                return;
            }
        }
    }
}

在 Initialize 方法中，注册了一个语法节点操作来处理 MethodDeclarationSyntax 节点,主要是考虑方法是否async关键字标注,或者返回的类型是否是Task或者ValueTask,如果这些条件满足则判断方法名称MethodDeclaration.Identifier是否为Async结尾.如果存在这样的问题那么创建一个诊断报告。

实现修复器

[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(AsyncMethodNameCodeFixProvider))]
[Shared]
internal class AsyncMethodNameCodeFixProvider : CodeFixProvider
{
    public override ImmutableArray<string> FixableDiagnosticIds => [AsyncMethodNameAnalyzer.DiagnosticId];

    public sealed override FixAllProvider GetFixAllProvider() =>
        WellKnownFixAllProviders.BatchFixer;

    private const string Title = "将异步方法名改为以Async结尾";


    public override Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        var diagnostic = context.Diagnostics[0];
        var diagnosticSpan = diagnostic.Location.SourceSpan;

        context.RegisterCodeFix(
            CodeAction.Create(
                title: Title,
                createChangedDocument:
                c =>
                FixDocumentAsync(context.Document, diagnostic, c),
                equivalenceKey: Title),
            diagnostic);

        return Task.CompletedTask;

    }

    private const string AsyncSuffix = "Async";

    private static async Task<Document> FixDocumentAsync(Document document, Diagnostic diagnostic, CancellationToken c)
    {
        var root = await document.GetSyntaxRootAsync(c).ConfigureAwait(false);

        if (root == null)
            return document;

        var node = root.FindNode(diagnostic.Location.SourceSpan);
        var methodDeclaration = (MethodDeclarationSyntax)node;
        var newName = $"{methodDeclaration.Identifier.Text}{AsyncSuffix}";
        var newRoot = root.ReplaceNode(methodDeclaration, methodDeclaration.WithIdentifier(SyntaxFactory.Identifier(newName)));
        return document.WithSyntaxRoot(newRoot);
    }
}

修复器的实现就更加简单了,我们通过诊断信息和Document就可以定位到有问题的方法本身,然后使用WithIdentifier 和SyntaxFactory.Identifier将方法名称修正为正确的值并返回修复的Document即可!