DoNotRemoveOriginalExceptionFromThrowStatementFixer.cs

using System.Collections.Immutable;
using System.Composition;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Formatting;

namespace Meziantou.Analyzer.Rules;

[ExportCodeFixProvider(LanguageNames.CSharp), Shared]
public sealed class DoNotRemoveOriginalExceptionFromThrowStatementFixer : CodeFixProvider
{
    public override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(RuleIdentifiers.DoNotRemoveOriginalExceptionFromThrowStatement);

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

    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
        var nodeToFix = root?.FindNode(context.Span, getInnermostNodeForTie: true);
        if (nodeToFix is null)
            return;

        var title = "Throw original exception";
        var codeAction = CodeAction.Create(
            title,
            ct => Fix(context.Document, nodeToFix, ct),
            equivalenceKey: title);

        context.RegisterCodeFix(codeAction, context.Diagnostics);
    }

    private static async Task<Document> Fix(Document document, SyntaxNode nodeToFix, CancellationToken cancellationToken)
    {
        var editor = await DocumentEditor.CreateAsync(document, cancellationToken).ConfigureAwait(false);

        var syntax = (ThrowStatementSyntax)nodeToFix;
        if (syntax is null)
            return document;

        editor.ReplaceNode(syntax, syntax.WithExpression(null).WithAdditionalAnnotations(Formatter.Annotation));
        return editor.GetChangedDocument();
    }
}