private async Task UpdateAttributeAsync()

in src/Microsoft.VisualStudio.SDK.Analyzers.CodeFixes/VSSDK002PackageRegistrationMatchesBaseTypeCodeFix.cs [47:81]
29 lines of code
6 McCabe index (conditional complexity)

        private async Task<Document> UpdateAttributeAsync(CodeFixContext context, Diagnostic diagnostic, CancellationToken cancellationToken)
        {
            bool isAsyncPackage = diagnostic.Properties[VSSDK002PackageRegistrationMatchesBaseTypeAnalyzer.BaseTypeDiagnosticPropertyName] == Types.AsyncPackage.TypeName;
            LiteralExpressionSyntax appropriateArgument = SyntaxFactory.LiteralExpression(isAsyncPackage ? SyntaxKind.TrueLiteralExpression : SyntaxKind.FalseLiteralExpression);

            SyntaxNode root = await context.Document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
            switch (root.FindNode(diagnostic.Location.SourceSpan))
            {
                case AttributeSyntax packageRegistrationSyntax:
                    // We need to add an argument to this attribute
                    root = root.ReplaceNode(
                        packageRegistrationSyntax,
                        packageRegistrationSyntax.AddArgumentListArguments(
                            SyntaxFactory.AttributeArgument(appropriateArgument).WithNameEquals(SyntaxFactory.NameEquals(Types.PackageRegistrationAttribute.AllowsBackgroundLoading))));
                    break;
                case AttributeArgumentSyntax allowBackgroundLoadingSyntax:
                    if (isAsyncPackage)
                    {
                        // We need to update this argument on the attribute.
                        AttributeSyntax originalAttribute = allowBackgroundLoadingSyntax.FirstAncestorOrSelf<AttributeSyntax>();
                        root = root.ReplaceNode(allowBackgroundLoadingSyntax, allowBackgroundLoadingSyntax.WithExpression(appropriateArgument));
                    }
                    else
                    {
                        // Let's just remove it since false is its default value.
                        root = root.RemoveNode(allowBackgroundLoadingSyntax, SyntaxRemoveOptions.KeepNoTrivia);
                    }

                    break;
                case SyntaxNode node:
                    throw new InvalidOperationException("Unexpected syntax type: " + node.GetType().Name);
            }

            return context.Document.WithSyntaxRoot(root);
        }