private async Task <Document> UseDeclarationExpression(Document document, ArgumentSyntax argument, VariableDeclaratorSyntax declarator,
CancellationToken cancellationToken)
{
// get variable declaration
var declaration = declarator.Parent;
// get statement which contains both local declaration statement and method call with out argument
var statement = OutArgumentDeclarationAnalyzer.GetContainingStatement(declaration.Parent);
// remove entire local declaration statement or just single variable declaration
// depending on how many variables are declared within single local declaration statement
var nodeToRemove = declaration.ChildNodes().OfType <VariableDeclaratorSyntax>().Count() > 1 ? declarator : declaration.Parent;
var newStatement = statement.RemoveNode(nodeToRemove, SyntaxRemoveOptions.KeepEndOfLine);
// get variable type
var type = declaration.ChildNodes().First() as TypeSyntax;
// create new Declaration Expression using variable type and declarator
var newDeclarationExpression = SyntaxFactory.DeclarationExpression(type, declarator);
// fix the trivia aroung Declaration Expression
var firstToken = newDeclarationExpression.GetFirstToken();
var leadingTrivia = firstToken.LeadingTrivia;
var trimmedDeclarationExpression = newDeclarationExpression.ReplaceToken(firstToken, firstToken.WithLeadingTrivia(SyntaxTriviaList.Empty));
// get ArgumentSyntax from newStatement which is equivalent to argument from original syntax tree
var newArgument = newStatement.DescendantNodes()
.FirstOrDefault(n => n.IsEquivalentTo(argument));
// replace argument with new version, containing Declaration Expression
newStatement = newStatement.ReplaceNode(newArgument.ChildNodes().First(), trimmedDeclarationExpression);
// get root for current document and replace statement with new version
var root = await document.GetSyntaxRootAsync(cancellationToken);
var newRoot = root.ReplaceNode(statement, newStatement);
// return document with modified syntax
return(document.WithSyntaxRoot(newRoot));
}
public async override Task <IEnumerable <CodeAction> > GetFixesAsync(Document document, TextSpan span, IEnumerable <Diagnostic> diagnostics, CancellationToken cancellationToken)
{
var root = await document.GetSyntaxRootAsync(cancellationToken);
var diagnosticSpan = diagnostics.First().Location.SourceSpan;
var argument = root.FindToken(diagnosticSpan.Start).Parent as ArgumentSyntax;
if (argument == null)
{
return(null);
}
var semanticModel = await document.GetSemanticModelAsync(cancellationToken);
var declarator = OutArgumentDeclarationAnalyzer.GetDeclaration(argument, semanticModel, cancellationToken, out SymbolInfo? info);
if (declarator == null || !info.HasValue)
{
return(Enumerable.Empty <CodeAction>());
}
return(new[] { CodeAction.Create("Use declaration expression", c => UseDeclarationExpression(document, argument, declarator, c)) });
}
