internal override SyntaxNode OrchestrateMutation(MethodDeclarationSyntax node, MutationContext context)
{
var mutatedNode = (MethodDeclarationSyntax)context.MutateNodeAndChildren(node);
if (mutatedNode.Body == null)
{
return(mutatedNode);
}
// If method return type is void skip the node
if (mutatedNode.ReturnType is PredefinedTypeSyntax predefinedType &&
predefinedType.Keyword.IsKind(SyntaxKind.VoidKeyword))
{
return(mutatedNode);
}
if (node.Body.ContainsNodeThatVerifies(x => x.IsKind(SyntaxKind.YieldReturnStatement), false))
{
// not need to add yield return at the end of an enumeration method
return(mutatedNode);
}
if (mutatedNode.Body.Statements.Last().Kind() == SyntaxKind.ReturnStatement)
{
return(mutatedNode);
}
var returnType = mutatedNode.ReturnType;
// the GenericNameSyntax node can be encapsulated by QualifiedNameSyntax nodes
var genericReturn = returnType.DescendantNodesAndSelf().OfType <GenericNameSyntax>().FirstOrDefault();
if (mutatedNode.Modifiers.Any(x => x.IsKind(SyntaxKind.AsyncKeyword)))
{
if (genericReturn != null)
{
// if the method is async and returns a generic task, make the return default return the underlying type
returnType = genericReturn.TypeArgumentList.Arguments.First();
}
else
{
// if the method is async but returns a non-generic task, don't add the return default
return(mutatedNode);
}
}
var newBody = mutatedNode.Body.AddStatements(
MutantPlacer.AnnotateHelper(
SyntaxFactory.ReturnStatement(SyntaxFactory.DefaultExpression(returnType).WithLeadingTrivia(SyntaxFactory.Space))));
mutatedNode = mutatedNode.ReplaceNode(mutatedNode.Body, newBody);
return(mutatedNode);
}