1

Hi everyone,

I'm currently working on a Macro to generate DTO type.
While doing so and to provide a good user experience I try to use Swift-diagnostic to provide error messages and fixit actions.

One of the fixit I'm trying to provide is to ensure that 2 types are identical and if not replace one by the other.

more specifically I use an attached macro of this form :

@ConvertDTOType(from: Int, to: Amount, convert: {Amount(withCents: $0)})
    var amount: Amount

Where "to: TYPE" must be identical to 'amount: TYPE'.

I wrote this fixit :

                 fixIt = [FixIt(
                    message: FixDestTypeMessage(
                        attributeType: destTypeNode.description,
                        propertyType: propertyType.description
                    ),
                    changes: [
                        FixIt.Change.replace(
                            oldNode: Syntax(destTypeNode),
                            newNode: Syntax(propertyType)
                        )
                    ]
                )]

where destTypeNode is the node of the 'to: TYPE' type in the @attribute and propertyType is the type of the property (amount in the previous example).

My problème is that this fixit is greyed out and therefore doesn't work.
However if I switch the 2 values of oldNode and newNode
Then the fixit works be replacing the property type with the attribute type (the opposite of what I want)

Am I missing something here, note that I'm very new with swiftSyntax framework and even newer with swift diagnostic so any help will be appreciated.

2

Your code looks correct in general. Do you have an example project which you can share that reproduces the problem? If so, I can take a look.

3

Thanks for you answer.

The project is open source so you can find the full code here : GitHub - OctoPoulpeStudio/DTOMacro: A Swift Macro that generate DTO object.

However here is a simplified version of the problem, without intermediary function call it's a bit messy because there is few things happening

public struct ConvertDTOMacro: PeerMacro {
    public static func expansion(of node: AttributeSyntax, providingPeersOf declaration: some DeclSyntaxProtocol, in context: some MacroExpansionContext) throws -> [DeclSyntax] {
        guard let variable = declaration.as(VariableDeclSyntax.self) else {return []}
        var result: [Diagnostic] = []
        
        if let convertAttribute = variable.attributes?.filter({filter(attributeNamed: "ConvertDTOType", element: $0)}).first?.as(AttributeSyntax.self)
        {
            if let arguments = convertAttribute.arguments?.as(LabeledExprListSyntax.self),
               let destinationTypeOrigin =  arguments.first(where: { tupleExprElementSyntax in tupleExprElementSyntax.label?.text == "to" })?.expression
            {
                let destinationType = TypeAnnotationSyntax(type: TypeSyntax("\(raw: destinationTypeOrigin)"))
                let propertyType = variable.bindings.first?.typeAnnotation?.as(TypeAnnotationSyntax.self)
                
                if !SNC.compare(propertyType , destinationType) {
                    if let propertyType = variable.bindings.first?.typeAnnotation?.as(TypeAnnotationSyntax.self) {
                        
                        let fixIt = [FixIt(
                            message: FixDestTypeMessage(
                                attributeType: destinationType.type.description,
                                propertyType: propertyType.type.description
                            ),
                            changes: [
                                FixIt.Change.replace(
                                    oldNode: Syntax(destinationType),
                                    newNode: Syntax(propertyType.type)
                                )
                            ]
                        )]
                        
                        let diag = Diagnostic(
                            node: variable,
                            message: DTODiagnostic.DTOConvertFromTypeDontMatchError,
                            fixIts: fixIt
                        )
                        result.append(diag)
                    }
                }
                for diag in result {
                    context.diagnose(diag)
                }
                
            }
        }
        return []
    }
    
    internal static func filter(attributeNamed name:String, element: AttributeListSyntax.Element) -> Bool {
        guard let attribute = element.as(AttributeSyntax.self) else { return false}
        return attribute.attributeName.as(IdentifierTypeSyntax.self)?.name.text == name
    }
}

And here is the line with error in a struct :

    @ConvertDTOType(from: Int, to: Amount, convert: {Amount(withCents: $0)})
    var status: State

I have the felling that this is because destinationType is kind of a new node created out of the data from the attribute

let destinationType = TypeAnnotationSyntax(type: TypeSyntax("\(raw: destinationTypeOrigin)"))

However I tried with the orignal node and I had the same problem...

And here is the error message with the greyed out replacement fixit

Screenshot 2023-08-15 at 13.41.30
Screenshot 2023-08-15 at 13.41.301140×200 39.3 KB

Thanks a lot for your help.