Weird compilation error on Route parsing

[rcasula]

Hi, I was trying to model an existing API but I'm encountering a problem.

Example:

This is one of the urls: BASE_URL/somepath/SOME_STRING_VAR/ANOTHER_STRING_VAR.
The method is POST and it has a String body.

I was trying to model it like this:

enum SiteRoute {
    case somepath(var1: String, var2: String, body: String)
}
... 
let router = OneOf {
    Route(.case(SiteRoute.somepath)) {
        Method.post
        Path { 
            "someroute"
            Parse(.string)
            Parse(.string)
        }
        Body(?) // I can't figure out what to put here.
    }
}

If I define the model like this, instead:

enum SiteRoute {
    case somepath(var1: String, var2: String, body: SomeModel)
}
... 
let router = OneOf {
    Route(.case(SiteRoute.somepath)) {
        Method.post
        Path { 
            "someroute"
            Parse(.string)
            Parse(.string)
        }
        Body(.json(SomeModel.self))
    }
}

It throws me this compile error.

How can I solve this (theoretically shouldn't be) complicated task? I'm sure there's something I'm missing.
Thanks in advance.

[rcasula]

Anyone?

[mbrandonw]

Hi @rcasula, this is a bit of a gotcha with result builders, and hopefully it's something we can make a little bit nicer soon.

But the problem is that this kind of parser:

Path { 
  "someroute"
  Parse(.string)
  Parse(.string)
}
Body(.json(SomeModel.self))

…outputs a nested tuple of type ((String, String), SomeModel). The result builders can't automatically flatten that to (String, String, SomeModel).

The easiest fix is to define a type that holds both strings so you can parse into a single type:

Path { 
  Parse(.memberwise(SomeStrings.init)) {
    "someroute"
    Parse(.string)
    Parse(.string)
  }
}
Body(.json(SomeModel.self))

That will give you a tuple of (SomeStrings, SomeModel), and then that can be mapped into the enum case.

[rcasula]

It was simple and tricky at the same time, I guess I need to study more the parser's library. Thank you so much for your help!