Optional parameters with defined type not wrapping it with option variant.

[kd4001]

I have 3 scenarios where a function take optional parameters.

let getModifiedTitle = (~title: someVariant=?) => {
    blah blah blah...
}

let getModifiedTitle = (~title=?) => {
    blah blah blah...
}

let getModifiedTitle = (~title: option(someVariant)=?) => {
    blah blah blah...
}

So in 1st scenario it doesn't wrap the title param with option where as in 2nd scenario it does. So to wrap it with option variant I have to explicitly wrap it.

Now the problem is none of the scenario gives error.
Where as 1st scenario should give an error.

For example,

Let's say I have below scenario.

type someVariant = 
    | Text(string)
    | Custom(unit => React.element);

let getModifiedTitle = (~title: someVariant=?) => {
    switch(title) {
       | Text(title) => <div>{React.string(title)}</div>
       | Custom(fn) => fn()
    }
}

Now if I call the function getModifiedTitle() and don't pass title, it won't throw error on compile time. Rather it would break in run time.

I think it should either wrap it with option variant and therefore it should ask to wrap it with option switch case or just raise an error on compile time.

The 2nd scenario handles this but the 1st scenario should throw an error.

For reproducing the issue
Please clone this repo - https://github.com/ka-ran/reason-react-boilerplate/tree/example
Checkout to example branch
Follow Readme.md .
Run the code.
Hope this helps

Desc- There are two components. Component1 and Component2. The code breaks in case of component2.

[gaku-sei]

It seems to be a known issue with the react.component ppx actually: reasonml/reason-react#451

This code alone:

let f = (~x: t=?) => ();

Would not compile (outside the react.component ppx, and provided the type t is not an alias for an option). Playground.

Unfortunately there is no updates regarding this issue (and others).

[bobzhang]

moved reasonml/reason#2535

[ryyppy]

@bobzhang as @gaku-sei said, this issue is most likely caused by the reactjs_jsx_ppx.cppo.ml located in bucklescript.

Looking through the code, I feel like the error is somewhere located here?

\cc @rickyvetter

[rickyvetter]

Are you using a version of BuckleScript which relies on OCaml 4.02? The 4.02 version of the AST doesn’t allow us to check this properly (as far as I can tell). This shouldn’t happen in the PPX for 4.06 versions of OCaml.

[ryyppy]

@rickyvetter the example project by @gaku-sei reproducing the problem is running on bs-platform@7.0.1 (running on OCaml 4.06).

To get to the gist of the problem, here is the Component2.re snippet from the repo:

type title =
  | Text(string)
  | Custom(unit => React.element);

let getTitle = (~title: title) => {
  switch title {
  | Text(title) => <div>{React.string(title)}</div>
  | Custom(fn) => fn()
  };
};

[@react.component]
let make = (~title: title=?) => {
  <div>
    {getTitle(~title)}
  </div>
};

This snippet should not compile, since ~title is an optional label, therefore it should be of type option(title). As soon as you attach the [@react.component] annotation, the compiler will compile the snippet gracefully and a potential runtime error is introduced.

I don't think this is desired behavior?