@as with "@react.component external" silently ignored in v12.0.0-beta.2 when some 3rdparty ppx is loaded

[reebalazs]

• Is it a bug? Usage questions should often be asked in the forum instead.
• Concise, focused, friendly issue title & description.
• A minimal, reproducible example.
• OS and browser versions, if relevant.
• Is it already fixed in master? Instructions

This happens in v12.0.0-beta.4. I noticed this when migrating my code from v11 to v12.

Minimal code as follows:

Define an external component with a parameter using @as:

  module Xxx = {
    @react.component
    external make: (@as("something") ~foo: string) => React.element = "myfunc"
  }

Then use it:

  <Xxx foo="bar" />

This compiles to the following with no error message:

          JsxRuntime.jsx(myfunc, {
            foo: "bar"
          }),

This compiled in v11 to the following. In my opinion this should be still the correct result. (I am not aware of @as being deprecated in external react components, but if so then an error would be appropriate)

          JsxRuntime.jsx(myfunc, {
            something: "bar"
          }),

[nojaf]

Hmm, this seems to work on the playground for me.
Is there something else of note about your code?

[reebalazs]

@nojaf, thanks, I suspected there might be something locally that affects it. I'll try to figure it out. Closing it for now.

[reebalazs]

@nojaf it looks like rescript-logger's ppx breaks it. I'll report it eventually against that package. EDIT: I can confirm with an empty project that adding rescript-logger's ppx breaks, but on my real project removing all rescript-logger still keeps it breaking. So the rabbit's hole is still deeper...

[reebalazs]

After further investigation, it appears that the ppx from both rescript-logger and rescript-embed-lang are independently causing the breakage.

Since neither of these packages has been updated for v12 yet, what do you think, @nojaf? Could this be a compiler issue anyhow that requires some attention here, or should I simply report the problem to both package maintainers and expect that updating their ppx will resolve it?

[nojaf]

There are some issues with ppx, like rescript-lang/rewatch#104

There might be two problems here:

• The ppx itself not longer works on the ReScript AST. There is mapper helper that should ensure things are compatible. This is something inside the compiler. Maybe there is a problem there.
• The ppx binary is not resolved, which is the issue mentioned in pnpm monorepo support - ppx resolution failing rewatch#104

When it comes to ppx, I don't really know much about them.
Is your real project a monorepo?

[reebalazs]

Yes, my actual project is a monorepo; however, I was also able to reproduce the problem in a minimal repository that is not a monorepo. So being a monorepo is not a prerequisite for this issue to appear.

Aside from the external @as silently being ignored, I haven’t encountered any other problems. Based on that, I’m inclined to think your first suggestion might indeed be the cause.

I’ll go ahead and report this to the package owners to see if they can address it.

[nojaf]

Could you share that sample? Would be interested to see it fail.

[zth]

It does sound like it could be an issue with the mapper. But I also think we recently did some work around attributes in this position. Would need to investigate.

[reebalazs]

Here is the repo: https://github.com/greenfinity/rescript-v12-external-as which tests it with rescript-logger/ppx.

I also made a branch with rescript-embed-lang/ppx (same case).

Thanks for taking a look!

[nojaf]

@reebalazs thanks for the repro.
So, I cloned this, yarn installed and ran npx rescript on main branch.
That worked for me. Does that fail for you? If so, which operation system are you on?

[reebalazs]

@nojaf I'm experiencing this issue on osx darwin-arm64. Although the compilation succeeds, the output in Rescript.bs.mjs is incorrect (as it's external, it would be hard to produce an example when the compilation breaks too):

import * as JsxRuntime from "react/jsx-runtime";

let Xxx = {};

JsxRuntime.jsx(myfunc, {
  foo: "bar"
});

export {
  Xxx,
}
/*  Not a pure module */

This should be

import * as JsxRuntime from "react/jsx-runtime";

let Xxx = {};

JsxRuntime.jsx(myfunc, {
  something: "bar"
});

export {
  Xxx,
}
/*  Not a pure module */

so basically the @as directive is silently ignored.

In contrast, the working branch, which excludes the ppx from rescript-logger (or rescript-embed-lang), compiles correctly for me.

[zth]

@nojaf I'm experiencing this issue on osx darwin-arm64. Although the compilation succeeds, the output in Rescript.bs.mjs is incorrect (as it's external, it would be hard to produce an example when the compilation breaks too):

import * as JsxRuntime from "react/jsx-runtime";

let Xxx = {};

JsxRuntime.jsx(myfunc, {
foo: "bar"
});

export {
Xxx,
}
/* Not a pure module */
This should be

import * as JsxRuntime from "react/jsx-runtime";

let Xxx = {};

JsxRuntime.jsx(myfunc, {
something: "bar"
});

export {
Xxx,
}
/* Not a pure module */
so basically the @as directive is silently ignored.

In contrast, the working branch, which excludes the ppx from rescript-logger (or rescript-embed-lang), compiles correctly for me.

Could you check if it works in any of the v12 versions? Would be good to understand roughly when it was reproduced.

[reebalazs]

@zth: 12.0.0-beta.1 working, 12.0.0-beta.2 broken

[zth]

@zth: 12.0.0-beta.1 working, 12.0.0-beta.2 broken

Perfect, thank you!