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commit: 6de73df

Original reported via https://github.com/Fattafatta/rescript-v12-test

@nojaf could this be involved?

        let element_binding =
          match config.module_ |> String.lowercase_ascii with
          | "react" -> Lident "ReactDOM"
          | _generic -> module_access_name config "Elements"
        in

This example also has the issue, without using a custom module:

@@config({
  flags: ["-bs-jsx", "4", "-bs-jsx-preserve"],
})

module React = {
  type component<'props> = Jsx.component<'props>
  type element = Jsx.element

  external jsx: (component<'props>, 'props) => element = "jsx"

  type fragmentProps = {children?: element}

  external jsxFragment: component<fragmentProps> = "Fragment"
}

let _fragment = <> {Jsx.string("Hello, world!")} </>

Cutting down further, this seems the problematic line. So somehow defining the jsx external makes preserve mode unhappy.

module React = {
  include React
  
  // This is the problematic line:
  external jsx: (component<'props>, 'props) => element = "jsx"
}

This with @module("react/jsx-runtime") makes it happy again.
There must be something in some transform or printing that relies on some details of the code generated when using @module in the external.

module React = {
  include React
  
  @module("react/jsx-runtime")
  external jsx: (component<'props>, 'props) => element = "jsx"
}

This with @module("react/jsx-runtime") makes it happy again. There must be something in some transform or printing that relies on some details of the code generated when using @module in the external.

module React = {
  include React
  
  @module("react/jsx-runtime")
  external jsx: (component<'props>, 'props) => element = "jsx"
}

Indeed the generated lambda is slightly different in the identifier used (where dump recognises "jsx"). Fixed in #7591