Set ToastrOptions as variable

[XF9]

Hi,

we are currently in the progress of migrating from webpack to vite. We noticed an error popping up when starting vite as a dev server, complaining that it can't set Toast_options because it's a constant:

  ✘ [ERROR] Cannot assign to "Toastr_options" because it is a constant

    fable_modules/Elmish.Toastr.2.1.0/Elmish.Toastr.fs.js:162:4:
      162 │     Toastr_options = (Object.assign({}, Toastr_options, opts));
          ╵     ~~~~~~~~~~~~~~

  The symbol "Toastr_options" was declared a constant here:

    fable_modules/Elmish.Toastr.2.1.0/Elmish.Toastr.fs.js:156:13:
      156 │ export const Toastr_options = options_1;
          ╵              ~~~~~~~~~~~~~~

I created a minimal example here: https://github.com/rheinspree/vite-toastr

Just run npm install, dotnet fable and npx vite serve and it will show the error.

---

The culprit seems to be this line let mutable private options : ToastrOptions = import "options" "toastr". Despite being mutable the import statement creates a constant when being compiled by fable: export const Toastr_options = options_1 (https://fable.io/docs/javascript/features.html#import-1)

My solution would be to assign the import to optionsImport and assign that to the original options. This creates the following JavaScript:

export const Toastr_optionsImport = options_1;
let Toastr_options = Toastr_optionsImport;

I'm not deep into fable nor toastr so I'm not sure if that's a viable solution or if there are any undesired side effects.

---

The error never occurred with webpack nor vite build, probably due to tree shaking.

[tforkmann]

@Zaid-Ajaj We are running into the same issue. Any chance this can be merged and released?