Keep order of selection if multiple items were selected in `input_selectize`

[DvGils]

Hi!

I noticed Shiny will not keep the order of items that you set in the selected argument. For my use case this ordering matters. The following code will set the order to "A", "C", "D" instead of "C", "A", "D"

from shiny import App, ui, render, reactive

app_ui = ui.page_fluid(
    ui.h3("Order of Selected Items in ui.input_selectize()"),
    ui.input_selectize(
        "my_selectize",
        "Choose items:",
        choices=["A", "B", "C", "D"],
        selected=["C", "A", "D"],
        multiple=True,
    ),
)


def server(input, output, session): ...


app = App(app_ui, server)

Pretty sure the issue lies in:

#_input_selectize.py
def _render_choices(
    x: _SelectChoices, selected: Optional[str | list[str]] = None
) -> TagList:
    result = TagList()

    if x is None:
        return result

    for k, v in x.items():
        if isinstance(v, Mapping):
            result.append(
                tags.optgroup(
                    *(_render_choices(cast(_SelectChoices, v), selected)), label=k
                )
            )
        else:
            is_selected = False
            if isinstance(selected, list):
                is_selected = k in selected
            else:
                is_selected = k == selected

            result.append(tags.option(v, value=k, selected=is_selected))

    return result

Is there a chance this can be fixed?

An additional note; it is strange to me that input.my_selectize() will return a tuple, but the selected will not accept a tuple, only a list.

[cpsievert]

FWIW, there is a workaround for this -- first, avoid selected when creating the input:

ui.input_selectize(
    "z",
    "Choose items:",
    choices=["A", "B", "C", "D"],
    multiple=True,
)

Then, when the session starts, update the selected values

@reactive.effect
def _():
    ui.update_selectize(
        "z",
        selected=["C", "A", "D"],
    )

@elnelson575 since this workaround exists, I think it's OK if we punt on this (at least for now)