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plugin/bound: reapply the select value when its options change #77

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Merged
rameel merged 1 commit into from
Oct 25, 2026
Merged

plugin/bound: reapply the select value when its options change #77

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25 changes: 15 additions & 10 deletions src/plugins/bound/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -170,24 +170,29 @@ function plugin({ directive, entangle, evaluateLater, mapAttributes, mutateDom,
break;

case "SELECT":
// WORKAROUND:
// For the "select" element, there might be a situation
// where options are generated dynamically using the "x-for" directive,
// and in this case, attempting to set the "value" property
// will have no effect since there are no options yet.
// Therefore, we use a small trick to set the value a bit later
// when the "x-for" directive has finished its work.
// Alpine initializes the options after this directive runs:
// "x-for" renders them and ":value" binds their values.
// The value read from the element before that would be wrong,
// so the binding starts a bit later.
const timer_id = setTimeout(() => {
const apply = () => apply_select_values(el, as_array(get_value() ?? []));

// if the value of the bound property is "null" or "undefined",
// we initialize it with the value from the element.
is_nullish(get_value()) && update_variable();

effect(() => apply_select_values(el, as_array(get_value() ?? [])));
effect(apply);
cleanup(listen(el, "change", () => set_value(collect_selected_values(el))));

// the options and their values can change later, e.g. when
// the "x-for" items do, so the selection is applied again
const observer = new MutationObserver(apply);
observer.observe(el, { childList: true, subtree: true, characterData: true, attributeFilter: ["value"] });
cleanup(() => observer.disconnect());
});

// the element can be destroyed before the timer fires,
// and the effect and listener created after that would never be released.
// the element can be destroyed before the timer fires, and the effect,
// listener and observer created after that would never be released.
cleanup(() => clearTimeout(timer_id));

processed = true;
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66 changes: 66 additions & 0 deletions tests/playwright/x-bound.spec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -331,6 +331,72 @@ test.describe("x-bound: select", () => {
await expect(page.locator("span")).toHaveText("1");
});

test("select (options rendered later)", async ({ page }) => {
await set_html(page, `
<div x-data="{ value: '2', options: [] }">
<select &value>
<template x-for="v in options" :key="v">
<option :value="v" x-text="v"></option>
</template>
</select>
</div>`);

const root = page.locator("div");

await set_data(root, { options: ["1", "2", "3"] });
await expect(page.locator("select")).toHaveValue("2");

// Without its option the select shows the first one,
// while the property keeps its value until the option is back
await set_data(root, { options: ["1", "3"] });
await expect(page.locator("select")).toHaveValue("1");

await set_data(root, { options: ["1", "2", "3"] });
await expect(page.locator("select")).toHaveValue("2");
expect(await root.evaluate(el => Alpine.$data(el).value)).toBe("2");
});

test("select (option values change)", async ({ page }) => {
await set_html(page, `
<div x-data="{ value: '2', options: [{ id: '1' }, { id: '2' }] }">
<select &value>
<template x-for="option in options">
<option :value="option.id" x-text="option.id"></option>
</template>
</select>
</div>`);

await expect(page.locator("select")).toHaveValue("2");

// The selected option gets the value "1", and the first option
// gets the value "2", which becomes selected instead
await page.locator("div").evaluate(async el => {
const { options } = Alpine.$data(el);
[options[0].id, options[1].id] = ["2", "1"];
await Alpine.nextTick();
});

await expect(page.locator("select")).toHaveValue("2");
});

test("select multiple (options rendered later)", async ({ page }) => {
await set_html(page, `
<div x-data="{ value: ['2', '3'], options: ['1', '2'] }">
<select &value multiple>
<optgroup label="Options">
<template x-for="v in options" :key="v">
<option :value="v" x-text="v"></option>
</template>
</optgroup>
</select>
</div>`);

await expect(page.locator("select")).toHaveValues(["2"]);

await set_data(page.locator("div"), { options: ["1", "2", "3"] });
await expect(page.locator("select")).toHaveValues(["2", "3"]);
});

test("initialize from element when property is null", async ({ page }) => {
await set_html(page, `
<div x-data="{ value: null }">
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