fix: vue 3 checked state on GlFormCheckbox

Marina Mostirequested to merge
marina.mosti-3017-checkbox-checked-vue3 into main

What does this MR do?

Fixes an issue where GlFormCheckbox `checked` prop does not behave c... (#3017 - closed)

I've added the test that was an example in the issue, plus a story to check the use of a single checkbox without the v-model binding of the containing checkbox group.

Investigation

A couple of things were problematic.

1. domProps

domProps is no longer contained in a nested object for render functions, see https://v3-migration.vuejs.org/breaking-changes/render-function-api#vnode-props-format

⚠️ Update: I ended up reverting the change to flatten the domProps into the h object since its not technically needed for this issue, but it'll be good to keep this in mind when we remove compat.

2. v-model conflict

In Vue 3, v-model works by:

  • Automatically binding the value or modelValue prop to the element.
  • Emitting an update:modelValue event when the value changes.

Render Function Adjustment

Instead of using the legacy directives syntax, you directly bind the checked property (or other relevant props) and handle the change event manually, or you rely on v-model.

In Vue 3:

v-model uses the modelValue prop and update:modelValue event by default.

If you use checked directly, Vue binds it as a DOM property, ensuring it dynamically updates with the reactive value of isChecked. By removing the legacy model directive and switching to the native Vue 3 mechanism, the framework can properly track and sync reactivity.

Screenshots or screen recordings

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Edited by Marina Mosti

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