Using 'selected' attribute with Lit components in Astro breaks after PR #12027

[Masty88]

Astro Info

Astro                    v5.2.5
Node                     v20.11.1
System                   Windows (x64)
Package Manager          npm
Output                   static
Adapter                  @astrojs/vercel
Integrations             @astrojs/lit
                         astro-d2-integration
                         @astrojs/starlight

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

Following PR #12027 (which added selected to Astro's list of boolean attributes), using the selected attribute to pass non-boolean values to Lit components in Astro is now broken, as selected is treated as a boolean attribute.

After PR #12027 was merged, the selected attribute was added to Astro's boolean attributes list. This means that in Astro templates, selected is now treated strictly as a boolean attribute rather than allowing string or other values.

This creates compatibility issues when using Lit components that expect non-boolean values through a selected attribute, such as:

<!-- This no longer works as expected -->
<my-lit-component selected="some-value"></my-lit-component>

The component receives the selected attribute as a boolean rather than the string value, causing type errors and broken functionality.

Affected Components

Any Lit components using selected attribute for non-boolean values
Custom elements that expect string/object values through selected attribute

What's the expected result?

the selected attribute should be treated as a string/object value but instead it's now being treated as a boolean attribute by Astro. This means:
Expected behavior:

<color-picker selected="blue">
<!-- should receive "blue" as a string value -->

Actual behavior:

<color-picker selected="blue">
<!-- receives true as a boolean value -->

This breaks any component logic that expects to receive string values through the selected attribute.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/withastro-astro-qib1knph?file=src%2Fpages%2Findex.astro

Participation

• I am willing to submit a pull request for this issue.