selected should be a boolean attribute

[fviolette]

Astro Info

Astro                    v5.0.0-beta.1
Node                     v22.8.0
System                   macOS (arm64)
Package Manager          npm
Output                   static
Adapter                  none
Integrations             auto-import
                         @astrojs/sitemap
                         @astrojs/preact
                         @astrojs/asides
                         astro-expressive-code
                         @astrojs/pagefind
                         @astrojs/mdx

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

No response

Describe the Bug

When dynamically adding the selected attribute on <option>, Astro preserves the full attribute with its value: selected="true" or selected="false".

On v4.X, selected="true" was output when true and nothing was, when false.

I notice that selected is not part of the list of boolean attributes at: https://github.com/withastro/astro/blob/astro%405.0.0-beta.1/packages/astro/src/runtime/server/render/util.ts#L9

What's the expected result?

As per https://5-0-0-beta.docs.astro.build/en/guides/upgrade-to/v5/#changed-non-boolean-html-attribute-values, I expect the output of selected={true} should be selected, selected={false} should not output anything.

Link to Minimal Reproducible Example

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

Participation

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

[bluwy]

Good catch! Looks like an easy fix. I think editing the regex without tests should be fine if you'd like to contribute.

[fviolette]

Here's my attempt at #12027.