Duplicate generated classNames when using useBlockProps.save()

[fabiankaegy]

Describe the bug
When using the useBlockProps.save() function like this:

save: () => {
    return (
        <div {...useBlockProps.save()}>
            Example Block New
        </div>
    )
}

with color in the block supports I get all the auto generated classNames output twice:

<div class="wp-block-example-example-new alignwide has-background has-background" style="background-color:#a26a79">Example Block New</div>

To reproduce
You can replicate it with this Block setup:

import { registerBlockType } from '@wordpress/blocks';
import { useBlockProps } from '@wordpress/block-editor';
import { __ } from '@wordpress/i18n';

const NAMESPACE = 'example';

registerBlockType( `${ NAMESPACE }/example-new`, {
    title: __( 'Example Block (New)', NAMESPACE ),
    description: __( 'Example Block', NAMESPACE ),
    icon: 'smiley',
    category: 'common',
    example: {},
    supports: {
        html: false,
        lightBlockWrapper: true,
        align: true,
        anchor: true,
        color: {
            link: true
        },
    },
    attributes: {},
    transforms: {},
    variations: [],
    edit: () => {
        return (
            <div {...useBlockProps()}>
                <p>Hello World</p>
            </div>
        )
    },
    save: () => {
        return (
            <div {...useBlockProps.save()}>
                Example Block New
            </div>
        )
    }
} );

Expected behavior
The classes should only be generated once.

Editor version (please complete the following information):

• WordPress version: 5.5.3
• Does the website has Gutenberg plugin installed, or is it using the block editor that comes by default? [ gutenberg plugin ]
• If the Gutenberg plugin is installed, which version is it? 9.2.2

[talldan]

I could reproduce using both lightBlockWrapper and the newer apiVersion: 2.

[talldan]

Seems I made a mistake in my previous testing, apiVersion: 2 doesn't have this issue.

#27189 should fix the issue for blocks still using lightBlockWrapper.