Expose method to get current active style

[simison]

Is your feature request related to a problem? Please describe.

Consider plugin author wanting to show or disable different block sidebar settings depending on active style.

wp-editor's blockStyles component has getActiveStyle method but it isn't exposed to be used outside the package:

gutenberg/packages/editor/src/components/block-styles/index.js

Lines 22 to 44 in cb809b9

	/**
	* Returns the active style from the given className.
	*
	* @param {Array} styles Block style variations.
	* @param {string} className Class name
	*
	* @return {Object?} The active style.
	*/
	export function getActiveStyle( styles, className ) {
	for ( const style of new TokenList( className ).values() ) {
	if ( style.indexOf( 'is-style-' ) === -1 ) {
	continue;
	}
	const potentialStyleName = style.substring( 9 );
	const activeStyle = find( styles, { name: potentialStyleName } );
	if ( activeStyle ) {
	return activeStyle;
	}
	}
	return find( styles, 'isDefault' );
	}

Describe the solution you'd like
Please export utils to modify styles; get lists, get active state, change styles so that plugin authors can build more complex sidebar settings around these features.

Describe alternatives you've considered
It's obviously already possible to use these methods by just copying them directly to block code. Boo code duplication.

[youknowriad]

I agree this should be done, I think we could expose the active style directly in a special prop in the edit/save functions. I think there might be an existing issue about this?

[simison]

I like that even better. :-)

I'm trying to imagine if there are a situations where plugin author would want to use a setter method?

Perhaps activate different style by default when inserting the block, perhaps by picking the style from previously inserted child block inside the parent block? Or hide some styles by changing some setting at the sidebar?

[youknowriad]

Actually, this is a duplicate of #13506, so let's discuss there instead.