SimpleTextarea does not show placeHolder

[xmedeko]

I have SimpleTextarea with placeHolder:

<textarea data-dojo-type="dijit/form/SimpleTextarea" data-dojo-props="placeHolder:'Text area placeholder'></textarea>

but the placeHolder is not shown, because although SimpleTextarea descents from TextBox, it changes templateString and the placeHolder has nowhere to attach in

dijit/form/TextBox.js

Lines 68 to 73 in 8ab4cdc

	this._phspan = domConstruct.create('span', {
	// dijitInputField class gives placeHolder same padding as the input field
	// parent node already has dijitInputField class but it doesn't affect this <span>
	// since it's position: absolute.
	className: 'dijitPlaceHolder dijitInputField'
	}, this.textbox, 'after');

(because this.textbox has no parentElement).