What exactly does Buttons' "has-icon" do?

[datvm]

Is it like another component where it's for SSR only? Icon is shown or not currently depend on the icon slot being given:

• hasIcon = false, no slot="icon":
  

• hasIcon = false, there is slot="icon":
  

• hasIcon = true, no slot="icon":
  

• hasIcon = true, there is slot="icon":
  

Is this property really needed? Can't it be deducted from @queryAssignedElements({slot: 'icon', flatten: true})?

[asyncLiz]

Is it like another component where it's for SSR only?

Yes! Due to limitations with slotchange logic in SSR.

These attributes are only needed to avoid a Flash Of Unstyled Content (FOUC). For the button, that means the icon popping in and changing the width when the page's javascript loads.