🐛 Fix NodeChangeProperty not including the 'variant' key

[Lorenzo-Tr]

Add 'variant' to NodeChangeProperty

Problem

The NodeChangeProperty union type is missing 'variant' as a valid value. However, at runtime, when a variant changes on an InstanceNode, the documentchange event does return 'variant' inside the properties array:

{
  "type": "PROPERTY_CHANGE",
  "properties": ["variant"]
}

This means plugin developers cannot check for variant changes in a type-safe way. The only workaround is an unsafe cast:

(change.properties as (NodeChangeProperty | 'variant')[]).includes('variant')

Fix

Added 'variant' to the NodeChangeProperty union type so that variant changes on InstanceNode can be detected without bypassing TypeScript's type system.

Testing

You can verify the fix by listening to document changes and swapping the variant of an InstanceNode in the canvas:

figma.on('documentchange', (event) => {
  for (const change of event.documentChanges) {
    if (
      change.type === 'PROPERTY_CHANGE' &&
      change.properties.includes('variant') // ✅ now valid without casting
    ) {
      console.log('Variant changed on node:', change.node.id)
    }
  }
})

[Lorenzo-Tr]

@rmah-figma Hello, I ping you to know if it could be merge or not ?