To be technical Avignon was not then part of France. It was part of the Kingdom of Burgundy or Arles in the Holy Roman Empire, or would be except that the Pope claimed to be an independent monarch.
The kingdom of Arles included about one sixth of modern france. By 1789 the King of France and the Swiss Confederation had acquired most of the counties and duchies and other lands in the kingdom. But in some of those lands the King of France still used in official documents a title in the form of "King of France and Count of Provence", for example, instead of plain "King of France and Navarre" as in France itself, and thus acknowledged that those lordships were outside of France.