@atlaskit/pragmatic-drag-and-drop-react-beautiful-dnd-migration/dist/es2019/drag-drop-context/get-destination.js

An optional Pragmatic drag and drop package that enables rapid migration from react-beautiful-dnd to Pragmatic drag and drop

// eslint-disable-next-line import/no-extraneous-dependencies

/**
 * Calculates the actual destination of an item based on its start location
 * and target location.
 *
 * The actual destination may not be the same as the target location.
 * An item moving to a higher index in the same list introduces an
 * off-by-one error that this function accounts for.
 */
export function getActualDestination({
  start,
  target
}) {
  if (target === null) {
    return null;
  }

  /**
   * When reordering an item to an index greater than its current index
   * in the same list, then the target index needs adjustment.
   *
   * This is to account for the item itself moving, which would cause a shift.
   */
  const isSameList = start.droppableId === target.droppableId;
  const isMovingForward = target.index > start.index;
  const shouldAdjust = isSameList && isMovingForward;

  /**
   * A clone is returned, even though it is the same value.
   * This is because the returned object might be mutated.
   */
  if (!shouldAdjust) {
    return {
      ...target
    };
  }
  return {
    ...target,
    index: target.index - 1
  };
}