code: function productVariationUpdated( state, action ) {
  	const { data: productVariation, productId } = action;
  	const productVariations = state.productVariations || [];
  	const index = findIndex( productVariations, { id: productVariation.id } );
  
  	const newProductVariation = { ...productVariation, productId };
  	const newProductVariations = [ ...productVariations ];
  
  	if ( -1 < index ) {
  		newProductVariations[ index ] = newProductVariation;
  	} else {
  		newProductVariations.push( newProductVariation );
  	}
  
  	const promotions = calculatePromotions( state.coupons, state.products, newProductVariations );
  
  	return { ...state, productVariations: newProductVariations, promotions };
  }
docs: TODO: Update this for performance if needed. As-is, it will cause frequent recalculations.