client/extensions/woocommerce/state/sites/products/reducer.js
function setLoading( state, params, newStatus ) {
	const queries = ( state.queries && { ...state.queries } ) || {};
	const key = getSerializedProductsQuery( params );
	queries[ key ] = { ...( queries[ key ] || {} ), isLoading: newStatus };
	return queries;
}
function setLoading( state, params, newStatus ) {
	const queries = ( state.queries && { ...state.queries } ) || {};
	const key = getSerializedProductsQuery( params );
	queries[ key ] = { ...( queries[ key ] || {} ), isLoading: newStatus };
	return queries;
}
Set the loading status for a param set in state

@param  {Object}  state     The current state
@param  {Object}  params    Params of the query to update
@param  {Boolean} newStatus The new value to save
@return {Object}            Updated isLoading state