Heat the oven to 350°F and coat a 9-by-13-inch baking dish with cooking spray.
Spread the cherry pie filling across the bottom of the dish and sprinkle the dry cake mix evenly over it.
Pour the hot water slowly over the entire surface, then drizzle on the melted butter without stirring.
Scatter the chocolate chips across the damp top.
Bake uncovered for 38 to 42 minutes, until the cake layer is set at the center but glossy chocolate-cherry sauce still bubbles around the edges.
Rest for 20 minutes and serve with the pudding-like sauce from the bottom.