Like @aenglisc said, there’s a confusing mix of stream and assign for list of products. It should usually be one or the other for any particular data structure.
The simplest approach to get the book code working would likely be switching the use of stream in the mount callback to assign i.e. {:ok, assign(socket, :products, Catalog.list_products()}. All of the book code’s view templates are referencing the products in the top level of the socket assigns and not the products nested under the streams key in the socket assigns.
If you really want to use the new streaming functionality, you’ll have to update the book code to re-stream_insert all the individual products within the :products stream since there’s no API to replace an entire stream at the collection level – at least for now. For more details, see: How to replace LiveView stream with new items? (reset or re-assigning) - #2 by codeanpeace
