Add producible field to product template and use it to select products to produce
It could be products that are not purchasable nor producible.
For example, products supplied by the customer to be manipulated (consumed in a production).
If we don't mark it as "purchasable", the stock_supply_production will plan a production for it [1] => WRONG
Of course, we can't mark it as "purchasable" (to avoid generate a production request) because "stock_supply" will generate a purchase request.
The solution is easy and match the criteria found in sale/purchase modules: the production module adds a "producible" boolean field in product template that is used:
- to show/hide the boms field in product.product
- add donain in production's product field to select only "producible" products (for coherence with sale/purchase modules, but it's not a requirement)
- in stock_supply_request, to generate production request only for products with this field True.
[1] http://hg.tryton.org/modules/stock_supply_production/file/79df65ef3bb6/production.py#l71