Cost allocation for Production

Production costs are wrongly calculated. It is a case when the FIFO cost method
is used for input products. It takes the cost of product instead of values of
actual stock moves used in production.

added type::behavior + 1 deleted label

After production is "run", the cost price becomes correct, but it is not
transferred to production.outputs cost.
This results to the exception when trying to "done" the production: Production
"x" misses costs on some of its outputs.

added 1 deleted label and removed 1 deleted label

So I see nothing wrong here, you just would like to have a new feature:
automatic allocation of the cost.

For me it looks like more a bug than a feature. The user manually needs to
adjust outputs costs of *every* production with FIFO input(s).

And how should the cost being allocated?

The same method like in Production.explode_bom, just only using input.cost_price
instead of input.product.cost_price.

In addition, the cost allocation could be splitted out from
Production.explode_bom into the new method and re-used twice. First time - in
(or after) Production.explode_bom, second - in Production.run()

I see your point now. Yes, allocation for multiple outputs is not possible. I
was talking only about the production with a single output.

I agree, it is an additional feature.

To implement a simple allocation, I suggest to add these fields to BOM.output:

* Allocation type: Selection(['fixed', 'multiplier'])
* Cost price: Decimal, visible when type == 'fixed'
* Multiplier: Float, visible when type == 'multiplier'

Then for allocation type == 'multiplier', production.output.cost_price =
(production.cost - all_fixed) * ratio / BOM.output.quantity
Where all_fixed = sum(for all fixed outputs)
And ratio = BOM.output.multiplier / sum(for all BOM output multipliers)

assigned to @ced

added 1 deleted label and removed 1 deleted label

I propose to add on the bom outputs a distribution factor of the cost.
So the production will be able to distribute the cost automatically.
This will allow to apply the same design as #8795 (closed) to recompute the production cost after the production is done (with user intervention).

I forgot the case if there is no BOM on the production.
Indeed there are standardized methods [1] to allocate cost to by-product.
So the new proposal is to allocate the cost based on the list price of each products (and ignore products without list price).

[1] https://www.accountingtools.com/articles/2017/5/14/by-product-costing-and-joint-product-costing

Here is review288471002 which always allocates the cost of production in such way that we can remove the constraint.

added 1 deleted label and removed 1 deleted label

review288471002 updated at https://codereview.tryton.org/288471002/#ps276291002

review288471002 updated at https://codereview.tryton.org/288471002/#ps254591002

review288471002 updated at https://codereview.tryton.org/288471002/#ps288461007

New changeset 0b2e50445415 by Cédric Krier in branch 'default':
Allocate cost based on list price of each product
https://hg.tryton.org/modules/production/rev/0b2e50445415

closed