Discussion: Should `MOI.set` perform complex operations?

[joaquimg]

As far as I understand MOI.set is primarily used for setting attributes.

However, #356 introduced:
function MOI.set(model::Model, ::DiffOpt.ForwardDifferentiate)
as a replacement to
function forward_differentiate!(model)

Historically, performing more complex operations has been left (mostly?) for special functions such as:

• compute_conflict!
• write_to_file
• read_from_file
• submit
• transform

A partial counter argument is:

• Utilities.PenaltyRelaxation, but it is a modify not even a set
  I do think modify here makes sense.

Are there any other arguments to each side? any other precedent?

I would like to have the reasoning for that clarified.

What are de advantages and disadvantages?

Bonus:
As a follow-up, we should have good practices and standards documented to help developers consistently make decisions in these cases.

[joaquimg]

cc @blegat @odow

[odow]

• transform: this seemed a good idea at the time. I don't think anyone actually uses it.
• read/write to file: seemed reasonable. Still is.
• compute_conflict: terrible. What a bad name. I wonder if it could just have been activated on the first get of ConflictStatus or something.
• submit: there's such a minor difference between submit and set. We probably could have used set, even if the verb is a bit weird
• PenaltyRelaxation: since it modifies the model in-place, great.

Overall, I'm in favour of more attributes and fewer functions.

The set is okay for me. Perhaps MOI.set(model, DiffOpt.ForwardDerivatives()) reads better?