Public guidance for solver wrappers converting maxiters

[mmikhasenko]

Downstream solver wrappers may want to translate the common maxiters keyword into a backend-specific call limit.

Minuit2.jl previously used the internal helper Optimization._check_and_convert_maxiters(maxiters). With Optimization 5.2.0 this helper is no longer defined, so downstream code that relied on it fails before reaching the solver.

Compact reproduction:

julia> using Optimization

julia> pkgversion(Optimization)
v"5.2.0"

julia> isdefined(Optimization, :_check_and_convert_maxiters)
false

julia> Optimization._check_and_convert_maxiters(nothing)
ERROR: UndefVarError: `_check_and_convert_maxiters` not defined in `Optimization`

In Minuit2.jl this caused the Optimization extension to fail during solve(...) before calling Minuit. We can avoid the breakage locally by converting nothing/non-negative numeric maxiters to the backend's ncall keyword ourselves, but it would be helpful to know whether Optimization.jl intends solver wrappers to:

• implement this conversion locally;
• use a public replacement helper; or
• avoid this conversion entirely and pass raw common keywords through another API.

If there is a preferred public API for this in Optimization 5.x, a pointer would be enough.

[SebastianM-C]

You need to use OptimizationBase._check_and_convert_maxiters, Optimzation v5 moved the API surface to OptimizationBase and the main Optimization.jl is mostly an umbrella package now.

For your extension code you would only need to depend on OptimizationBase and not on Optimization, which is also a lighter dependency.