Separate default implementations from api.jl

[arnavk23]

• Create src/nlp/defaults.jl for default implementations
• Update src/NLPModels.jl to include defaults.jl after api.jl
• Move default implementations from api.jl to defaults.jl
• Replace implementations with function stubs in api.jl
• Resolves method overwriting warnings during precompilation

Functions refactored:

• grad(), cons(), cons!(), cons_lin(), cons_nln()
• jth_congrad(), objcons(), objcons!(), objgrad(), objgrad!()
• jac_structure(), jac_structure!(), jac_lin_structure(), jac_nln_structure()

Closes #385

[arnavk23]

@tmigot @amontoison please review this pr.

[tmigot]

Thanks @arnavk23 for the PR. Are you planning to do the same for NLS in a separate PR?

[dpo]

Functions refactored:

@arnavk23 Could you please explain what you refactored exactly?

[arnavk23]

Could you please explain what you refactored exactly?

@dpo

Files changed / added

• src/NLPModels.jl

  • Updated includes to load the new defaults files after API files:
    • Added include("nlp/defaults.jl")
    • Added include("nls/defaults.jl")
  • Reason: ensure API declarations are loaded first, then default implementations.

• src/nlp/api.jl

  • Replaced concrete method bodies with documentation + minimal stubs function foo end for many API entry points (keeps the docs while preventing duplicate definitions).

• src/nlp/defaults.jl (new)

  • Added the default implementations for NLP model APIs (the functions moved out of src/nlp/api.jl).
  • Purpose: provide fallback behavior for models that don’t implement specialized methods.

• src/nls/api.jl

  • Replaced concrete method bodies with stubs for the NLS API (preserved docs).

• src/nls/defaults.jl (new)

  • Added default implementations for NLS APIs (moved out of src/nls/api.jl).

Concrete functions moved (representative list)

NLP (moved into src/nlp/defaults.jl)

• Objective/constraint helpers: obj, obj!, objcons, objcons!, objgrad, objgrad!
• Gradients / constraints: grad, grad!, cons, cons!
• Jacobian helpers & structure: jac_structure, jac_structure!, jac_lin_structure, jac_nln_structure, jac_coord, jac, jac_lin_coord, jac_nln_coord
• Jacobian products: jprod, jprod_lin, jprod_nln, jtprod, jtprod_lin, jtprod_nln
• Operator forms: jac_op, jac_lin_op, jac_nln_op
• Hessian helpers: jth_hess_coord, jth_hess, jth_hprod, ghjvprod

NLS (moved into src/nls/defaults.jl)

• Residual & Jacobian: residual, residual!, jac_residual, jac_structure_residual, jac_structure_residual!, jac_coord_residual, jac_coord_residual!
• Jacobian products: jprod_residual, jprod_residual!, jtprod_residual, jtprod_residual!
• Jacobian operator: jac_op_residual, jac_op_residual!
• Hessian/residual Hessian helpers: hess_residual, hess_structure_residual, hess_structure_residual!, hess_coord_residual, hess_coord_residual!, jth_hess_residual_coord!, hprod_residual!, hess_op_residual!
• Objective/grad helpers adapted to NLS: obj, objcons!, grad!, objgrad!

Why this change fixes the problem

• Julia throws an error during precompilation when a method is defined more than once across files that are included during precompilation time.
• Moving implementations into defaults.jl and leaving api.jl as declarations prevents duplicate definitions (the API declares the name; the defaults file defines the fallback once).
• Including defaults after API files in src/NLPModels.jl ensures API declarations exist before default implementations are loaded.