Add missing cubic parametric function type handling (#225)

* Add missing cubic parametric cubic type

* format

Author: joaquimg

src/MOI_wrapper.jl

@@ -1664,7 +1664,9 @@ queried using the [`ParametricObjectiveFunction{P}`](@ref) attribute. The type
 struct ParametricObjectiveType <: MOI.AbstractModelAttribute end
 
 function MOI.get(model::Optimizer{T}, ::ParametricObjectiveType) where {T}
-    if model.quadratic_objective_cache !== nothing
+    if model.cubic_objective_cache !== nothing
+        return ParametricCubicFunction{T}
+    elseif model.quadratic_objective_cache !== nothing
         return ParametricQuadraticFunction{T}
     elseif model.affine_objective_cache !== nothing
         return ParametricAffineFunction{T}
@@ -1704,6 +1706,18 @@ function MOI.get(
     return model.affine_objective_cache
 end
 
+function MOI.get(
+    model::Optimizer{T},
+    ::ParametricObjectiveFunction{ParametricCubicFunction{T}},
+) where {T}
+    if model.cubic_objective_cache === nothing
+        error("
+            There is no parametric cubic objective function in the model.
+        ")
+    end
+    return model.cubic_objective_cache
+end
+
 """
     ListOfParametricConstraintTypesPresent()
 

test/test_cubic.jl

@@ -1623,6 +1623,40 @@ function test_jump_cubic_direct_model_ppp()
     return
 end
 
+function test_parametric_objective_type_cubic()
+    model = Model(() -> POI.Optimizer(HiGHS.Optimizer()))
+    set_silent(model)
+    @variable(model, x)
+    @variable(model, p in MOI.Parameter(2.0))
+    @variable(model, q in MOI.Parameter(3.0))
+    @constraint(model, x >= 1)
+    @objective(model, Min, x + p * q^2)
+    optimize!(model)
+    inner = unsafe_backend(model)
+    @test MOI.get(inner, POI.ParametricObjectiveType()) ==
+          POI.ParametricCubicFunction{Float64}
+    pf = MOI.get(
+        inner,
+        POI.ParametricObjectiveFunction{POI.ParametricCubicFunction{Float64}}(),
+    )
+    @test pf isa POI.ParametricCubicFunction{Float64}
+    return
+end
+
+function test_parametric_objective_type_cubic_error()
+    model = Model(() -> POI.Optimizer(HiGHS.Optimizer()))
+    set_silent(model)
+    @variable(model, x >= 1)
+    @objective(model, Min, x)
+    optimize!(model)
+    inner = unsafe_backend(model)
+    @test_throws ErrorException MOI.get(
+        inner,
+        POI.ParametricObjectiveFunction{POI.ParametricCubicFunction{Float64}}(),
+    )
+    return
+end
+
 end  # module
 
 TestCubic.runtests()