[Bridges] fix modify in Bridges.Objective.VectorSlack (#2144)

Author: odow

src/Bridges/Objective/bridges/vector_slack.jl

@@ -197,3 +197,11 @@ function MOI.get(
     g = MOI.Utilities.remove_variable(g, slacks)
     return MOI.Utilities.convert_approx(G, g)
 end
+
+function MOI.modify(
+    ::MOI.ModelLike,
+    ::VectorSlackBridge{T},
+    change::MOI.VectorConstantChange{T},
+) where {T}
+    return throw(MOI.ModifyObjectiveNotAllowed(change))
+end

test/Bridges/Objective/vector_slack.jl

@@ -148,6 +148,24 @@ function test_objective_function_value()
     return
 end
 
+function test_modify_vector_constant_change()
+    inner = MOI.Utilities.MockOptimizer(
+        MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Float64}()),
+    )
+    model = MOI.Bridges.Objective.VectorSlack{Float64}(inner)
+    x = MOI.add_variable(model)
+    f = MOI.Utilities.operate(vcat, Float64, -1.1 * x, 1.0 * x)
+    MOI.set(model, MOI.ObjectiveSense(), MOI.MAX_SENSE)
+    attr = MOI.ObjectiveFunction{typeof(f)}()
+    MOI.set(model, attr, f)
+    @test MOI.get(model, attr) ≈ f
+    @test_throws(
+        MOI.ModifyObjectiveNotAllowed,
+        MOI.modify(model, attr, MOI.VectorConstantChange([1.0, 2.0])),
+    )
+    return
+end
+
 end  # module
 
 TestObjectiveVectorSlack.runtests()