Add delete for nonlinear constraints (#3013)

src/nlp.jl

@@ -456,6 +456,18 @@ function is_valid(model::Model, c::NonlinearConstraintRef)
     return MOI.is_valid(model.nlp_model, index)
 end
 
+"""
+    delete(model::Model, c::NonlinearConstraintRef)
+
+Delete the nonlinear constraint `c` from `model`.
+"""
+function delete(model::Model, c::NonlinearConstraintRef)
+    _init_NLP(model)
+    index = MOI.Nonlinear.ConstraintIndex(c.index.value)
+    MOI.Nonlinear.delete(model.nlp_model, index)
+    return
+end
+
 """
     num_nonlinear_constraints(model::Model)
 

test/nlp.jl

@@ -1406,6 +1406,20 @@ function test_nonlinear_constraint_dual()
     return
 end
 
+function test_nonlinear_delete_constraint()
+    model = Model()
+    @variable(model, x)
+    @NLconstraint(model, c[i = 1:3], x^i <= i)
+    @test num_nonlinear_constraints(model) == 3
+    @test all_nonlinear_constraints(model) == [c[1], c[2], c[3]]
+    @test is_valid.(model, c) == [true, true, true]
+    delete(model, c[2])
+    @test num_nonlinear_constraints(model) == 2
+    @test all_nonlinear_constraints(model) == [c[1], c[3]]
+    @test is_valid.(model, c) == [true, false, true]
+    return
+end
+
 end
 
 TestNLP.runtests()