[Bridges] fix deleting variable in Bridges.Variable.VectorizeBridge (#2393)

Author: odow

src/Bridges/Variable/bridges/vectorize.jl

@@ -98,10 +98,14 @@ function MOI.get(
     return [bridge.vector_constraint]
 end
 
-# References
 function MOI.delete(model::MOI.ModelLike, bridge::VectorizeBridge)
-    MOI.delete(model, bridge.variable)
-    return
+    # It isn't safe to delete the variable because the constant may appear in
+    # other parts of the model (like the objective, or right-hand side sets).
+    err = MOI.DeleteNotAllowed(
+        bridge.variable,
+        "Cannot delete variable because it is bridged by the `VectorizeBridge`.",
+    )
+    return throw(err)
 end
 
 # Attributes, Bridge acting as a constraint

test/Bridges/Variable/vectorize.jl

@@ -233,14 +233,14 @@ function test_exp3_with_add_constrained_variable_y()
     MOI.set(bridged_mock, MOI.VariablePrimalStart(), y, 1.0)
     @test MOI.get(mock, MOI.VariablePrimalStart(), z) == -4
     @test MOI.get(bridged_mock, MOI.VariablePrimalStart(), y) == 1
+    return
+end
 
-    _test_delete_bridged_variable(
-        bridged_mock,
-        y,
-        MOI.LessThan{Float64},
-        2,
-        ((MOI.VectorOfVariables, MOI.Nonpositives, 0),),
-    )
+function test_delete_variable()
+    inner = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Float64}())
+    model = MOI.Bridges.Variable.Vectorize{Float64}(inner)
+    x, _ = MOI.add_constrained_variable(model, MOI.GreaterThan(1.0))
+    @test_throws MOI.DeleteNotAllowed{MOI.VariableIndex} MOI.delete(model, x)
     return
 end
 

test/Bridges/lazy_bridge_optimizer.jl

@@ -519,17 +519,6 @@ function _test_SDPA_format(T)
     @test MOI.Bridges.bridge_type(bridged, MOI.RotatedSecondOrderCone) ==
           MOI.Bridges.Variable.RSOCtoPSDBridge{T}
     x, cx = MOI.add_constrained_variable(bridged, MOI.LessThan(one(T)))
-    _test_delete_bridged_variable(
-        bridged,
-        x,
-        MOI.LessThan{T},
-        1,
-        (
-            (MOI.VectorOfVariables, MOI.Nonnegatives, 0),
-            (MOI.VectorOfVariables, MOI.Nonpositives, 0),
-        ),
-        used_bridges = 2,
-    )
     @test !MOI.supports_constraint(
         bridged,
         MOI.VectorAffineFunction{T},