[Bridges] change supports for AbstractConstraintAttribute to OR formulation

src/Bridges/bridge_optimizer.jl

@@ -1442,49 +1442,28 @@ function MOI.supports(
     #     This function is slightly confusing, because we need to account for
     #     the different ways in which a constraint might be added.
     if F == MOI.Utilities.variable_function_type(S)
-        # These are VariableIndex and VectorOfVariable constraints.
-        if is_bridged(b, S)
-            # If S needs to be bridged, it usually means that either there is a
-            # variable bridge, or that there is a free variable followed by a
-            # constraint bridge (i.e., the two cases handled below).
-            #
-            # However, it might be the case, like the tests in
-            # Variable/flip_sign.jl, that the model supports F-in-S constraints,
-            # but force-bridges S sets. If so, we might be in the unusual
-            # situation where we support the attribute if the index was added
-            # via add_constraint, but not if it was added via
-            # add_constrained_variable. Because MOI lacks the ability to tell
-            # which happened just based on the type, we're going to default to
-            # asking the variable bridge, at the risk of a false negative.
-            if is_variable_bridged(b, S)
-                bridge = Variable.concrete_bridge_type(b, S)
-                return MOI.supports(recursive_model(b), attr, bridge)
-            else
-                bridge = Constraint.concrete_bridge_type(b, F, S)
-                return MOI.supports(recursive_model(b), attr, bridge)
-            end
-        else
-            # If S doesn't need to be bridged, it usually means that either the
-            # solver supports add_constrained_variable, or it supports free
-            # variables and add_constraint.
-            #
-            # In some cases, it might be that the solver supports
-            # add_constrained_variable, but ends up bridging add_constraint.
-            # Because MOI lacks the ability to tell which one was called based
-            # on the index type, asking the model might give a false negative
-            # (we support the attribute via add_constrained_variable, but the
-            # bridge doesn't via add_constraint because it will be bridged).
-            return MOI.supports(b.model, attr, MOI.ConstraintIndex{F,S})
+        # supports should return true if it is possible to support the
+        # attribute at any point, even if it does not currently support it.
+        #
+        # So check if the model supports it if we added via `add_constraint` and
+        # didn't bridge:
+        ret = MOI.supports(b.model, attr, MOI.ConstraintIndex{F,S})
+        # And if we added it via a variable bridge:
+        if is_variable_bridged(b, S)
+            bridge = Variable.concrete_bridge_type(b, S)
+            ret |= MOI.supports(recursive_model(b), attr, bridge)
         end
-    else
-        # These are normal add_constraints, so we just check if they are
-        # bridged.
+        # And if we added it via a constraint bridge:
         if is_bridged(b, F, S)
             bridge = Constraint.concrete_bridge_type(b, F, S)
-            return MOI.supports(recursive_model(b), attr, bridge)
-        else
-            return MOI.supports(b.model, attr, MOI.ConstraintIndex{F,S})
+            ret |= MOI.supports(recursive_model(b), attr, bridge)
         end
+        return ret
+    elseif is_bridged(b, F, S)
+        bridge = Constraint.concrete_bridge_type(b, F, S)
+        return MOI.supports(recursive_model(b), attr, bridge)
+    else
+        return MOI.supports(b.model, attr, MOI.ConstraintIndex{F,S})
     end
 end
 

test/Bridges/bridge_optimizer.jl

@@ -903,10 +903,7 @@ function test_Issue1992_supports_ConstraintDualStart_VariableIndex()
     model = MOI.Bridges.full_bridge_optimizer(_Issue1992(true), Float64)
     x, _ = MOI.add_constrained_variables(model, MOI.Nonpositives(1))
     c = MOI.add_constraint(model, MOI.VectorOfVariables(x), MOI.Nonnegatives(1))
-    # !!! warning
-    #     This test is broken with a false negative. See the discussion in
-    #     PR#1992.
-    @test_broken MOI.supports(model, MOI.ConstraintDualStart(), typeof(c))
+    @test MOI.supports(model, MOI.ConstraintDualStart(), typeof(c))
     return
 end
 
@@ -919,11 +916,7 @@ function test_bridge_supports_issue_1992()
         MOI.VectorOfVariables([x]),
         MOI.Nonpositives(1),
     )
-    # !!! warning
-    #     This test is broken with a false negative. (Getting and setting the
-    #     attribute works, even though supports is false) See the discussion in
-    #     PR#1992.
-    @test_broken MOI.supports(model, MOI.ConstraintDualStart(), typeof(c))
+    @test MOI.supports(model, MOI.ConstraintDualStart(), typeof(c))
     @test MOI.get(model, MOI.ConstraintDualStart(), c) === nothing
     MOI.set(model, MOI.ConstraintDualStart(), c, [1.0])
     @test MOI.get(model, MOI.ConstraintDualStart(), c) == [1.0]