Add Variable bridges to use runtests without unbridged_variable

src/Bridges/Bridges.jl

@@ -144,7 +144,7 @@ MOI.get_fallback(model::MOI.ModelLike, ::ListOfNonstandardBridges) = Type[]
 
 include("precompile.jl")
 
-function _test_structural_identical(a::MOI.ModelLike, b::MOI.ModelLike)
+function _test_structural_identical(a::MOI.ModelLike, b::MOI.ModelLike; allow_constraint_function_error::Bool = false)
     # Test that the variables are the same. We make the strong assumption that
     # the variables are added in the same order to both models.
     a_x = MOI.get(a, MOI.ListOfVariableIndices())
@@ -190,7 +190,15 @@ function _test_structural_identical(a::MOI.ModelLike, b::MOI.ModelLike)
         Test.@test MOI.supports_constraint(b, F, S)
         # Check that each function in `b` matches a function in `a`
         for ci in MOI.get(b, MOI.ListOfConstraintIndices{F,S}())
-            f_b = MOI.get(b, MOI.ConstraintFunction(), ci)
+            try
+                f_b = MOI.get(b, MOI.ConstraintFunction(), ci)
+            catch err
+                if allow_constraint_function_error && err isa MOI.GetAttributeNotAllowed{MOI.ConstraintFunction}
+                    continue
+                else
+                    rethrow(err)
+                end
+            end
             f_b = MOI.Utilities.map_indices(x_map, f_b)
             s_b = MOI.get(b, MOI.ConstraintSet(), ci)
             # We don't care about the order that constraints are added, only
@@ -253,6 +261,7 @@ function runtests(
     constraint_start = 1.2,
     eltype = Float64,
     print_inner_model::Bool = false,
+    allow_outer_constraint_function_error::Bool = false,
 )
     # Load model and bridge it
     inner = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{eltype}())
@@ -267,7 +276,7 @@ function runtests(
     # Load a non-bridged input model, and check that getters are the same.
     test = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{eltype}())
     input_fn(test)
-    _test_structural_identical(test, model)
+    _test_structural_identical(test, model; allow_constraint_function_error = allow_outer_constraint_function_error)
     # Load a bridged target model, and check that getters are the same.
     target = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{eltype}())
     output_fn(target)