[Bridges] fix get ListOfVariableIndices when there is a chain of bridges (#2716)

Author: odow

src/Bridges/Variable/map.jl

@@ -174,7 +174,6 @@ function number_of_variables(map::Map)
                 num += length_of_vector_of_variables(map, MOI.VariableIndex(-i))
             end
         end
-        count(bridge -> bridge !== nothing, map.bridges)
     end
     return num
 end

src/Bridges/bridge_optimizer.jl

@@ -760,6 +760,11 @@ function _get_all_including_bridged(
     ret = MOI.VariableIndex[]
     for inner_variable in MOI.get(b.model, attr)
         outer_variable = get(inner_to_outer, inner_variable, missing)
+        # If there is a chain of variable bridges, the `outer_variable` may need
+        # to be mapped.
+        while haskey(inner_to_outer, outer_variable)
+            outer_variable = inner_to_outer[outer_variable]
+        end
         if ismissing(outer_variable)
             # inner_variable does not exist in inner_to_outer, which means that
             # it is not bridged. Pass through unchanged.

test/Bridges/bridge_optimizer.jl

@@ -1422,6 +1422,36 @@ function test_fallback_delete_objective_bridge()
     return
 end
 
+struct Model2714 <: MOI.ModelLike
+    dimensions::Vector{Int}
+    Model2714() = new(Int[])
+end
+
+MOI.is_empty(model::Model2714) = isempty(model.dimensions)
+
+function MOI.supports_add_constrained_variables(
+    ::Model2714,
+    ::Type{MOI.Nonnegatives},
+)
+    return true
+end
+
+function MOI.add_constrained_variables(model::Model2714, set::MOI.Nonnegatives)
+    n = MOI.dimension(set)
+    x = MOI.VariableIndex(sum(model.dimensions) .+ (1:n))
+    push!(model.dimensions, n)
+    F, S = MOI.VectorOfVariables, MOI.Nonnegatives
+    return x, MOI.ConstraintIndex{F,S}(length(model.dimensions))
+end
+
+function test_issue_2714()
+    model = MOI.instantiate(Model2714; with_bridge_type = Float64)
+    t, _ = MOI.add_constrained_variable(model, MOI.LessThan(10.0))
+    @test MOI.get(model, MOI.NumberOfVariables()) == 1
+    @test MOI.get(model, MOI.ListOfVariableIndices()) == [t]
+    return
+end
+
 end  # module
 
 TestBridgeOptimizer.runtests()