Fix bug in solution_summary: duals can be things other than scalars

src/solution_summary.jl

@@ -21,7 +21,7 @@ struct _SolutionSummary{T}
     relative_gap::Union{Missing,T}
     dual_objective_value::Union{Missing,T}
     primal_solution::Union{Missing,Dict{String,T}}
-    dual_solution::Union{Missing,Dict{String,T}}
+    dual_solution::Union{Missing,Dict{String,Any}}
     # Work counters
     solve_time::Union{Missing,Float64}
     barrier_iterations::Union{Missing,Int}
@@ -232,7 +232,7 @@ function _get_solution_dict(model, result)
 end
 
 function _get_constraint_dict(model, result)
-    dict = Dict{String,value_type(typeof(model))}()
+    dict = Dict{String,Any}()
     for (F, S) in list_of_constraint_types(model)
         for constraint in all_constraints(model, F, S)
             constraint_name = name(constraint)

test/test_solution_summary.jl

@@ -164,4 +164,45 @@ function test_solution_summary()
     return
 end
 
+function test_solution_summary_vector_dual()
+    model = Model() do
+        return MOI.Utilities.MockOptimizer(MOI.Utilities.Model{Float64}())
+    end
+    @variable(model, x[1:2])
+    @constraint(model, c, x >= 0)
+    optimize!(model)
+    mock = unsafe_backend(model)
+    MOI.set(mock, MOI.TerminationStatus(), MOI.OPTIMAL)
+    MOI.set(mock, MOI.RawStatusString(), "solver specific string")
+    MOI.set(mock, MOI.ResultCount(), 1)
+    MOI.set(mock, MOI.PrimalStatus(), MOI.FEASIBLE_POINT)
+    MOI.set(mock, MOI.DualStatus(), MOI.FEASIBLE_POINT)
+    MOI.set(mock, MOI.VariablePrimal(), optimizer_index.(x), [1.0, 2.0])
+    MOI.set(mock, MOI.ConstraintDual(), optimizer_index.(c), [3.0, 4.0])
+    ret = """
+    * Solver : Mock
+
+    * Status
+      Result count       : 1
+      Termination status : OPTIMAL
+      Message from the solver:
+      "solver specific string"
+
+    * Candidate solution (result #1)
+      Primal status      : FEASIBLE_POINT
+      Dual status        : FEASIBLE_POINT
+      Objective value    : 0.00000e+00
+      Dual objective value : 0.00000e+00
+      Primal solution :
+        x[1] : 1.00000e+00
+        x[2] : 2.00000e+00
+      Dual solution :
+        c : [3.00000e+00,4.00000e+00]
+
+    * Work counters
+    """
+    @test sprint(show, solution_summary(model; verbose = true)) == ret
+    return
 end
+
+end  # module