Fix handling of solution statuses for multiple results (#393)

Project.toml

@@ -1,7 +1,7 @@
 name = "Gurobi"
 uuid = "2e9cd046-0924-5485-92f1-d5272153d98b"
 repo = "https://github.com/jump-dev/Gurobi.jl"
-version = "0.9.8"
+version = "0.9.9"
 
 [deps]
 CEnum = "fa961155-64e5-5f13-b03f-caf6b980ea82"

src/MOI_wrapper.jl

@@ -2474,21 +2474,22 @@ end
 
 function MOI.get(model::Optimizer, attr::MOI.PrimalStatus)
     _throw_if_optimize_in_progress(model, attr)
-    if attr.N != 1
-        return MOI.NO_SOLUTION
-    end
     term = MOI.get(model, MOI.TerminationStatus())
     if term == MOI.DUAL_INFEASIBLE || term == MOI.INFEASIBLE_OR_UNBOUNDED
-        if _has_primal_ray(model)
+        if attr.N != 1
+            return MOI.NO_SOLUTION
+        elseif _has_primal_ray(model)
             return MOI.INFEASIBILITY_CERTIFICATE
         else
             return MOI.NO_SOLUTION
         end
     end
+    # Check SolCount explicitly instead of ResultCount to avoid returning 1 when
+    # there is a certiticate.
     valueP = Ref{Cint}()
     ret = GRBgetintattr(model, "SolCount", valueP)
     _check_ret(model, ret)
-    return valueP[] > 0 ? MOI.FEASIBLE_POINT : MOI.NO_SOLUTION
+    return 1 <= attr.N <= valueP[] ? MOI.FEASIBLE_POINT : MOI.NO_SOLUTION
 end
 
 function _has_dual_ray(model::Optimizer)
@@ -2519,6 +2520,8 @@ function MOI.get(model::Optimizer, attr::MOI.DualStatus)
             return MOI.NO_SOLUTION
         end
     end
+    # Check SolCount explicitly instead of ResultCount to avoid returning 1 when
+    # there is a certiticate.
     valueP = Ref{Cint}()
     ret = GRBgetintattr(model, "SolCount", valueP)
     _check_ret(model, ret)

test/MOI/MOI_wrapper.jl

@@ -1572,6 +1572,8 @@ function test_multiple_solutions()
             MOI.ResultIndexBoundsError,
             MOI.get(model, MOI.ObjectiveValue(n)),
         )
+        @test MOI.get(model, MOI.PrimalStatus(n)) == MOI.NO_SOLUTION
+        @test MOI.get(model, MOI.DualStatus(n)) == MOI.NO_SOLUTION
     end
     for n = 1:RC
         xn = MOI.get(model, MOI.VariablePrimal(n), x)
@@ -1581,6 +1583,8 @@ function test_multiple_solutions()
             item_values' * xn,
             atol=1e-6,
         )
+        @test MOI.get(model, MOI.PrimalStatus(n)) == MOI.FEASIBLE_POINT
+        @test MOI.get(model, MOI.DualStatus(n)) == MOI.NO_SOLUTION
     end
 end