Merge pull request #502 from JuliaOpt/bl/fix499

Test InexactError thrown for bad objective function type

Author: blegat

src/Test/UnitTests/objectives.jl

@@ -56,6 +56,31 @@ function feasibility_sense(model::MOI.ModelLike, config::TestConfig)
 end
 unittests["feasibility_sense"] = feasibility_sense
 
+"""
+    get_objective_function(model::MOI.ModelLike, config::TestConfig)
+
+Test get objective function.
+"""
+function get_objective_function(model::MOI.ModelLike, config::TestConfig)
+    MOI.empty!(model)
+    @test MOI.isempty(model)
+    obj_attr = MOI.ObjectiveFunction{MOI.ScalarAffineFunction{Float64}}()
+    @test MOI.supports(model, obj_attr)
+    MOIU.loadfromstring!(model,"""
+        variables: x
+        minobjective: 2.0x + 1.0
+    """)
+    x = MOI.get(model, MOI.VariableIndex, "x")
+    expected_obj_fun = MOI.ScalarAffineFunction([MOI.ScalarAffineTerm(2.0, x)],
+                                                1.0)
+    @test_throws InexactError begin
+        MOI.get(model, MOI.ObjectiveFunction{MOI.SingleVariable}())
+    end
+    obj_fun = MOI.get(model, obj_attr)
+    @test obj_fun ≈ expected_obj_fun
+end
+unittests["get_objective_function"] = get_objective_function
+
 """
     solve_constant_obj(model::MOI.ModelLike, config::TestConfig)
 

src/Utilities/model.jl

@@ -233,7 +233,11 @@ function MOI.get(model::AbstractModel, ::MOI.ObjectiveFunctionType)
 end
 function MOI.get(model::AbstractModel, ::MOI.ObjectiveFunction{T})::T where T
     if typeof(model.objective) != T
-        throw(InexactError())
+        if VERSION >= v"0.7-"
+            throw(InexactError(:get, T, model.objective))
+        else
+            throw(InexactError())
+        end
     end
     model.objective
 end