fix tests

Author: RobbieKiwi

linopy/model.py

@@ -116,9 +116,15 @@ def wrapper(*args: P.args, **kwargs: P.kwargs) -> R:
         constant = self.objective.expression.const
         model.objective.expression = self.objective.expression.drop_constant()
         args = (model, *args[1:])  # type: ignore
-        result = func(*args, **kwargs)
 
-        # Re-add the constant term
+        try:
+            result = func(*args, **kwargs)
+        except Exception as e:
+            # Even if there is an exception, make sure the model returns to it's original state
+            model.objective.expression = model.objective.expression + constant
+            raise e
+
+        # Re-add the constant term to return the model objective to the original expression
         model.objective.expression = model.objective.expression + constant
         if model.objective.value is not None:
             model.objective.set_value(model.objective.value + constant)

test/test_model.py

@@ -82,9 +82,8 @@ def test_objective() -> None:
     assert m.objectiverange.min() == 2
     assert m.objectiverange.max() == 2
 
-    # test objective with constant which is not supported
-    with pytest.raises(ValueError):
-        m.objective = m.objective + 3
+    # test objective with constant which is supported
+    m.objective = m.objective + 3
 
 
 def test_remove_variable() -> None:

test/test_objective.py

@@ -192,5 +192,4 @@ def test_repr(linear_objective: Objective, quadratic_objective: Objective) -> No
 def test_objective_constant() -> None:
     m = Model()
     linear_expr = LinearExpression(None, m) + 1
-    with pytest.raises(ValueError):
-        m.objective = Objective(linear_expr, m)
+    m.objective = Objective(linear_expr, m)

test/test_optimization.py

@@ -956,7 +956,7 @@ def test_model_resolve(
     assert np.isclose(model.objective.value or 0, 5.25)
 
 
-def test_model_with_constant_in_objective(model: Model) -> None:
+def test_model_with_constant_in_objective_feasible(model: Model) -> None:
     objective = model.objective.expression + 1
     model.add_objective(expr=objective, overwrite=True)
 
@@ -969,6 +969,35 @@ def test_model_with_constant_in_objective(model: Model) -> None:
     assert model.objective.expression.solution == 4.3
 
 
+def test_model_with_constant_in_objective_infeasible(model: Model) -> None:
+    objective = model.objective.expression + 1
+    model.add_objective(expr=objective, overwrite=True)
+    model.add_constraints([(1, "x")], "<=", 0)
+    model.add_constraints([(1, "y")], "<=", 0)
+
+    with pytest.warns(ConstantInObjectiveWarning):
+        status, condition = model.solve(solver_name="highs")
+
+    assert condition == "infeasible"
+    # Even though the problem was not solved, the constant term should still be accessible
+    assert model.objective.expression.const == 1
+
+
+def test_model_with_constant_in_objective_error(model: Model) -> None:
+    objective = model.objective.expression + 1
+    model.add_objective(expr=objective, overwrite=True)
+    model.add_constraints([(1, "x")], "<=", 0)
+    model.add_constraints([(1, "y")], "<=", 0)
+
+    try:
+        status, condition = model.solve(solver_name="apples")
+    except AssertionError:
+        pass
+
+    # Even if something goes wrong, the model objective should return to the correct state
+    assert model.objective.expression.const == 1
+
+
 @pytest.mark.parametrize(
     "solver,io_api,explicit_coordinate_names", [p for p in params if "direct" not in p]
 )