Use os.makedirs to create parent dirs for solution_fn since this is o…

…s independent

linopy/solvers.py

@@ -171,8 +171,7 @@ def run_cbc(
     if basis_fn:
         command += f"-basisO {basis_fn} "
 
-    if not os.path.exists(solution_fn):
-        os.mknod(solution_fn)
+    os.makedirs(os.path.dirname(solution_fn), exist_ok=True)
 
     command = command.strip()
 
@@ -263,6 +262,8 @@ def run_glpk(
     problem_fn = model.to_file(problem_fn)
     suffix = problem_fn.suffix[1:]
 
+    os.makedirs(os.path.dirname(solution_fn), exist_ok=True)
+
     # TODO use --nopresol argument for non-optimal solution output
     command = f"glpsol --{suffix} {problem_fn} --output {solution_fn} "
     if log_fn is not None:

test/test_optimization.py

@@ -555,6 +555,13 @@ def test_basis_and_warmstart(tmp_path, model, solver, io_api):
     model.solve(solver, warmstart_fn=basis_fn)
 
 
+@pytest.mark.parametrize("solver,io_api", params)
+def test_solution_fn_parent_dir_doesnt_exist(model, solver, io_api, tmp_path):
+    solution_fn = tmp_path / "non_existent_dir" / "non_existent_file"
+    status, condition = model.solve(solver, io_api=io_api, solution_fn=solution_fn)
+    assert status == "ok"
+
+
 # def init_model_large():
 #     m = Model()
 #     time = pd.Index(range(10), name="time")