fix: no sol file for gurobi

doc/release_notes.rst

@@ -6,7 +6,7 @@ Upcoming Version
 
 * Support for warmstart in HiGHS using basis or solution files, including support for writing basis and solution files of a solved model.
 * Linopy now uses mypy for type checking allowing for a more secure and stable code base.
-
+* The creation of solution files with gurobi, scip and mindopt is now supported.
 
 Version 0.3.11
 --------------

linopy/solvers.py

@@ -577,6 +577,13 @@ def run_cplex(
 
     with contextlib.suppress(cplex.exceptions.errors.CplexSolverError):
         m.solve()
+
+    if solution_fn is not None:
+        try:
+            m.solution.write(path_to_string(solution_fn))
+        except cplex.exceptions.errors.CplexSolverError as err:
+            logger.info("Unable to save solution file. Raised error: %s", err)
+
     condition = m.solution.get_status_string()
     termination_condition = CONDITION_MAP.get(condition, condition)
     status = Status.from_termination_condition(termination_condition)
@@ -686,6 +693,12 @@ def run_gurobi(
             except gurobipy.GurobiError as err:
                 logger.info("No model basis stored. Raised error: %s", err)
 
+        if solution_fn is not None and solution_fn.suffix == ".sol":
+            try:
+                m.write(path_to_string(solution_fn))
+            except gurobipy.GurobiError as err:
+                logger.info("Unable to save solution file. Raised error: %s", err)
+
         condition = m.status
         termination_condition = CONDITION_MAP.get(condition, condition)
         status = Status.from_termination_condition(termination_condition)
@@ -773,6 +786,12 @@ def run_scip(
     if basis_fn:
         logger.warning("Basis not implemented for SCIP")
 
+    if solution_fn:
+        try:
+            m.writeSol(m.getBestSol(), filename=path_to_string(solution_fn))
+        except FileNotFoundError as err:
+            logger.warning("Unable to save solution file. Raised error: %s", err)
+
     condition = m.getStatus()
     termination_condition = CONDITION_MAP.get(condition, condition)
     status = Status.from_termination_condition(termination_condition)
@@ -864,6 +883,12 @@ def run_xpress(
         except Exception as err:
             logger.info("No model basis stored. Raised error: %s", err)
 
+    if solution_fn is not None:
+        try:
+            m.writeSolution(path_to_string(solution_fn))
+        except Exception as err:
+            logger.info("Unable to save solution file. Raised error: %s", err)
+
     condition = m.getProbStatusString()
     termination_condition = CONDITION_MAP.get(condition, condition)
     status = Status.from_termination_condition(termination_condition)
@@ -1164,6 +1189,12 @@ def run_copt(
         except coptpy.CoptError as err:
             logger.info("No model basis stored. Raised error: %s", err)
 
+    if solution_fn:
+        try:
+            m.write(path_to_string(solution_fn))
+        except coptpy.CoptError as err:
+            logger.info("No model solution stored. Raised error: %s", err)
+
     condition = m.LpStatus if model.type in ["LP", "QP"] else m.MipStatus
     termination_condition = CONDITION_MAP.get(condition, condition)
     status = Status.from_termination_condition(termination_condition)
@@ -1256,6 +1287,12 @@ def run_mindopt(
         except mindoptpy.MindoptError as err:  # type: ignore
             logger.info("No model basis stored. Raised error: %s", err)
 
+    if solution_fn:
+        try:
+            m.write(path_to_string(solution_fn))
+        except mindoptpy.MindoptError as err:  # type: ignore
+            logger.info("No model solution stored. Raised error: %s", err)
+
     condition = m.status
     termination_condition = CONDITION_MAP.get(condition, condition)
     status = Status.from_termination_condition(termination_condition)

test/test_optimization.py

@@ -459,12 +459,17 @@ def test_set_files(tmp_path, model, solver, io_api):
 def test_set_files_and_keep_files(tmp_path, model, solver, io_api):
     status, condition = model.solve(
         solver,
+        io_api=io_api,
         problem_fn=tmp_path / "problem.lp",
         solution_fn=tmp_path / "solution.sol",
         log_fn=tmp_path / "logging.log",
         keep_files=True,
     )
     assert status == "ok"
+    if io_api != "direct":
+        assert (tmp_path / "problem.lp").exists()
+        assert (tmp_path / "solution.sol").exists()
+    assert (tmp_path / "logging.log").exists()
 
 
 @pytest.mark.parametrize("solver,io_api", params)