fix: remove highs log file default (#445)

* fix: remove highs log file default

* docs: add release note

---------

Co-authored-by: Fabian Hofmann <fab.hof@gmx.de>

Author: ollie-bell

doc/release_notes.rst

@@ -6,6 +6,8 @@ Upcoming Version
 
 **Bug Fixes**
 
+* Remove default highs log file when `log_fn=None` and `io_api="direct"`. This caused `log_file` in
+`solver_options` to be ignored.
 * Fix the parsing of solutions returned by the CBC solver when setting a MIP duality
   gap tolerance.
 * Improve the mapping of termination conditions for the SCIP solver

linopy/solvers.py

@@ -752,9 +752,6 @@ def solve_problem_from_model(
 
         h = model.to_highspy(explicit_coordinate_names=explicit_coordinate_names)
 
-        if log_fn is None and model is not None:
-            log_fn = model.solver_dir / "highs.log"
-
         return self._solve(
             h,
             solution_fn,