Fix setLogfile method to handle None path (#813)

* Fix setLogfile method to handle None path

* Add new test for model setLogFile and fix setLogFile(None) error

* adjust log file handling in Model class

---------

Co-authored-by: Mohammed Ghannam <ghannam@zib.de>

Author: liangbug

CHANGELOG.md

@@ -4,8 +4,10 @@
 ### Added
 - Added method for adding piecewise linear constraints
 - Add SCIP function SCIPgetTreesizeEstimation and wrapper getTreesizeEstimation
-- Add recipes sub-package
+- New test for model setLogFile
 ### Fixed
+- Fixed model.setLogFile(None) error
+- Add recipes sub-package
 - Fixed "weakly-referenced object no longer exists" when calling dropEvent in test_customizedbenders
 - Fixed incorrect writing/printing when user had a non-default locale
 ### Changed

src/pyscipopt/scip.pxi

@@ -4974,8 +4974,11 @@ cdef class Model:
         """sets the log file name for the currently installed message handler
         :param path: name of log file, or None (no log)
         """
-        c_path = str_conversion(path) if path else None
-        SCIPsetMessagehdlrLogfile(self._scip, c_path)
+        if path:
+            c_path = str_conversion(path)
+            SCIPsetMessagehdlrLogfile(self._scip, c_path)
+        else:
+            SCIPsetMessagehdlrLogfile(self._scip, NULL)
 
     # Parameter Methods
 

tests/test_model.py

@@ -1,4 +1,5 @@
 import pytest
+import os
 
 from pyscipopt import Model, SCIP_STAGE
 
@@ -300,6 +301,39 @@ def test_getTreesizeEstimation():
     m.optimize()
 
     assert m.getTreesizeEstimation() > 0
+
+def test_setLogFile():
+    m = Model()
+    x = m.addVar("x", vtype="I")
+    y = m.addVar("y", vtype="I")
+    m.addCons(x + y == 1)
+    m.setObjective(2*x+y)
+    
+    log_file_name = "test_setLogFile.log"
+    m.setLogfile(log_file_name)
+    assert os.path.exists(log_file_name)
+    
+    m.optimize()
+    del m
+    assert os.path.getsize(log_file_name) > 0
+    os.remove(log_file_name)
+
+def test_setLogFile_none():
+    m = Model()
+    x = m.addVar("x", vtype="I")
+    y = m.addVar("y", vtype="I")
+    m.addCons(x + y == 1)
+    m.setObjective(2*x+y)
+    
+    log_file_name = "test_setLogfile_none.log"
+    m.setLogfile(log_file_name)
+    assert os.path.exists(log_file_name)
+    
+    m.setLogfile(None)
+    m.optimize()
+    del m
+    assert os.path.getsize(log_file_name) == 0
+    os.remove(log_file_name)
 
 def test_locale():
     import locale
@@ -315,4 +349,3 @@ def test_locale():
 
     with open("model.cip") as file:
         assert "1,1" not in file.read()
-