KNITROAMPL: use \$KNITRODIR/knitroampl/knitroampl for executable

pyomo/solvers/plugins/solvers/KNITROAMPL.py

@@ -7,6 +7,7 @@
 # software.  This software is distributed under the 3-clause BSD License.
 # ____________________________________________________________________________________
 import logging
+import os
 
 from pyomo.common import Executable
 from pyomo.common.collections import Bunch
@@ -64,17 +65,25 @@ def __init__(self, **kwds):
         self._capabilities.sos2 = False
 
     def _default_executable(self):
-        try:
-            # If knitro Python package is available, use the executable it contains
-            import knitro
+        executable = None
+        knitrodir = os.environ.get('KNITRODIR')
+        if knitrodir:
+            knitroampl_path = pathlib.Path(knitrodir) / 'knitroampl' / 'knitroampl'
+            executable = Executable(str(knitroampl_path))
+        if not executable:
+            try:
+                # If knitro Python package is available, use the executable it contains
+                import knitro
 
-            package_knitroampl_path = (
-                pathlib.Path(knitro.__file__).resolve().parent
-                / 'knitroampl'
-                / 'knitroampl'
-            )
-            executable = Executable(str(package_knitroampl_path))
-        except ModuleNotFoundError:
+                package_knitroampl_path = (
+                    pathlib.Path(knitro.__file__).resolve().parent
+                    / 'knitroampl'
+                    / 'knitroampl'
+                )
+                executable = Executable(str(package_knitroampl_path))
+            except ModuleNotFoundError:
+                pass
+        if not executable:
             # Otherwise, search usual path list
             executable = Executable('knitroampl')
         if not executable:

pyomo/solvers/tests/checks/test_KNITROAMPL.py

@@ -7,7 +7,10 @@
 # software.  This software is distributed under the 3-clause BSD License.
 # ____________________________________________________________________________________
 
+import os
+
 from pyomo.common import unittest
+from pyomo.common.tempfiles import TempfileManager
 from pyomo.environ import (
     ConcreteModel,
     Var,
@@ -23,6 +26,32 @@
 knitroampl_available = SolverFactory('knitroampl').available(False)
 
 
+class TestKNITROAMPLDefaultExecutable(unittest.TestCase):
+    def test_default_executable_from_KNITRODIR(self):
+        with TempfileManager.new_context() as tempfile:
+            knitrodir = tempfile.create_tempdir()
+            exe = os.path.join(knitrodir, 'knitroampl', 'knitroampl')
+            # This makes a fake executable with the correct permissions
+            # so KNITRO actually recognizes it
+            os.mkdir(os.path.dirname(exe))
+            with open(exe, 'w'):
+                pass
+            os.chmod(exe, 0o755)
+
+            orig = os.environ.get('KNITRODIR')
+            os.environ['KNITRODIR'] = knitrodir
+            try:
+                opt = SolverFactory('knitroampl')
+                self.assertEqual(
+                    os.path.realpath(opt._default_executable()), os.path.realpath(exe)
+                )
+            finally:
+                if orig is None:
+                    del os.environ['KNITRODIR']
+                else:
+                    os.environ['KNITRODIR'] = orig
+
+
 @unittest.skipIf(not knitroampl_available, "The 'knitroampl' command is not available")
 @unittest.pytest.mark.solver("knitroampl")
 class TestKNITROAMPLInterface(unittest.TestCase):