Address logging case of no user-specified options

pyomo/contrib/pyros/pyros.py

@@ -227,19 +227,41 @@ def _log_config_user_values(
             ):
         """
         Log explicitly set PyROS solver options.
+
+        If there are no such options, or all such options
+        are to be excluded from consideration, then nothing is logged.
+
+        Parameters
+        ----------
+        logger : logging.Logger
+            Logger for the solver options.
+        config : ConfigDict
+            PyROS solver options.
+        exclude_options : None or iterable of str, optional
+            Options (keys of the ConfigDict) to exclude from
+            logging. If `None` passed, then the names of the
+            required arguments to ``self.solve()`` are skipped.
+        **log_kwargs : dict, optional
+            Keyword arguments to each statement of ``logger.log()``.
         """
         if exclude_options is None:
-            exclude_options = self._DEFAULT_CONFIG_USER_OPTIONS
+            exclude_options = set(self._DEFAULT_CONFIG_USER_OPTIONS)
+        else:
+            exclude_options = set(exclude_options)
 
-        logger.log(msg="User-provided solver options:", **log_kwargs)
-        for val in config.user_values():
-            val_name, val_value = val.name(), val.value()
-            # note: first clause of if statement
+        user_values = list(filter(
+            # note: first clause of logical expression
             #       accounts for bug(?) causing an iterate
             #       of user_values to be the config dict itself
-            if val_name and val_name not in exclude_options:
+            lambda val: bool(val.name()) and val.name() not in exclude_options,
+            config.user_values(),
+        ))
+        if user_values:
+            logger.log(msg="User-provided solver options:", **log_kwargs)
+            for val in user_values:
+                val_name, val_value = val.name(), val.value()
                 logger.log(msg=f" {val_name}={val_value!r}", **log_kwargs)
-        logger.log(msg="-" * self._LOG_LINE_LENGTH, **log_kwargs)
+            logger.log(msg="-" * self._LOG_LINE_LENGTH, **log_kwargs)
 
     def _log_config(self, logger, config, exclude_options=None, **log_kwargs):
         """

pyomo/contrib/pyros/tests/test_grcs.py

@@ -3370,6 +3370,31 @@ class TestPyROSSolverLogIntros(unittest.TestCase):
     Test logging of introductory information by PyROS solver.
     """
 
+    def test_log_config_user_values_all_default(self):
+        """
+        Test method for logging config user values logs
+        nothing if all values are set to default.
+        """
+        pyros_solver = SolverFactory("pyros")
+        config = pyros_solver.CONFIG(dict(
+            # mandatory arguments to PyROS solver.
+            # by default, these should be excluded from the printout
+            first_stage_variables=[],
+            second_stage_variables=[],
+            uncertain_params=[],
+            uncertainty_set=BoxSet([[1, 2]]),
+            local_solver=SimpleTestSolver(),
+            global_solver=SimpleTestSolver(),
+            # no optional arguments
+        ))
+        with LoggingIntercept(logger=logger, level=logging.INFO) as LOG:
+            pyros_solver._log_config_user_values(
+                logger=logger,
+                config=config,
+                level=logging.INFO,
+            )
+        self.assertEqual(LOG.getvalue(), "")
+
     def test_log_config_user_values(self):
         """
         Test method for logging config user values.