Merge pull request #3596 from michaelbynum/string_issue

Allow default and custom messages in derived classes from `PyomoException`

Author: jsiirola

pyomo/common/errors.py

@@ -117,17 +117,19 @@ class ApplicationError(Exception):
     An exception used when an external application generates an error.
     """
 
-    pass
-
 
 class PyomoException(Exception):
     """
     Exception class for other Pyomo exceptions to inherit from,
     allowing Pyomo exceptions to be caught in a general way
     (e.g., in other applications that use Pyomo).
+    Subclasses can define a class-level `default_message` attribute.
     """
 
-    pass
+    def __init__(self, *args):
+        if not args and getattr(self, 'default_message', None):
+            args = (self.default_message,)
+        return super().__init__(*args)
 
 
 class DeferredImportError(ImportError):
@@ -137,8 +139,6 @@ class DeferredImportError(ImportError):
 
     """
 
-    pass
-
 
 class DeveloperError(PyomoException, NotImplementedError):
     """
@@ -163,8 +163,6 @@ class InfeasibleConstraintException(PyomoException):
     the course of range reduction).
     """
 
-    pass
-
 
 class IterationLimitError(PyomoException, RuntimeError):
     """A subclass of :py:class:`RuntimeError`, raised by an iterative method
@@ -182,16 +180,12 @@ class IntervalException(PyomoException, ValueError):
     Exception class used for errors in interval arithmetic.
     """
 
-    pass
-
 
 class InvalidValueError(PyomoException, ValueError):
     """
     Exception class used for value errors in compiled model representations
     """
 
-    pass
-
 
 class MouseTrap(PyomoException, NotImplementedError):
     """
@@ -218,17 +212,13 @@ def __str__(self):
 class NondifferentiableError(PyomoException, ValueError):
     """A Pyomo-specific ValueError raised for non-differentiable expressions"""
 
-    pass
-
 
 class TempfileContextError(PyomoException, IndexError):
     """A Pyomo-specific IndexError raised when attempting to use the
     TempfileManager when it does not have a currently active context.
 
     """
 
-    pass
-
 
 class TemplateExpressionError(ValueError):
     """Special ValueError raised by getitem for template arguments

pyomo/common/tests/test_errors.py

@@ -10,13 +10,17 @@
 #  ___________________________________________________________________________
 
 import pyomo.common.unittest as unittest
-from pyomo.common.errors import format_exception
+from pyomo.common.errors import format_exception, PyomoException
 
 
 class LocalException(Exception):
     pass
 
 
+class CustomLocalException(PyomoException):
+    default_message = 'Default message.'
+
+
 class TestFormatException(unittest.TestCase):
     def test_basic_message(self):
         self.assertEqual(format_exception("Hello world"), "Hello world")
@@ -137,3 +141,14 @@ def test_basic_message_formatted_epilog(self):
             "        inevitably wrap onto another line.\n"
             "Hello world:\n    This is an epilog:",
         )
+
+
+class TestPyomoException(unittest.TestCase):
+    def test_default_message(self):
+        exception = CustomLocalException()
+        self.assertIn("Default message.", str(exception))
+
+    def test_custom_message_override(self):
+        exception = CustomLocalException("Non-default message.")
+        self.assertNotIn("Default message.", str(exception))
+        self.assertIn("Non-default message.", str(exception))

pyomo/contrib/solver/common/util.py

@@ -16,53 +16,47 @@
 
 
 class NoFeasibleSolutionError(PyomoException):
-    def __init__(self):
-        super().__init__(
-            'A feasible solution was not found, so no solution can be loaded. '
-            'Please set opt.config.load_solutions=False and check '
-            'results.solution_status and '
-            'results.incumbent_objective before loading a solution.'
-        )
+    default_message = (
+        'A feasible solution was not found, so no solution can be loaded. '
+        'Please set opt.config.load_solutions=False and check '
+        'results.solution_status and '
+        'results.incumbent_objective before loading a solution.'
+    )
 
 
 class NoOptimalSolutionError(PyomoException):
-    def __init__(self):
-        super().__init__(
-            'Solver did not find the optimal solution. Set '
-            'opt.config.raise_exception_on_nonoptimal_result = False to bypass this error.'
-        )
+    default_message = (
+        'Solver did not find the optimal solution. Set '
+        'opt.config.raise_exception_on_nonoptimal_result = False to bypass this error.'
+    )
 
 
 class NoSolutionError(PyomoException):
-    def __init__(self):
-        super().__init__(
-            'Solution loader does not currently have a valid solution. Please '
-            'check results.termination_condition and/or results.solution_status.'
-        )
+    default_message = (
+        'Solution loader does not currently have a valid solution. Please '
+        'check results.termination_condition and/or results.solution_status.'
+    )
 
 
 class NoDualsError(PyomoException):
-    def __init__(self):
-        super().__init__(
-            'Solver does not currently have valid duals. Please '
-            'check results.termination_condition and/or results.solution_status.'
-        )
+    default_message = (
+        'Solver does not currently have valid duals. Please '
+        'check results.termination_condition and/or results.solution_status.'
+    )
 
 
 class NoReducedCostsError(PyomoException):
-    def __init__(self):
-        super().__init__(
-            'Solver does not currently have valid reduced costs. Please '
-            'check results.termination_condition and/or results.solution_status.'
-        )
+    default_message = (
+        'Solver does not currently have valid reduced costs. Please '
+        'check results.termination_condition and/or results.solution_status.'
+    )
 
 
 class IncompatibleModelError(PyomoException):
-    def __init__(self):
-        super().__init__(
-            'Model is not compatible with the chosen solver. Please check '
-            'the model and solver.'
-        )
+    default_message = (
+        'Model is not compatible with the chosen solver. Please check '
+        'the model and solver.'
+    )
 
 
 def get_objective(block):