fix: use a custom error to stop leatsq

Author: ycexiao

src/diffpy/morph/log.py

@@ -50,4 +50,13 @@ def set_verbosity(vb):
     return
 
 
+class MorphOptimizationError(Exception):
+    "Custom error for morph optimization process."
+
+    def __init__(self, value):
+        super().__init__(value)
+
+    pass
+
+
 # End of file

src/diffpy/morph/morphapp.py

@@ -27,6 +27,7 @@
 import diffpy.morph.refine as refine
 import diffpy.morph.tools as tools
 from diffpy.morph import __save_morph_as__
+from diffpy.morph.log import MorphOptimizationError
 from diffpy.morph.version import __version__
 
 
@@ -680,7 +681,7 @@ def single_morph(
                 refiner.refine(*rptemp)
             # Adjust all parameters
             refiner.refine(*refpars)
-        except ValueError as e:
+        except (ValueError, MorphOptimizationError) as e:
             parser.custom_error(str(e))
     # Smear is not being refined, but baselineslope needs to refined to apply
     # smear

src/diffpy/morph/refine.py

@@ -12,13 +12,14 @@
 # See LICENSE.txt for license information.
 #
 ##############################################################################
-"""refine -- Refine a morph or morph chain
-"""
+"""refine -- Refine a morph or morph chain"""
 
 from numpy import array, concatenate, dot, exp, ones_like
 from scipy.optimize import leastsq
 from scipy.stats import pearsonr
 
+from diffpy.morph.log import MorphOptimizationError
+
 # Map of scipy minimizer names to the method that uses them
 
 
@@ -84,7 +85,7 @@ def _residual(self, pvals):
         )
         rvec = _y_target - _y_morph
         if len(rvec) < len(pvals):
-            raise ValueError(
+            raise MorphOptimizationError(
                 f"\nNumber of parameters (currently {len(pvals)}) cannot "
                 "exceed the number of shared grid points "
                 f"(currently {len(rvec)}). "

tests/test_refine.py

@@ -6,6 +6,7 @@
 import numpy
 import pytest
 
+from diffpy.morph.log import MorphOptimizationError
 from diffpy.morph.morph_helpers.transformpdftordf import TransformXtalPDFtoRDF
 from diffpy.morph.morph_helpers.transformrdftopdf import TransformXtalRDFtoPDF
 from diffpy.morph.morphs.morphchain import MorphChain
@@ -202,11 +203,11 @@ def test_refine_grid_bad(self, user_filesystem):
             "shared grid points."
         )
         with pytest.raises(
-            ValueError,
+            MorphOptimizationError,
         ) as error:
             refiner.refine(*refpars)
-            actual_error_message = str(error.value)
-            assert actual_error_message == expected_error_message
+        actual_error_message = str(error.value)
+        assert actual_error_message == expected_error_message
 
         # call from command line
         import subprocess