updating 'rotconsts' ref to be compatible with cclib v1.8+

environment.yml

@@ -16,6 +16,7 @@
 #   made dependency list more explicit (@JacksonBurns).
 # - October 16, 2023 Switched RDKit and descripatastorus to conda-forge,
 #   moved diffeqpy to pip and (temporarily) removed chemprop
+# - April 17, 2024 Limit versions of cclib at advice of maintainers.
 #
 name: rmg_env
 channels:
@@ -44,7 +45,8 @@ dependencies:
   - coolprop
   - cantera::cantera=2.6
   - conda-forge::mopac
-  - conda-forge::cclib >=1.6.3,<1.8.0
+  # see https://github.com/ReactionMechanismGenerator/RMG-Py/pull/2639#issuecomment-2050292972
+  - conda-forge::cclib >=1.6.3,<2
   - conda-forge::openbabel >= 3
   - conda-forge::rdkit >=2022.09.1
 

rmgpy/qm/molecule.py

@@ -408,19 +408,28 @@ def parse(self):
         parser = self.get_parser(self.output_file_path)
         parser.logger.setLevel(
             logging.ERROR
-        )  # cf. http://cclib.sourceforge.net/wiki/index.php/Using_cclib#Additional_information
-        parser.rotcons = (
+        )  # cf. https://cclib.github.io/index.html#how-to-use-cclib
+        parser.molmass = None # give it an attribute and it won't delete it, leaving it on the parser object
+        parser.rotcons = (  # for cclib < 1.8.0
             []
-        )  # give it an attribute and it won't delete it, leaving it on the parser object
-        parser.molmass = None  # give it an attribute and it won't delete it, leaving it on the parser object
-        cclib_data = parser.parse()
+        )
+        parser.rotconsts = (  # for cclib >= 1.8.0
+            []
+        )
+        cclib_data = parser.parse()  # fills in either parser.rotcons or parser.rotconsts but not both
+        assert bool(parser.rotconsts) != bool(parser.rotcons)
+        if parser.rotcons:  # for cclib < 1.8.0
+            cclib_data.rotcons = (
+                parser.rotcons
+            )
+        else:  # for cclib >= 1.8.0
+            cclib_data.rotconsts = (
+                parser.rotconsts
+            )
         radical_number = self.molecule.get_radical_count()
-        cclib_data.rotcons = (
-            parser.rotcons
-        )  # this hack required because rotcons not part of a default cclib data object
         cclib_data.molmass = (
             parser.molmass
-        )  # this hack required because rotcons not part of a default cclib data object
+        )  # this hack required because molmass is not part of a default cclib data object
         qm_data = parse_cclib_data(
             cclib_data, radical_number + 1
         )  # Should `radical_number+1` be `self.molecule.multiplicity` in the next line of code? It's the electronic ground state degeneracy.

rmgpy/qm/qmdata.py

@@ -98,7 +98,11 @@ def parse_cclib_data(cclib_data, ground_state_degeneracy):
             molecular_mass = None
         energy = (cclib_data.scfenergies[-1], 'eV/molecule')
         atomic_numbers = cclib_data.atomnos
-        rotational_constants = (cclib_data.rotcons[-1], 'cm^-1')
+        if hasattr(cclib_data, 'rotconsts'):
+            rotational_constants = (cclib_data.rotconsts[-1], 'cm^-1')
+        else:
+            rotational_constants = (cclib_data.rotcons[-1], 'cm^-1')
+
         atom_coords = (cclib_data.atomcoords[-1], 'angstrom')
         frequencies = (cclib_data.vibfreqs, 'cm^-1')