XspectraCrystalWorkChain: Correct Error Handling

Changes requested for PR #1028 (2)

Corrects error handling behaviour for `validate_inputs` to use `return`
rather than `raise`.

Also fixes minor formatting errors in `symmetry_data` `help` entry and
removes unnecessary uses of `+`.

src/aiida_quantumespresso/workflows/xspectra/crystal.py

@@ -4,7 +4,7 @@
 Uses QuantumESPRESSO pw.x and xspectra.x.
 """
 from aiida import orm
-from aiida.common import AttributeDict, ValidationError
+from aiida.common import AttributeDict
 from aiida.engine import ToContext, WorkChain, if_
 from aiida.orm import UpfData as aiida_core_upf
 from aiida.plugins import CalculationFactory, DataFactory, WorkflowFactory
@@ -180,10 +180,10 @@ def define(cls, spec):
             required=False,
             help=(
                 'Input namespace to define equivalent sites and spacegroup number for the system. If defined, will '
-                + 'skip symmetry analysis and structure standardization. Use *only* if symmetry data are known'
-                + 'for certain. Requires ``spacegroup_number`` (Int) and ``equivalent_sites_data`` (Dict) to be'
-                + 'defined separately. All keys in `equivalent_sites_data` must be formatted as "site_<site_index>".'
-                + 'See docstring of `get_xspectra_structures` for more information about inputs.'
+                'skip symmetry analysis and structure standardization. Use *only* if symmetry data are known '
+                'for certain. Requires ``spacegroup_number`` (Int) and ``equivalent_sites_data`` (Dict) to be '
+                'defined separately. All keys in `equivalent_sites_data` must be formatted as "site_<site_index>". '
+                'See docstring of `get_xspectra_structures` for more information about inputs.'
             )
         )
         spec.inputs.validator = cls.validate_inputs
@@ -382,9 +382,8 @@ def get_builder_from_protocol( # pylint: disable=too-many-statements
         return builder
 
 
-    # pylint: disable=too-many-statements
     @staticmethod
-    def validate_inputs(inputs, _):
+    def validate_inputs(inputs, _): # pylint: disable=too-many-return-statements
         """Validate the inputs before launching the WorkChain."""
         structure = inputs['structure']
         kinds_present = [kind.name for kind in structure.kinds]
@@ -396,58 +395,57 @@ def validate_inputs(inputs, _):
             if element not in elements_present:
                 extra_elements.append(element)
         if len(extra_elements) > 0:
-            raise ValidationError(
+            return (
                 f'Some elements in ``elements_list`` {extra_elements} do not exist in the'
                 f' structure provided {elements_present}.'
             )
 
         abs_atom_marker = inputs['abs_atom_marker'].value
         if abs_atom_marker in kinds_present:
-            raise ValidationError(
+            return (
                 f'The marker given for the absorbing atom ("{abs_atom_marker}") matches an existing Kind in the '
                 f'input structure ({kinds_present}).'
             )
 
         if not inputs['core']['get_powder_spectrum'].value:
-            raise ValidationError(
+            return (
                 'The ``get_powder_spectrum`` input for the XspectraCoreWorkChain namespace must be ``True``.'
             )
 
         if 'upf2plotcore_code' not in inputs and 'core_wfc_data' not in inputs:
-            raise ValidationError(
+            return (
                 'Neither a ``Code`` node for upf2plotcore.sh or a set of ``core_wfc_data`` were provided.'
             )
 
         if 'core_wfc_data' in inputs:
             core_wfc_data_list = sorted(inputs['core_wfc_data'].keys())
             if core_wfc_data_list != absorbing_elements_list:
-                raise ValidationError(
+                return (
                     f'The ``core_wfc_data`` provided ({core_wfc_data_list}) does not match the list of'
                     f' absorbing elements ({absorbing_elements_list})'
                 )
-            else:
-                empty_core_wfc_data = []
-                for key, value in inputs['core_wfc_data'].items():
-                    header_line = value.get_content()[:40]
-                    try:
-                        num_core_states = int(header_line.split(' ')[5])
-                    except Exception as exc:
-                        raise ValidationError(
-                            'The core wavefunction data file is not of the correct format'
-                        ) from exc
-                    if num_core_states == 0:
-                        empty_core_wfc_data.append(key)
-                if len(empty_core_wfc_data) > 0:
-                    raise ValidationError(
-                        f'The ``core_wfc_data`` provided for elements {empty_core_wfc_data} do not contain '
-                        'any wavefunction data.'
-                    )
+            empty_core_wfc_data = []
+            for key, value in inputs['core_wfc_data'].items():
+                header_line = value.get_content()[:40]
+                try:
+                    num_core_states = int(header_line.split(' ')[5])
+                except: # pylint: disable=bare-except
+                    return (
+                        'The core wavefunction data file is not of the correct format'
+                    ) # pylint: enable=bare-except
+                if num_core_states == 0:
+                    empty_core_wfc_data.append(key)
+            if len(empty_core_wfc_data) > 0:
+                return (
+                    f'The ``core_wfc_data`` provided for elements {empty_core_wfc_data} do not contain '
+                    'any wavefunction data.'
+                )
 
         if 'symmetry_data' in inputs:
             spacegroup_number = inputs['symmetry_data']['spacegroup_number'].value
             equivalent_sites_data = inputs['symmetry_data']['equivalent_sites_data'].get_dict()
             if spacegroup_number <= 0 or spacegroup_number >= 231:
-                raise ValidationError(
+                return (
                     f'Input spacegroup number ({spacegroup_number}) outside of valid range (1-230).'
                 )
 
@@ -466,25 +464,23 @@ def validate_inputs(inputs, _):
                 elif value['symbol'] not in input_elements:
                     input_elements.append(value['symbol'])
                     if value['site_index'] < 0 or value['site_index'] >= len(structure.sites):
-                        raise ValidationError(
+                        return (
                             f'The site index for {site_label} ({value["site_index"]}) is outside the range of '
                             + f'sites within the structure (0-{len(structure.sites) -1}).'
                         )
 
             if len(invalid_entries) != 0:
-                raise ValidationError(
+                return (
                     f'The required keys ({required_keys}) were not found in the following entries: {invalid_entries}'
                 )
 
             sorted_input_elements = sorted(input_elements)
             if sorted_input_elements != absorbing_elements_list:
-                raise ValidationError(
-                    f'Elements defined for sites in `equivalent_sites_data` ({sorted_input_elements}) do not match the'
-                    + f' list of absorbing elements ({absorbing_elements_list})'
-                )
+                return (f'Elements defined for sites in `equivalent_sites_data` ({sorted_input_elements}) '
+                 f'do not match the list of absorbing elements ({absorbing_elements_list})')
 
 
-    # pylint: enable=too-many-statements
+    # pylint: enable=too-many-return-statements
     def setup(self):
         """Set required context variables."""
         if 'core_wfc_data' in self.inputs.keys():