Improve data import for PartParameterTemplate (#6182)

- Create Resource class which uses InvenTreeResource base
- Ensure 'units' field is converted to string if empty
- Handle null choices field in PartParameterTemplate model

InvenTree/InvenTree/admin.py

@@ -19,6 +19,9 @@ class InvenTreeResource(ModelResource):
     MAX_IMPORT_ROWS = 1000
     MAX_IMPORT_COLS = 100
 
+    # List of fields which should be converted to empty strings if they are null
+    CONVERT_NULL_FIELDS = []
+
     def import_data_inner(
         self,
         dataset,
@@ -79,6 +82,13 @@ class InvenTreeResource(ModelResource):
 
         return [f for f in fields if f.column_name not in fields_to_exclude]
 
+    def before_import_row(self, row, row_number=None, **kwargs):
+        """Run custom code before importing each row"""
+
+        for field in self.CONVERT_NULL_FIELDS:
+            if field in row and row[field] is None:
+                row[field] = ''
+
 
 class CustomRateAdmin(RateAdmin):
     """Admin interface for the Rate class"""

InvenTree/part/admin.py

@@ -356,9 +356,32 @@ class BomItemAdmin(ImportExportModelAdmin):
     autocomplete_fields = ('part', 'sub_part',)
 
 
+class ParameterTemplateResource(InvenTreeResource):
+    """Class for managing ParameterTemplate import/export"""
+
+    # The following fields will be converted from None to ''
+    CONVERT_NULL_FIELDS = [
+        'choices',
+        'units'
+    ]
+
+    class Meta:
+        """Metaclass definition"""
+        model = models.PartParameterTemplate
+        skip_unchanged = True
+        report_skipped = False
+        clean_model_instances = True
+
+        exclude = [
+            'metadata',
+        ]
+
+
 class ParameterTemplateAdmin(ImportExportModelAdmin):
     """Admin class for the PartParameterTemplate model"""
 
+    resource_class = ParameterTemplateResource
+
     list_display = ('name', 'units')
 
     search_fields = ('name', 'units')

InvenTree/part/models.py

@@ -3346,7 +3346,10 @@ class PartParameterTemplate(MetadataMixin, models.Model):
                 })
 
         # Check that 'choices' are in fact valid
-        self.choices = self.choices.strip()
+        if self.choices is None:
+            self.choices = ''
+        else:
+            self.choices = str(self.choices).strip()
 
         if self.choices:
             choice_set = set()