Refactoring for constance cli command

constance/management/commands/constance.py

@@ -1,4 +1,3 @@
-from django import VERSION
 from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.core.management import BaseCommand
@@ -30,67 +29,56 @@
 class Command(BaseCommand):
     help = _('Get/Set In-database config settings handled by Constance')
 
+    GET = 'get'
+    SET = 'set'
+    LIST = 'list'
+    REMOVE_STALE_KEYS = 'remove_stale_keys'
+
     def add_arguments(self, parser):
         subparsers = parser.add_subparsers(dest='command')
-        # API changed in Django>=2.1. cmd argument was removed.
-        parser_list = self._subparsers_add_parser(
-            subparsers, 'list', cmd=self, help='list all Constance keys and their values'
-        )
+        subparsers.add_parser(self.LIST, help='list all Constance keys and their values')
 
-        parser_get = self._subparsers_add_parser(subparsers, 'get', cmd=self, help='get the value of a Constance key')
+        parser_get = subparsers.add_parser(self.GET, help='get the value of a Constance key')
         parser_get.add_argument('key', help='name of the key to get', metavar='KEY')
 
-        parser_set = self._subparsers_add_parser(subparsers, 'set', cmd=self, help='set the value of a Constance key')
-        parser_set.add_argument('key', help='name of the key to get', metavar='KEY')
+        parser_set = subparsers.add_parser(self.SET, help='set the value of a Constance key')
+        parser_set.add_argument('key', help='name of the key to set', metavar='KEY')
         # use nargs='+' so that we pass a list to MultiValueField (eg SplitDateTimeField)
         parser_set.add_argument('value', help='value to set', metavar='VALUE', nargs='+')
 
-        self._subparsers_add_parser(
-            subparsers,
-            'remove_stale_keys',
-            cmd=self,
+        subparsers.add_parser(
+            self.REMOVE_STALE_KEYS,
             help='delete all Constance keys and their values if they are not in settings.CONSTANCE_CONFIG (stale keys)',
         )
 
-    def _subparsers_add_parser(self, subparsers, name, **kwargs):
-        # API in Django >= 2.1 changed and removed cmd parameter from add_parser
-        if VERSION >= (2, 1) and 'cmd' in kwargs:
-            kwargs.pop('cmd')
-        return subparsers.add_parser(name, **kwargs)
-
     def handle(self, command, key=None, value=None, *args, **options):
-        if command == 'get':
+        if command == self.GET:
             try:
                 self.stdout.write(str(getattr(config, key)), ending='\n')
-            except AttributeError as e:
-                raise CommandError(key + ' is not defined in settings.CONSTANCE_CONFIG')
-
-        elif command == 'set':
+            except AttributeError:
+                raise CommandError(f'{key} is not defined in settings.CONSTANCE_CONFIG')
+        elif command == self.SET:
             try:
                 if len(value) == 1:
                     # assume that if a single argument was passed, the field doesn't expect a list
                     value = value[0]
-
                 _set_constance_value(key, value)
-            except KeyError as e:
-                raise CommandError(key + ' is not defined in settings.CONSTANCE_CONFIG')
+            except KeyError:
+                raise CommandError(f'{key} is not defined in settings.CONSTANCE_CONFIG')
             except ValidationError as e:
                 raise CommandError(', '.join(e))
-
-        elif command == 'list':
+        elif command == self.LIST:
             for k, v in get_values().items():
                 self.stdout.write(f'{k}\t{v}', ending='\n')
-
-        elif command == 'remove_stale_keys':
+        elif command == self.REMOVE_STALE_KEYS:
             actual_keys = settings.CONSTANCE_CONFIG.keys()
-
             stale_records = Constance.objects.exclude(key__in=actual_keys)
             if stale_records:
                 self.stdout.write('The following record will be deleted:', ending='\n')
             else:
-                self.stdout.write('There are no stale records in database.', ending='\n')
-
+                self.stdout.write('There are no stale records in the database.', ending='\n')
             for stale_record in stale_records:
                 self.stdout.write(f'{stale_record.key}\t{stale_record.value}', ending='\n')
-
             stale_records.delete()
+        else:
+            raise CommandError('Invalid command')