Fixed #29295 -- Fixed management command crash when using subparsers.

Thanks Tim Graham for the fix.

django/core/management/__init__.py

@@ -311,7 +311,7 @@ class ManagementUtility:
         # Preprocess options to extract --settings and --pythonpath.
         # These options could affect the commands that are available, so they
         # must be processed early.
-        parser = CommandParser(None, usage="%(prog)s subcommand [options] [args]", add_help=False)
+        parser = CommandParser(usage='%(prog)s subcommand [options] [args]', add_help=False)
         parser.add_argument('--settings')
         parser.add_argument('--pythonpath')
         parser.add_argument('args', nargs='*')  # catch-all

django/core/management/base.py

@@ -42,19 +42,20 @@ class CommandParser(ArgumentParser):
     SystemExit in several occasions, as SystemExit is unacceptable when a
     command is called programmatically.
     """
-    def __init__(self, cmd, **kwargs):
-        self.cmd = cmd
+    def __init__(self, **kwargs):
+        self.missing_args_message = kwargs.pop('missing_args_message', None)
+        self.called_from_command_line = kwargs.pop('called_from_command_line', None)
         super().__init__(**kwargs)
 
     def parse_args(self, args=None, namespace=None):
         # Catch missing argument for a better error message
-        if (hasattr(self.cmd, 'missing_args_message') and
+        if (self.missing_args_message and
                 not (args or any(not arg.startswith('-') for arg in args))):
-            self.error(self.cmd.missing_args_message)
+            self.error(self.missing_args_message)
         return super().parse_args(args, namespace)
 
     def error(self, message):
-        if self.cmd._called_from_command_line:
+        if self.called_from_command_line:
             super().error(message)
         else:
             raise CommandError("Error: %s" % message)
@@ -225,8 +226,10 @@ class BaseCommand:
         parse the arguments to this command.
         """
         parser = CommandParser(
-            self, prog="%s %s" % (os.path.basename(prog_name), subcommand),
+            prog='%s %s' % (os.path.basename(prog_name), subcommand),
             description=self.help or None,
+            missing_args_message=getattr(self, 'missing_args_message', None),
+            called_from_command_line=getattr(self, '_called_from_command_line', None),
         )
         # Add command-specific arguments first so that they appear in the
         # --help output before arguments common to all commands.

tests/user_commands/management/commands/subparser.py

@@ -0,0 +1,12 @@
+from django.core.management.base import BaseCommand
+
+
+class Command(BaseCommand):
+
+    def add_arguments(self, parser):
+        subparsers = parser.add_subparsers()
+        parser_foo = subparsers.add_parser('foo')
+        parser_foo.add_argument('bar', type=int)
+
+    def handle(self, *args, **options):
+        self.stdout.write(','.join(options))

tests/user_commands/tests.py

@@ -206,6 +206,16 @@ class CommandTests(SimpleTestCase):
         self.assertIn('need_me', out.getvalue())
         self.assertIn('needme2', out.getvalue())
 
+    def test_subparser(self):
+        out = StringIO()
+        management.call_command('subparser', 'foo', 12, stdout=out)
+        self.assertIn('bar', out.getvalue())
+
+    def test_subparser_invalid_option(self):
+        msg = "Error: invalid choice: 'test' (choose from 'foo')"
+        with self.assertRaisesMessage(CommandError, msg):
+            management.call_command('subparser', 'test', 12)
+
 
 class CommandRunTests(AdminScriptTestCase):
     """