Propagate underscores_to_dashes to subparsers

Author: swansonk14

tap/tap.py

@@ -1,6 +1,7 @@
 from argparse import ArgumentParser
 from collections import OrderedDict
 from copy import deepcopy
+from functools import partial
 import json
 from pprint import pformat
 import re
@@ -298,7 +299,7 @@ def _add_subparsers(self) -> None:
 
         # Load each subparser
         for flag, subparser_type, kwargs in self._subparser_buffer:
-            self._subparsers._parser_class = subparser_type
+            self._subparsers._parser_class = partial(subparser_type, underscores_to_dashes=self._underscores_to_dashes)
             self._subparsers.add_parser(flag, **kwargs)
 
     def add_subparsers(self, **kwargs) -> None:

tests/test_subparser.py

@@ -1,4 +1,5 @@
 import sys
+from typing import Union
 from typing_extensions import Literal
 import unittest
 from unittest import TestCase
@@ -195,6 +196,32 @@ def configure(self):
         with self.assertRaises(SystemExit):
             Args().parse_args('b a'.split())
 
+    def test_subparser_underscores_to_dashes(self):
+        class AddProposal(Tap):
+            proposal_id: int
+
+        class Arguments(Tap):
+            def configure(self) -> None:
+                self.add_subparsers(dest="subparser_name")
+
+                self.add_subparser(
+                    "add-proposal",
+                    AddProposal,
+                    help="Add a new proposal",
+                )
+
+        args_underscores: Union[Arguments, AddProposal] = Arguments(underscores_to_dashes=False).parse_args('add-proposal --proposal_id 1'.split())
+        self.assertEqual(args_underscores.proposal_id, 1)
+
+        args_dashes: Union[Arguments, AddProposal] = Arguments(underscores_to_dashes=True).parse_args('add-proposal --proposal-id 1'.split())
+        self.assertEqual(args_dashes.proposal_id, 1)
+
+        with self.assertRaises(SystemExit):
+            Arguments(underscores_to_dashes=False).parse_args('add-proposal --proposal-id 1'.split())
+
+        with self.assertRaises(SystemExit):
+            Arguments(underscores_to_dashes=True).parse_args('add-proposal --proposal_id 1'.split())
+
 
 if __name__ == '__main__':
     unittest.main()