TriFlag improvements related to defaults

Makefile

@@ -18,3 +18,6 @@ publish:
 
 sign:
 	for f in dist/*; do echo "Signing $${f}"; gpg --armor --detach-sign $${f}; done
+
+verify:
+	for f in dist/*.asc; do gpg --verify $$f $${f%.asc}; done

docs/_src/parameters.rst

@@ -270,7 +270,12 @@ provided, respectively.
 :alt_long: The alternate long form to use.
 :alt_short: The alternate short form to use.
 :alt_help: The help text to display with the alternate option strings.
-:default: The default value to use if neither the primary or alternate options are provided.  Defaults to None.
+:default: The default value to use if neither the primary nor alternate options are provided.  Defaults to None.
+
+    .. version-changed:: 2026-06-30
+
+        The ``default`` value may now match either value in ``consts`` (previously, matching values were rejected).
+
 :name_mode: Override the configured :ref:`configuration:Parsing Options:option_name_mode` for the TriFlag.
 :type: A callable (function, class, etc.) that accepts a single string argument and returns a boolean value, which
   should be called on environment variable values, if any are configured for this TriFlag via

lib/cli_command_parser/parameters/base.py

@@ -380,16 +380,16 @@ def register_default_cb(self, method: CommandMethod[D]) -> CommandMethod[D]:
         :return: The method, unchanged.
         """
         if self.default is not _NotSet:
-            problem = f'default={self.default!r}'
+            problem = f'already has default={self.default!r}'
         elif self.default_cb:
-            problem = f'default_cb={self.default_cb!r}'
+            problem = f'already has default_cb={self.default_cb!r}'
+        elif self.required:
+            problem = 'has required=True'
         else:
             problem = None
 
         if problem:
-            raise ParameterDefinitionError(
-                f'Cannot register a default callback method for {self} because it already has {problem}'
-            )
+            raise ParameterDefinitionError(f'Cannot register a default callback method for {self} because it {problem}')
 
         self.default_cb = DefaultCallback(method, True)
         return method

lib/cli_command_parser/parameters/options.py

@@ -436,7 +436,7 @@ class TriFlag(BaseFlag[B, D], actions=(StoreConst, AppendConst)):
     :param alt_short: The alternate short form to use.
     :param alt_help: The help text to display with the alternate option strings.
     :param action: The action to take on individual parsed values.  Only ``store_const`` (the default) is supported.
-    :param default: The default value to use if neither the primary or alternate options are provided.  Defaults
+    :param default: The default value to use if neither the primary nor alternate options are provided.  Defaults
       to None.
     :param name_mode: Override the configured :ref:`configuration:Parsing Options:option_name_mode` for this TriFlag.
     :param type: A callable (function, class, etc.) that accepts a single string argument and returns a boolean value,
@@ -495,16 +495,13 @@ def __init__(
             raise ParameterDefinitionError(msg) from e
 
         if default is _NotSet and default_cb is None:
-            if not kwargs.get('required', False):
+            if kwargs.get('required', False):
+                self._default_cb_ok = False  # prevent late registration of a default callback when param is required
+            else:
                 default = None  # type: ignore[assignment]
         else:
             self._default_cb_ok = False
 
-        if default in consts:
-            raise ParameterDefinitionError(
-                f'Invalid {default=} with {consts=} - the default must not match either value'
-            )
-
         alt_opt_strs = (opt for opt in (alt_short, alt_long) if opt)
         super().__init__(*option_strs, *alt_opt_strs, action=action, default=default, default_cb=default_cb, **kwargs)
         self.consts = consts

tests/test_parameters/test_flags.py

@@ -76,19 +76,19 @@ class Foo(Command):
 
     def test_nargs_not_allowed(self):
         with self.assertRaises(TypeError):
-            Flag(nargs='+')
+            Flag(nargs='+')  # type: ignore
 
     def test_choices_not_allowed(self):
         with self.assertRaises(TypeError):
-            Flag(choices=(1, 2))
+            Flag(choices=(1, 2))  # type: ignore
 
     def test_allow_leading_dash_not_allowed(self):
         with self.assertRaises(TypeError):
-            Flag(allow_leading_dash=True)
+            Flag(allow_leading_dash=True)  # type: ignore
 
     def test_default_cb_rejected(self):
         with self.assert_raises_contains_str(ParameterDefinitionError, "The 'default_cb' arg is not supported"):
-            Flag(default_cb=lambda: 123)
+            Flag(default_cb=lambda: 123)  # type: ignore
 
     # endregion
 
@@ -229,15 +229,7 @@ def test_bad_consts(self):
         fail_cases = [({'consts': None}, exc), ({'consts': (1,)}, exc), ({'consts': [1, 2, 3]}, exc)]
         self.assert_call_fails_cases(TriFlag, fail_cases)
 
-    def test_default_in_consts_rejected(self):
-        expected = 'the default must not match either value'
-        cases = [((None, 'foo'), None), (('foo', None), None), ((True, False), True), ((True, False), False)]
-        for consts, default in cases:
-            with self.subTest(consts=consts, default=default):
-                with self.assert_raises_contains_str(ParameterDefinitionError, expected):
-                    TriFlag(consts=consts, default=default)
-
-    def test_register_default_cb_rejected(self):
+    def test_register_default_cb_rejected_due_to_existing_default(self):
         with self.assert_raises_contains_str(ParameterDefinitionError, 'because it already has default='):
 
             class Foo(Command):
@@ -247,6 +239,16 @@ class Foo(Command):
                 def baz(self):
                     pass
 
+    def test_register_default_cb_rejected_due_to_required(self):
+        with self.assert_raises_contains_str(ParameterDefinitionError, 'because it has required=True'):
+
+            class Foo(Command):
+                bar = TriFlag(required=True)
+
+                @bar.register_default_cb
+                def baz(self):
+                    pass
+
     # region Option Strings
 
     def test_bad_alt_short(self):

tests/test_parsing/test_parse_flags.py

@@ -437,6 +437,20 @@ def _bar(self):
         ]
         self.assert_parse_results_cases(Cmd, success_cases)
 
+    def test_default_matching_const(self):
+        class Cmd(Command):
+            foo = TriFlag(default=False)
+            bar = TriFlag(consts=(False, True), default=True)
+
+        success_cases = [
+            ([], {'foo': False, 'bar': True}),
+            (['--foo'], {'foo': True, 'bar': True}),
+            (['--bar'], {'foo': False, 'bar': False}),
+            (['--no-foo'], {'foo': False, 'bar': True}),
+            (['--no-bar'], {'foo': False, 'bar': True}),
+        ]
+        self.assert_parse_results_cases(Cmd, success_cases)
+
     # region Env Var Handling
 
     def test_env_var(self):