fix: positionals cannot have action=store_{true,false}

src/argh/assembling.py

@@ -221,6 +221,7 @@ def guess_extra_parser_add_argument_spec_kwargs(
     # TODO: use typing to extract
     other_add_parser_kwargs = parser_add_argument_spec.other_add_parser_kwargs
     guessed: Dict[str, Any] = {}
+    is_positional = not parser_add_argument_spec.cli_arg_names[0].startswith("-")
 
     # Parser actions that accept argument 'type'
     TYPE_AWARE_ACTIONS = "store", "append"
@@ -229,8 +230,9 @@ def guess_extra_parser_add_argument_spec_kwargs(
     default_value = parser_add_argument_spec.default_value
     if default_value not in (None, NotDefined):
         if isinstance(default_value, bool):
-            if other_add_parser_kwargs.get("action") is None:
+            if not is_positional and other_add_parser_kwargs.get("action") is None:
                 # infer action from default value
+                # (not applicable to positionals: _StoreAction doesn't accept `nargs`)
                 guessed["action"] = "store_false" if default_value else "store_true"
         elif other_add_parser_kwargs.get("type") is None:
             # infer type from default value

tests/test_assembling.py

@@ -52,13 +52,21 @@ def test_guess_type_from_default():
 
 
 def test_guess_action_from_default():
-    # True → store_false
+    # positional, default True → ignore
     given = ParserAddArgumentSpec("foo", ["foo"], default_value=False)
+    assert {} == argh.assembling.guess_extra_parser_add_argument_spec_kwargs(given)
+
+    # named, default True → store_false
+    given = ParserAddArgumentSpec("foo", ["--foo"], default_value=False)
     guessed = {"action": "store_true"}
     assert guessed == argh.assembling.guess_extra_parser_add_argument_spec_kwargs(given)
 
-    # True → store_false
+    # positional, default False → ignore
     given = ParserAddArgumentSpec("foo", ["foo"], default_value=True)
+    assert {} == argh.assembling.guess_extra_parser_add_argument_spec_kwargs(given)
+
+    # named, True → store_false
+    given = ParserAddArgumentSpec("foo", ["--foo"], default_value=True)
     guessed = {"action": "store_false"}
     assert guessed == argh.assembling.guess_extra_parser_add_argument_spec_kwargs(given)
 
@@ -75,6 +83,26 @@ def test_guess_action_from_default():
     assert guessed == argh.assembling.guess_extra_parser_add_argument_spec_kwargs(given)
 
 
+def test_positional_with_default_int():
+    def func(pos_int_default=123):
+        ...
+
+    parser = argh.ArghParser()
+    parser.set_default_command(func)
+    assert parser.format_usage() == "usage: pytest [-h] [pos-int-default]\n"
+    assert "pos-int-default  123" in parser.format_help()
+
+
+def test_positional_with_default_bool():
+    def func(pos_bool_default=False):
+        ...
+
+    parser = argh.ArghParser()
+    parser.set_default_command(func)
+    assert parser.format_usage() == "usage: pytest [-h] [pos-bool-default]\n"
+    assert "pos-bool-default  False" in parser.format_help()
+
+
 def test_set_default_command():
     def func(**kwargs):
         pass