Merge pull request #25 from explosion/feature/bool-negation

radicli/tests/test_cli.py

@@ -985,3 +985,26 @@ def test(a: str, b: str = "1", *, c: int = 1, d: bool = False, e: str = "yo"):
     args = ["hello", "--c", "1", "--d"]
     parsed = cli.parse(args, cli.commands["test"])
     assert parsed == {"a": "hello", "c": 1, "d": True}
+
+
+def test_cli_booleans():
+    cli = Radicli()
+
+    @cli.command(
+        "test",
+        a=Arg("--a"),
+        b=Arg("--b"),
+        c=Arg("--c"),
+    )
+    def test(a: bool, b: bool = False, c: bool = True):
+        ...
+
+    args = ["--a", "--b", "--c"]
+    parsed = cli.parse(args, cli.commands["test"])
+    assert parsed == {"a": True, "b": True, "c": True}
+    args = []
+    parsed = cli.parse(args, cli.commands["test"])
+    assert parsed == {"a": False, "b": False, "c": True}
+    args = ["--no-c"]
+    parsed = cli.parse(args, cli.commands["test"])
+    assert parsed == {"a": False, "b": False, "c": False}

radicli/util.py

@@ -117,6 +117,46 @@ def __init__(self, arg_id: str, message: str):
         super().__init__(self.message)
 
 
+# This is included with argparse in Python 3.9+ and above, but we're also
+# supporting 3.8 so the action is inlined here
+class BooleanOptionalAction(argparse.Action):
+    def __init__(
+        self,
+        option_strings,
+        dest,
+        default=None,
+        type=None,
+        choices=None,
+        required=False,
+        help=None,
+        metavar=None,
+    ):
+        _option_strings = []
+        for option_string in option_strings:
+            _option_strings.append(option_string)
+            if option_string.startswith("--"):
+                option_string = "--no-" + option_string[2:]
+                _option_strings.append(option_string)
+        super().__init__(
+            option_strings=_option_strings,
+            dest=dest,
+            nargs=0,
+            default=default,
+            type=type,
+            choices=choices,
+            required=required,
+            help=help,
+            metavar=metavar,
+        )
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        if option_string is not None and option_string in self.option_strings:
+            setattr(namespace, self.dest, not option_string.startswith("--no-"))
+
+    def format_usage(self) -> str:
+        return " | ".join(self.option_strings)
+
+
 @dataclass
 class Arg:
     """Field for defining the CLI argument in the decorator."""
@@ -306,10 +346,8 @@ def get_arg(
                 f"boolean arguments need to be flags, e.g. --{arg.id.replace('_', '-')}",
             )
         arg.type = None
-        if default is True:
-            raise InvalidArgumentError(arg.id, "boolean flags need to default to False")
-        arg.default = False
-        arg.action = "store_true"
+        arg.default = False if default is not True else True
+        arg.action = "store_true" if arg.default is False else BooleanOptionalAction
         return arg
     if inspect.isclass(param_type) and issubclass(param_type, Enum):
         arg.choices = list(param_type.__members__.keys())

setup.cfg

@@ -1,5 +1,5 @@
 [metadata]
-version = 0.0.21
+version = 0.0.22
 description = Radically lightweight command-line interfaces
 url = https://github.com/explosion/radicli
 author = Explosion