Support boolean flags

README.md

@@ -132,6 +132,23 @@ of `add_options_from` for more information. In the following some possibilities
 @add_options_from(display_data, custom={'symbol': {'default': '#'}})
 ```
 
+### Boolean flags
+
+Boolean flags are supported via the `bool` type hint. The default behavior is to create an on-/off-option
+as described in the [click docs](https://click.palletsprojects.com/en/7.x/options/#boolean-flags).
+If this is undesired, it can be customized by using the `names` keyword parameter of `add_options_from`:
+
+```python
+foo: bool = True
+# translates to
+click.option('--foo/--no-foo', default=True)
+
+# Use the following to create an on-/off-option:
+add_options_from(my_func, names={'foo': ['--foo']})
+# translates to
+click.option('--foo', is_flag=True, default=True)
+```
+
 ### Lists and tuples
 
 `click-inspect` also supports sequences as type hints (e.g. `list[int]` or `tuple[int, str]`).
@@ -166,6 +183,6 @@ Args:
 So `Union[int, str]` is equivalent to `int`.
 Unions are also supported as part of the docstring via `int or str`.
 
-## Docstring styles
+### Docstring styles
 
 `click-inspect` supports inspecting [reST-style](https://www.python.org/dev/peps/pep-0287/) docstrings, as well as [Google-](https://google.github.io/styleguide/pyguide.html#38-comments-and-docstrings) and [Numpy-style](https://numpydoc.readthedocs.io/en/latest/format.html) docstrings via [`sphinx.ext.napoleon`](https://github.com/sphinx-doc/sphinx/tree/master/sphinx/ext/napoleon).

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "click-inspect"
-version = "0.2"
+version = "0.3"
 description = "Add options to click commands based on inspecting functions"
 authors = ["Dominik1123"]
 license = "MIT"

src/click_inspect/decorators.py

@@ -84,11 +84,6 @@ def _decorator(f):
             if not condition:
                 continue
 
-            try:
-                opt_names = names[name]
-            except KeyError:
-                opt_names = f'--{name.replace("_", "-")}',
-
             kwargs = {}
             if 'help' in p_doc[name]:
                 kwargs['help'] = p_doc[name]['help']
@@ -97,20 +92,33 @@ def _decorator(f):
                 kwargs['default'] = parameter.default
             else:
                 kwargs['required'] = True
+
+            try:
+                kwargs['type'] = custom[name]['type']
+            except KeyError:
                 try:
-                    kwargs['type'] = custom[name]['type']
+                    tp_hint = type_hints[name]
                 except KeyError:
                     try:
-                        tp_hint = type_hints[name]
+                        tp_hint = p_doc[name]['type']
                     except KeyError:
-                        try:
-                            tp_hint = p_doc[name]['type']
-                        except KeyError:
-                            tp_hint = None
+                        tp_hint = None
+                        if parameter.default is EMPTY:
                             warnings.warn(f'No type hint for parameter {name!r}')
-                    if tp_hint is not None:
-                        kwargs.update(_parse_type_hint_into_kwargs(tp_hint))
+                if tp_hint is not None:
+                    kwargs.update(_parse_type_hint_into_kwargs(tp_hint))
+
             kwargs.update(custom.get(name, {}))
+
+            try:
+                opt_names = names[name]
+            except KeyError:
+                opt_name = name.replace("_", "-")
+                if kwargs.get('is_flag', False):
+                    opt_names = [f'--{opt_name}/--no-{opt_name}']
+                else:
+                    opt_names = [f'--{opt_name}']
+
             click.option(*opt_names, **kwargs)(f)
         return f
 
@@ -119,7 +127,9 @@ def _decorator(f):
 
 def _parse_type_hint_into_kwargs(tp_hint):
     args, origin = get_args(tp_hint), get_origin(tp_hint)
-    if origin in (list, collections.abc.Sequence):
+    if tp_hint is bool:
+        return dict(is_flag=True)
+    elif origin in (list, collections.abc.Sequence):
         return dict(multiple=True, type=args[0])
     elif origin is tuple:
         return dict(type=args)

tests/conftest.py

@@ -5,7 +5,7 @@
 
 @pytest.fixture(scope='function')
 def base_function():
-    def _f(a, b: int = 1, *, c: int, d: str = 'test'):
+    def _f(a, b: int = 1, *, c: int, d: str = 'test', e: bool = True):
         """Short description.
 
         Long
@@ -16,6 +16,7 @@ def _f(a, b: int = 1, *, c: int, d: str = 'test'):
             b (int): This one should be added.
             c (int): This one should be added too.
             d (str): And so should this one.
+            e (bool): Boolean flag.
 
         Returns:
             str: This is just a test.

tests/test_decorators.py

@@ -13,28 +13,40 @@ def test_add_options_from(base_function):
     @add_options_from(base_function)
     def test(): pass
 
-    assert len(test.params) == 3
+    assert len(test.params) == 4
 
     assert test.params[0].name == 'b'
     assert test.params[0].opts == ['--b']
+    assert test.params[0].secondary_opts == []
     assert test.params[0].type is click.INT
     assert test.params[0].default == 1
     assert test.params[0].required is False
     assert test.params[0].help == 'This one should be added.'
 
     assert test.params[1].name == 'c'
     assert test.params[1].opts == ['--c']
+    assert test.params[1].secondary_opts == []
     assert test.params[1].type is click.INT
     assert test.params[1].required is True
     assert test.params[1].help == 'This one should be added too.'
 
     assert test.params[2].name == 'd'
     assert test.params[2].opts == ['--d']
+    assert test.params[2].secondary_opts == []
     assert test.params[2].type is click.STRING
     assert test.params[2].default == 'test'
     assert test.params[2].required is False
     assert test.params[2].help == 'And so should this one.'
 
+    assert test.params[3].name == 'e'
+    assert test.params[3].opts == ['--e']
+    assert test.params[3].secondary_opts == ['--no-e']
+    assert test.params[3].type is click.BOOL
+    assert test.params[3].is_flag is True
+    assert test.params[3].default is True
+    assert test.params[3].required is False
+    assert test.params[3].help == 'Boolean flag.'
+
 
 def test_add_options_from_infer_types_from_docstring(base_function):
     base_function.__annotations__ = {}
@@ -50,12 +62,14 @@ def test(): pass
 
     assert test.params[0].name == 'a'
     assert test.params[0].opts == ['--a']
+    assert test.params[0].secondary_opts == []
     assert test.params[0].type is click.STRING
     assert test.params[0].required is True
     assert test.params[0].help == 'This parameter should be skipped.'
 
     assert test.params[1].name == 'b'
     assert test.params[1].opts == ['--b']
+    assert test.params[1].secondary_opts == []
     assert test.params[1].type is click.INT
     assert test.params[1].default == 1
     assert test.params[1].required is False
@@ -67,42 +81,75 @@ def test_add_options_from_exclude(base_function):
     @add_options_from(base_function, exclude={'b', 'c'})
     def test(): pass
 
-    assert len(test.params) == 1
+    assert len(test.params) == 2
 
     assert test.params[0].name == 'd'
     assert test.params[0].opts == ['--d']
+    assert test.params[0].secondary_opts == []
     assert test.params[0].type is click.STRING
     assert test.params[0].default == 'test'
     assert test.params[0].required is False
     assert test.params[0].help == 'And so should this one.'
 
+    assert test.params[1].name == 'e'
+    assert test.params[1].opts == ['--e']
+    assert test.params[1].secondary_opts == ['--no-e']
+    assert test.params[1].type is click.BOOL
+    assert test.params[1].is_flag is True
+    assert test.params[1].default is True
+    assert test.params[1].required is False
+    assert test.params[1].help == 'Boolean flag.'
+
 
 def test_add_options_from_names(base_function):
     @click.command()
     @add_options_from(base_function, names={'b': ['-b'], 'd': ['-test', '--d']})
     def test(): pass
 
-    assert len(test.params) == 3
+    assert len(test.params) == 4
 
     assert test.params[0].name == 'b'
     assert test.params[0].opts == ['-b']
+    assert test.params[0].secondary_opts == []
 
     assert test.params[1].name == 'c'
     assert test.params[1].opts == ['--c']
+    assert test.params[1].secondary_opts == []
 
     assert test.params[2].name == 'd'
     assert test.params[2].opts == ['-test', '--d']
+    assert test.params[2].secondary_opts == []
+
+    assert test.params[3].name == 'e'
+    assert test.params[3].opts == ['--e']
+    assert test.params[3].secondary_opts == ['--no-e']
 
 
 def test_add_options_from_custom(base_function):
     @click.command()
     @add_options_from(base_function, custom={'d': dict(default='custom_default')})
     def test(): pass
 
-    assert len(test.params) == 3
+    assert len(test.params) == 4
     assert test.params[2].default == 'custom_default'
 
 
+def test_add_options_from_single_switch_boolean_flag(base_function):
+    @click.command()
+    @add_options_from(base_function, names={'e': ['--e']})
+    def test(): pass
+
+    assert len(test.params) == 4
+    assert test.params[3].name == 'e'
+    assert test.params[3].opts == ['--e']
+    assert test.params[3].secondary_opts == []
+    assert test.params[3].type is click.BOOL
+    assert test.params[3].is_flag is True
+    assert test.params[3].default is True
+    assert test.params[3].required is False
+    assert test.params[3].help == 'Boolean flag.'
+
+
 def test_add_options_from_warn_if_no_type():
     def func(*, a):
         """Test func.
@@ -119,6 +166,23 @@ def test(): pass
     assert str(warninfo[0].message.args[0]) == "No type hint for parameter 'a'"
 
 
+def test_add_options_from_no_warn_if_no_type_but_default():
+    def func(*, a = 1):
+        """Test func.
+
+        Args:
+            a: Test parameter
+        """
+
+    @click.command()
+    @add_options_from(func)
+    def test(): pass
+
+    assert len(test.params) == 1
+    assert test.params[0].type is click.INT
+    assert test.params[0].default == 1
+
+
 def test_add_options_from_unsupported_docstring_style():
     def func(*, a: int):
         """Test func.

tests/test_parser.py

@@ -134,6 +134,7 @@ def test_parse_docstring_base_function(base_function):
         'b': {'help': 'This one should be added.', 'type': int},
         'c': {'help': 'This one should be added too.', 'type': int},
         'd': {'help': 'And so should this one.', 'type': str},
+        'e': {'help': 'Boolean flag.', 'type': bool},
     }