Add sphinx.util.inspect:getslots() to get __slots__ attribute

sphinx/util/inspect.py

@@ -137,6 +137,27 @@ def unwrap_all(obj: Any, *, stop: Callable = None) -> Any:
             return obj
 
 
+def getslots(obj: Any) -> Optional[Dict]:
+    """Get __slots__ attribute of the class as dict.
+
+    Return None if gienv *obj* does not have __slots__.
+    """
+    if not inspect.isclass(obj):
+        raise TypeError
+
+    __slots__ = safe_getattr(obj, '__slots__', None)
+    if __slots__ is None:
+        return None
+    elif isinstance(__slots__, dict):
+        return __slots__
+    elif isinstance(__slots__, str):
+        return {__slots__: None}
+    elif isinstance(__slots__, (list, tuple)):
+        return {e: None for e in __slots__}
+    else:
+        raise ValueError
+
+
 def isenumclass(x: Any) -> bool:
     """Check if the object is subclass of enum."""
     return inspect.isclass(x) and issubclass(x, enum.Enum)

tests/test_util_inspect.py

@@ -493,6 +493,28 @@ def test_dict_customtype():
     assert "<CustomType(2)>: 2" in description
 
 
+def test_getslots():
+    class Foo:
+        pass
+
+    class Bar:
+        __slots__ = ['attr']
+
+    class Baz:
+        __slots__ = {'attr': 'docstring'}
+
+    class Qux:
+        __slots__ = 'attr'
+
+    assert inspect.getslots(Foo) is None
+    assert inspect.getslots(Bar) == {'attr': None}
+    assert inspect.getslots(Baz) == {'attr': 'docstring'}
+    assert inspect.getslots(Qux) == {'attr': None}
+
+    with pytest.raises(TypeError):
+        inspect.getslots(Bar())
+
+
 @pytest.mark.sphinx(testroot='ext-autodoc')
 def test_isclassmethod(app):
     from target.methods import Base, Inherited