Fix #8103: autodoc: cached_property is not considered as a property

sphinx.util.inspect:isproperty() does not considers that
cached_property decorator that has been added since Python 3.8 is
a kind of properties.  This fixes it.

CHANGES

@@ -16,6 +16,7 @@ Features added
 Bugs fixed
 ----------
 
+* #8103: autodoc: functools.cached_property is not considered as a property
 * #8093: The highlight warning has wrong location in some builders (LaTeX,
   singlehtml and so on)
 

sphinx/util/inspect.py

@@ -304,6 +304,11 @@ def iscoroutinefunction(obj: Any) -> bool:
 
 def isproperty(obj: Any) -> bool:
     """Check if the object is property."""
+    if sys.version_info > (3, 8):
+        from functools import cached_property  # cached_property is available since py3.8
+        if isinstance(obj, cached_property):
+            return True
+
     return isinstance(obj, property)
 
 

tests/roots/test-ext-autodoc/target/cached_property.py

@@ -0,0 +1,7 @@
+from functools import cached_property
+
+
+class Foo:
+    @cached_property
+    def prop(self) -> int:
+        return 1

tests/test_ext_autodoc.py

@@ -881,6 +881,26 @@ def test_autodoc_descriptor(app):
     ]
 
 
+@pytest.mark.skipif(sys.version_info < (3, 8),
+                    reason='cached_property is available since python3.8.')
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_autodoc_cached_property(app):
+    options = {"members": None,
+               "undoc-members": True}
+    actual = do_autodoc(app, 'class', 'target.cached_property.Foo', options)
+    assert list(actual) == [
+        '',
+        '.. py:class:: Foo()',
+        '   :module: target.cached_property',
+        '',
+        '',
+        '   .. py:method:: Foo.prop',
+        '      :module: target.cached_property',
+        '      :property:',
+        '',
+    ]
+
+
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_autodoc_member_order(app):
     # case member-order='bysource'