Fix #9283: autodoc: failed to build doc for attribute not commented

Autoattribute directive should check the existence of instance attribute
that is defined inside __init__() but not having comments before
accessing it.

CHANGES

@@ -55,6 +55,8 @@ Bugs fixed
   undocumented
 * #9185: autodoc: typehints for overloaded functions and methods are inaccurate
 * #9250: autodoc: The inherited method not having docstring is wrongly parsed
+* #9283: autodoc: autoattribute directive failed to generate document for an
+  attribute not having any comment
 * #9270: html theme : pyramid theme generates incorrect logo links
 * #9217: manpage: The name of manpage directory that is generated by
   :confval:`man_make_section_directory` is not correct

sphinx/ext/autodoc/__init__.py

@@ -2356,9 +2356,29 @@ class RuntimeInstanceAttributeMixin(DataDocumenterMixinBase):
         # An instance variable defined in __init__().
         if self.get_attribute_comment(parent, self.objpath[-1]):  # type: ignore
             return True
+        elif self.is_runtime_instance_attribute_not_commented(parent):
+            return True
         else:
             return False
 
+    def is_runtime_instance_attribute_not_commented(self, parent: Any) -> bool:
+        """Check the subject is an attribute defined in __init__() without comment."""
+        for cls in inspect.getmro(parent):
+            try:
+                module = safe_getattr(cls, '__module__')
+                qualname = safe_getattr(cls, '__qualname__')
+
+                analyzer = ModuleAnalyzer.for_module(module)
+                analyzer.analyze()
+                if qualname and self.objpath:
+                    key = '.'.join([qualname, self.objpath[-1]])
+                    if key in analyzer.tagorder:
+                        return True
+            except (AttributeError, PycodeError):
+                pass
+
+        return None
+
     def import_object(self, raiseerror: bool = False) -> bool:
         """Check the existence of runtime instance attribute when failed to import the
         attribute."""
@@ -2389,6 +2409,13 @@ class RuntimeInstanceAttributeMixin(DataDocumenterMixinBase):
         return (self.object is self.RUNTIME_INSTANCE_ATTRIBUTE or
                 super().should_suppress_value_header())
 
+    def get_doc(self, ignore: int = None) -> Optional[List[List[str]]]:
+        if (self.object is self.RUNTIME_INSTANCE_ATTRIBUTE and
+                self.is_runtime_instance_attribute_not_commented(self.parent)):
+            return None
+        else:
+            return super().get_doc(ignore)  # type: ignore
+
 
 class UninitializedInstanceAttributeMixin(DataDocumenterMixinBase):
     """

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

@@ -8,3 +8,4 @@ class Bar(Foo):
     def __init__(self):
         self.attr2 = None  #: docstring bar
         self.attr3 = None  #: docstring bar
+        self.attr4 = None

tests/test_ext_autodoc_autoattribute.py

@@ -100,6 +100,17 @@ def test_autoattribute_instance_variable_in_alias(app):
     ]
 
 
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_autoattribute_instance_variable_without_comment(app):
+    actual = do_autodoc(app, 'attribute', 'target.instance_variable.Bar.attr4')
+    assert list(actual) == [
+        '',
+        '.. py:attribute:: Bar.attr4',
+        '   :module: target.instance_variable',
+        '',
+    ]
+
+
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_autoattribute_slots_variable_list(app):
     actual = do_autodoc(app, 'attribute', 'target.slots.Foo.attr')