Fix #8602: autodoc: The autodoc-process-docstring event is emitted to the non-datadescriptors unexpectedly

CHANGES

@@ -17,6 +17,8 @@ Bugs fixed
 ----------
 
 * #8164: autodoc: Classes that inherit mocked class are not documented
+* #8602: autodoc: The ``autodoc-process-docstring`` event is emitted to the
+  non-datadescriptors unexpectedly
 
 Testing
 --------

sphinx/ext/autodoc/__init__.py

@@ -2092,18 +2092,36 @@ class NonDataDescriptorMixin(DataDocumenterMixinBase):
               and :value: header will be suppressed unexpectedly.
     """
 
+    def import_object(self, raiseerror: bool = False) -> bool:
+        ret = super().import_object(raiseerror)  # type: ignore
+        if ret and not inspect.isattributedescriptor(self.object):
+            self.non_data_descriptor = True
+        else:
+            self.non_data_descriptor = False
+
+        return ret
+
     def should_suppress_value_header(self) -> bool:
-        return (inspect.isattributedescriptor(self.object) or
+        return (not getattr(self, 'non_data_descriptor', False) or
                 super().should_suppress_directive_header())
 
     def get_doc(self, encoding: str = None, ignore: int = None) -> List[List[str]]:
-        if not inspect.isattributedescriptor(self.object):
+        if getattr(self, 'non_data_descriptor', False):
             # the docstring of non datadescriptor is very probably the wrong thing
             # to display
             return []
         else:
             return super().get_doc(encoding, ignore)  # type: ignore
 
+    def add_content(self, more_content: Optional[StringList], no_docstring: bool = False
+                    ) -> None:
+        if getattr(self, 'non_data_descriptor', False):
+            # the docstring of non datadescriptor is very probably the wrong thing
+            # to display
+            no_docstring = True
+
+        super().add_content(more_content, no_docstring=no_docstring)  # type: ignore
+
 
 class SlotsMixin(DataDocumenterMixinBase):
     """

tests/test_ext_autodoc_events.py

@@ -34,6 +34,23 @@ def on_process_docstring(app, what, name, obj, options, lines):
     ]
 
 
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_process_docstring_for_nondatadescriptor(app):
+    def on_process_docstring(app, what, name, obj, options, lines):
+        raise
+
+    app.connect('autodoc-process-docstring', on_process_docstring)
+
+    actual = do_autodoc(app, 'attribute', 'target.AttCls.a1')
+    assert list(actual) == [
+        '',
+        '.. py:attribute:: AttCls.a1',
+        '   :module: target',
+        '   :value: hello world',
+        '',
+    ]
+
+
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_cut_lines(app):
     app.connect('autodoc-process-docstring',