Fix sphinx-doc#9648: autodoc: *args and **kwargs entries are duplicated

In basic usage of autodoc (docstring), `args` and `kwargs` arguments
are marked up without stars.  But numpydoc style recommends to mark
them up with stars.

This adds support for starred arguments in docstrings to
`autodoc_typehints` feature.

CHANGES

@@ -16,6 +16,9 @@ Features added
 Bugs fixed
 ----------
 
+* #9648: autodoc: ``*args`` and ``**kwargs`` entries are duplicated when
+  ``autodoc_typehints="description"``
+
 Testing
 --------
 

sphinx/ext/autodoc/typehints.py

@@ -111,7 +111,15 @@ def modify_field_list(node: nodes.field_list, annotations: Dict[str, str]) -> No
         if name == 'return':
             continue
 
-        arg = arguments.get(name, {})
+        if '*' + name in arguments:
+            name = '*' + name
+            arguments.get(name)
+        elif '**' + name in arguments:
+            name = '**' + name
+            arguments.get(name)
+        else:
+            arg = arguments.get(name, {})
+
         if not arg.get('type'):
             field = nodes.field()
             field += nodes.field_name('', 'type ' + name)
@@ -159,13 +167,19 @@ def augment_descriptions_with_types(
             has_type.add('return')
 
     # Add 'type' for parameters with a description but no declared type.
-    for name in annotations:
+    for name, annotation in annotations.items():
         if name in ('return', 'returns'):
             continue
+
+        if '*' + name in has_description:
+            name = '*' + name
+        elif '**' + name in has_description:
+            name = '**' + name
+
         if name in has_description and name not in has_type:
             field = nodes.field()
             field += nodes.field_name('', 'type ' + name)
-            field += nodes.field_body('', nodes.paragraph('', annotations[name]))
+            field += nodes.field_body('', nodes.paragraph('', annotation))
             node += field
 
     # Add 'rtype' if 'return' is present and 'rtype' isn't.

tests/roots/test-ext-napoleon/conf.py

@@ -0,0 +1,5 @@
+import os
+import sys
+
+sys.path.insert(0, os.path.abspath('.'))
+extensions = ['sphinx.ext.napoleon']

tests/roots/test-ext-napoleon/index.rst

@@ -0,0 +1,6 @@
+test-ext-napoleon
+=================
+
+.. toctree::
+
+   typehints

tests/roots/test-ext-napoleon/target/typehints.py

@@ -0,0 +1,11 @@
+def hello(x: int, *args: int, **kwargs: int) -> None:
+    """
+    Parameters
+    ----------
+    x
+        X
+    *args
+        Additional arguments.
+    **kwargs
+        Extra arguments.
+    """

tests/roots/test-ext-napoleon/typehints.rst

@@ -0,0 +1,5 @@
+typehints
+=========
+
+.. automodule:: target.typehints
+   :members:

tests/test_ext_napoleon_docstring.py

@@ -2593,3 +2593,48 @@ def test_pep526_annotations(self):
 """
         print(actual)
         assert expected == actual
+
+
+@pytest.mark.sphinx('text', testroot='ext-napoleon',
+                    confoverrides={'autodoc_typehints': 'description',
+                                   'autodoc_typehints_description_target': 'all'})
+def test_napoleon_and_autodoc_typehints_description_all(app, status, warning):
+    app.build()
+    content = (app.outdir / 'typehints.txt').read_text(encoding='utf-8')
+    assert content == (
+        'typehints\n'
+        '*********\n'
+        '\n'
+        'target.typehints.hello(x, *args, **kwargs)\n'
+        '\n'
+        '   Parameters:\n'
+        '      * **x** (*int*) -- X\n'
+        '\n'
+        '      * ***args** (*int*) -- Additional arguments.\n'
+        '\n'
+        '      * ****kwargs** (*int*) -- Extra arguments.\n'
+        '\n'
+        '   Return type:\n'
+        '      None\n'
+    )
+
+
+@pytest.mark.sphinx('text', testroot='ext-napoleon',
+                    confoverrides={'autodoc_typehints': 'description',
+                                   'autodoc_typehints_description_target': 'documented_params'})
+def test_napoleon_and_autodoc_typehints_description_documented_params(app, status, warning):
+    app.build()
+    content = (app.outdir / 'typehints.txt').read_text(encoding='utf-8')
+    assert content == (
+        'typehints\n'
+        '*********\n'
+        '\n'
+        'target.typehints.hello(x, *args, **kwargs)\n'
+        '\n'
+        '   Parameters:\n'
+        '      * **x** (*int*) -- X\n'
+        '\n'
+        '      * ***args** (*int*) -- Additional arguments.\n'
+        '\n'
+        '      * ****kwargs** (*int*) -- Extra arguments.\n'
+    )