add option for autodoc to hide undocumented parameters but show undocumented return types

CHANGES

@@ -61,6 +61,8 @@ Features added
 * #8417: autodoc: ``:inherited-members:`` option now takes multiple classes.  It
   allows to suppress inherited members of several classes on the module at once
   by specifying the option to :rst:dir:`automodule` directive
+* #9792: autodoc: Add new option for ``autodoc_typehints_description_target`` to
+  include undocumented return values but not undocumented parameters.
 * #10028: Removed internal usages of JavaScript frameworks (jQuery and
   underscore.js) and modernised ``doctools.js`` and ``searchtools.js`` to
   EMCAScript 2018.

doc/usage/extensions/autodoc.rst

@@ -634,8 +634,16 @@ There are also config values that you can set:
    When set to ``"documented"``, types will only be documented for a parameter
    or a return value that is already documented by the docstring.
 
+   With ``"documented_params"``, parameter types will only be annotated if the
+   parameter is documented in the docstring. The return type is always
+   annotated (except if it is ``None``).
+
    .. versionadded:: 4.0
 
+   .. versionadded:: 5.0
+
+      New option ``'documented_params'`` is added.
+
 .. confval:: autodoc_type_aliases
 
    A dictionary for users defined `type aliases`__ that maps a type name to the

sphinx/ext/autodoc/__init__.py

@@ -2886,7 +2886,7 @@ def setup(app: Sphinx) -> Dict[str, Any]:
     app.add_config_value('autodoc_typehints', "signature", True,
                          ENUM("signature", "description", "none", "both"))
     app.add_config_value('autodoc_typehints_description_target', 'all', True,
-                         ENUM('all', 'documented'))
+                         ENUM('all', 'documented', 'documented_params'))
     app.add_config_value('autodoc_type_aliases', {}, True)
     app.add_config_value('autodoc_typehints_format', "short", 'env',
                          ENUM("fully-qualified", "short"))

sphinx/ext/autodoc/typehints.py

@@ -60,8 +60,14 @@ def merge_typehints(app: Sphinx, domain: str, objtype: str, contentnode: Element
         for field_list in field_lists:
             if app.config.autodoc_typehints_description_target == "all":
                 modify_field_list(field_list, annotations[fullname])
+            elif app.config.autodoc_typehints_description_target == "documented_params":
+                augment_descriptions_with_types(
+                    field_list, annotations[fullname], force_rtype=True
+                )
             else:
-                augment_descriptions_with_types(field_list, annotations[fullname])
+                augment_descriptions_with_types(
+                    field_list, annotations[fullname], force_rtype=False
+                )
 
 
 def insert_field_list(node: Element) -> nodes.field_list:
@@ -127,6 +133,7 @@ def modify_field_list(node: nodes.field_list, annotations: Dict[str, str]) -> No
 def augment_descriptions_with_types(
     node: nodes.field_list,
     annotations: Dict[str, str],
+    force_rtype: bool
 ) -> None:
     fields = cast(Iterable[nodes.field], node)
     has_description = set()  # type: Set[str]
@@ -163,10 +170,12 @@ def augment_descriptions_with_types(
 
     # Add 'rtype' if 'return' is present and 'rtype' isn't.
     if 'return' in annotations:
-        if 'return' in has_description and 'return' not in has_type:
+        rtype = annotations['return']
+        if 'return' not in has_type and ('return' in has_description or
+                                         (force_rtype and rtype != "None")):
             field = nodes.field()
             field += nodes.field_name('', 'rtype')
-            field += nodes.field_body('', nodes.paragraph('', annotations['return']))
+            field += nodes.field_body('', nodes.paragraph('', rtype))
             node += field
 
 

tests/test_ext_autodoc_configs.py

@@ -892,6 +892,70 @@ def test_autodoc_typehints_description_no_undoc(app):
             in context)
 
 
+@pytest.mark.sphinx('text', testroot='ext-autodoc',
+                    confoverrides={'autodoc_typehints': "description",
+                                   'autodoc_typehints_description_target': 'documented_params'})
+def test_autodoc_typehints_description_no_undoc_doc_rtype(app):
+    # No :type: will be injected for `incr`, which does not have a description
+    # for its parameters or its return, just :rtype: will be injected due to
+    # autodoc_typehints_description_target. `tuple_args` does describe both, so
+    # :type: and :rtype: will be added. `nothing` has no parameters but a return
+    # type of None, which will be added.
+    (app.srcdir / 'index.rst').write_text(
+        '.. autofunction:: target.typehints.incr\n'
+        '\n'
+        '.. autofunction:: target.typehints.decr\n'
+        '\n'
+        '   :returns: decremented number\n'
+        '\n'
+        '.. autofunction:: target.typehints.tuple_args\n'
+        '\n'
+        '   :param x: arg\n'
+        '   :return: another tuple\n'
+        '\n'
+        '.. autofunction:: target.typehints.Math.nothing\n'
+        '\n'
+        '.. autofunction:: target.typehints.Math.horse\n'
+        '\n'
+        '   :return: nothing\n'
+    )
+    app.build()
+    context = (app.outdir / 'index.txt').read_text()
+    assert ('target.typehints.incr(a, b=1)\n'
+            '\n'
+            '   Return type:\n'
+            '      int\n'
+            '\n'
+            'target.typehints.decr(a, b=1)\n'
+            '\n'
+            '   Returns:\n'
+            '      decremented number\n'
+            '\n'
+            '   Return type:\n'
+            '      int\n'
+            '\n'
+            'target.typehints.tuple_args(x)\n'
+            '\n'
+            '   Parameters:\n'
+            '      **x** (*Tuple**[**int**, **Union**[**int**, **str**]**]*) -- arg\n'
+            '\n'
+            '   Returns:\n'
+            '      another tuple\n'
+            '\n'
+            '   Return type:\n'
+            '      *Tuple*[int, int]\n'
+            '\n'
+            'target.typehints.Math.nothing(self)\n'
+            '\n'
+            'target.typehints.Math.horse(self, a, b)\n'
+            '\n'
+            '   Returns:\n'
+            '      nothing\n'
+            '\n'
+            '   Return type:\n'
+            '      None\n' == context)
+
+
 @pytest.mark.sphinx('text', testroot='ext-autodoc',
                     confoverrides={'autodoc_typehints': "description"})
 def test_autodoc_typehints_description_with_documented_init(app):
@@ -944,6 +1008,31 @@ def test_autodoc_typehints_description_with_documented_init_no_undoc(app):
             '         **x** (*int*) -- Some integer\n' == context)
 
 
+@pytest.mark.sphinx('text', testroot='ext-autodoc',
+                    confoverrides={'autodoc_typehints': "description",
+                                   'autodoc_typehints_description_target': 'documented_params'})
+def test_autodoc_typehints_description_with_documented_init_no_undoc_doc_rtype(app):
+    # see test_autodoc_typehints_description_with_documented_init_no_undoc
+    # returnvalue_and_documented_params should not change class or method
+    # docstring.
+    (app.srcdir / 'index.rst').write_text(
+        '.. autoclass:: target.typehints._ClassWithDocumentedInit\n'
+        '   :special-members: __init__\n'
+    )
+    app.build()
+    context = (app.outdir / 'index.txt').read_text()
+    assert ('class target.typehints._ClassWithDocumentedInit(x)\n'
+            '\n'
+            '   Class docstring.\n'
+            '\n'
+            '   __init__(x)\n'
+            '\n'
+            '      Init docstring.\n'
+            '\n'
+            '      Parameters:\n'
+            '         **x** (*int*) -- Some integer\n' == context)
+
+
 @pytest.mark.sphinx('text', testroot='ext-autodoc',
                     confoverrides={'autodoc_typehints': "description"})
 def test_autodoc_typehints_description_for_invalid_node(app):