Fix #6436: napoleon: "Unknown target name" error

CHANGES

@@ -20,6 +20,8 @@ Bugs fixed
   immediately preceding section title by pagebreak
 * #6448: autodoc: crashed when autodocumenting classes with ``__slots__ = None``
 * #6452: autosummary: crashed when generating document of properties
+* #6436: napoleon: "Unknown target name" error if variable name ends with
+  underscore
 
 Testing
 --------

sphinx/ext/napoleon/docstring.py

@@ -328,6 +328,9 @@ class GoogleDocstring:
 
     def _escape_args_and_kwargs(self, name):
         # type: (str) -> str
+        if name.endswith('_'):
+            name = name[:-1] + r'\_'
+
         if name[:2] == '**':
             return r'\*\*' + name[2:]
         elif name[:1] == '*':

tests/test_ext_napoleon_docstring.py

@@ -1351,8 +1351,8 @@ arg_ : type
 """
 
         expected = """
-:ivar arg_: some description
-:vartype arg_: type
+:ivar arg\\_: some description
+:vartype arg\\_: type
 """
 
         config = Config(napoleon_use_ivar=True)