Fix #9364: autodoc: 1-element tuple on the defarg is wrongly rendered

CHANGES

@@ -65,6 +65,8 @@ Bugs fixed
 * #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
+* #9364: autodoc: single element tuple on the default argument value is wrongly
+  rendered
 * #9317: html: Pushing left key causes visiting the next page at the first page
 * #9270: html theme : pyramid theme generates incorrect logo links
 * #9217: manpage: The name of manpage directory that is generated by

sphinx/pycode/ast.py

@@ -213,10 +213,12 @@ def visit_UnaryOp(self, node: ast.UnaryOp) -> str:
         return "%s %s" % (self.visit(node.op), self.visit(node.operand))
 
     def visit_Tuple(self, node: ast.Tuple) -> str:
-        if node.elts:
-            return "(" + ", ".join(self.visit(e) for e in node.elts) + ")"
-        else:
+        if len(node.elts) == 0:
             return "()"
+        elif len(node.elts) == 1:
+            return "(%s,)" % self.visit(node.elts[0])
+        else:
+            return "(" + ", ".join(self.visit(e) for e in node.elts) + ")"
 
     if sys.version_info < (3, 8):
         # these ast nodes were deprecated in python 3.8

tests/test_pycode_ast.py

@@ -53,8 +53,9 @@
     ("+ a", "+ a"),                             # UAdd
     ("- 1", "- 1"),                             # UnaryOp
     ("- a", "- a"),                             # USub
-    ("(1, 2, 3)", "(1, 2, 3)"),                   # Tuple
+    ("(1, 2, 3)", "(1, 2, 3)"),                 # Tuple
     ("()", "()"),                               # Tuple (empty)
+    ("(1,)", "(1,)"),                           # Tuple (single item)
 ])
 def test_unparse(source, expected):
     module = ast.parse(source)