From 785f4d695cfca0eeb537c92166808bc9f187d8c0 Mon Sep 17 00:00:00 2001
From: Takeshi KOMIYA <i.tkomiya@gmail.com>
Date: Sat, 3 Oct 2020 12:00:33 +0900
Subject: [PATCH] Fix #7964: autodoc: Tuple in default value is wrongly
 rendered

This implements tuple literal support to sphinx.pycode.ast.unparse().
---
 CHANGES                  |  1 +
 sphinx/pycode/ast.py     | 18 ++++++++++++++++--
 tests/test_pycode_ast.py |  2 +-
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/CHANGES b/CHANGES
index 22876d43b1c..bfe8910d16b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -34,6 +34,7 @@ Bugs fixed
   by string not ending with blank lines
 * #8142: autodoc: Wrong constructor signature for the class derived from
   typing.Generic
+* #7964: autodoc: Tuple in default value is wrongly rendered
 * #8192: napoleon: description is disappeared when it contains inline literals
 * #8142: napoleon: Potential of regex denial of service in google style docs
 * #8169: LaTeX: pxjahyper loaded even when latex_engine is not platex
diff --git a/sphinx/pycode/ast.py b/sphinx/pycode/ast.py
index 9bafff11c1a..2583448d5d7 100644
--- a/sphinx/pycode/ast.py
+++ b/sphinx/pycode/ast.py
@@ -166,14 +166,28 @@ def visit_Set(self, node: ast.Set) -> str:
         return "{" + ", ".join(self.visit(e) for e in node.elts) + "}"
 
     def visit_Subscript(self, node: ast.Subscript) -> str:
-        return "%s[%s]" % (self.visit(node.value), self.visit(node.slice))
+        def is_simple_tuple(value: ast.AST) -> bool:
+            return (
+                isinstance(value, ast.Tuple) and
+                bool(value.elts) and
+                not any(isinstance(elt, ast.Starred) for elt in value.elts)
+            )
+
+        if is_simple_tuple(node.slice):
+            elts = ", ".join(self.visit(e) for e in node.slice.elts)  # type: ignore
+            return "%s[%s]" % (self.visit(node.value), elts)
+        elif isinstance(node.slice, ast.Index) and is_simple_tuple(node.slice.value):
+            elts = ", ".join(self.visit(e) for e in node.slice.value.elts)  # type: ignore
+            return "%s[%s]" % (self.visit(node.value), elts)
+        else:
+            return "%s[%s]" % (self.visit(node.value), self.visit(node.slice))
 
     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)
+            return "(" + ", ".join(self.visit(e) for e in node.elts) + ")"
         else:
             return "()"
 
diff --git a/tests/test_pycode_ast.py b/tests/test_pycode_ast.py
index 9b12d24d5f6..32a784b7419 100644
--- a/tests/test_pycode_ast.py
+++ b/tests/test_pycode_ast.py
@@ -53,7 +53,7 @@
     ("+ 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)
 ])
 def test_unparse(source, expected):