Fix #7461: py domain: fails with IndexError for empty tuple in type annotation

3 files changed, 19 insertions, 5 deletions

diff --git a/CHANGES b/CHANGES
index 84d3c2669..31bc95082 100644
--- a/CHANGES
+++ b/CHANGES
@@ -16,6 +16,8 @@ Features added
 Bugs fixed
 ----------
 
+* #7461: py domain: fails with IndexError for empty tuple in type annotation
+
 Testing
 --------
 
diff --git a/sphinx/domains/python.py b/sphinx/domains/python.py
index 07a66fe22..19da49ac6 100644
--- a/sphinx/domains/python.py
+++ b/sphinx/domains/python.py
@@ -105,11 +105,16 @@ def _parse_annotation(annotation: str) -> List[Node]:
             result.append(addnodes.desc_sig_punctuation('', ']'))
             return result
         elif isinstance(node, ast.Tuple):
-            result = []
-            for elem in node.elts:
-                result.extend(unparse(elem))
-                result.append(addnodes.desc_sig_punctuation('', ', '))
-            result.pop()
+            if node.elts:
+                result = []
+                for elem in node.elts:
+                    result.extend(unparse(elem))
+                    result.append(addnodes.desc_sig_punctuation('', ', '))
+                result.pop()
+            else:
+                result = [addnodes.desc_sig_punctuation('', '('),
+                          addnodes.desc_sig_punctuation('', ')')]
+
             return result
         else:
             raise SyntaxError  # unsupported syntax
diff --git a/tests/test_domain_py.py b/tests/test_domain_py.py
index cc3d3cf53..e330ba634 100644
--- a/tests/test_domain_py.py
+++ b/tests/test_domain_py.py
@@ -255,6 +255,13 @@ def test_parse_annotation():
                           [pending_xref, "int"],
                           [desc_sig_punctuation, "]"]))
 
+    doctree = _parse_annotation("Tuple[()]")
+    assert_node(doctree, ([pending_xref, "Tuple"],
+                          [desc_sig_punctuation, "["],
+                          [desc_sig_punctuation, "("],
+                          [desc_sig_punctuation, ")"],
+                          [desc_sig_punctuation, "]"]))
+
     doctree = _parse_annotation("Callable[[int, int], int]")
     assert_node(doctree, ([pending_xref, "Callable"],
                           [desc_sig_punctuation, "["],