fix: Add DottedKey to a super table gives wrong output (#431)

tests/test_toml_document.py

@@ -1293,3 +1293,24 @@ def test_parse_aot_without_ending_newline():
         "foo": {},
         "bar": {},
     }
+
+
+def test_appending_to_super_table():
+    content = """\
+[a.b]
+value = 5
+"""
+
+    doc = parse(content)
+    table_a = doc["a"]
+    table_a.append(tomlkit.key(["c", "d"]), "foo")
+
+    expected = """\
+[a]
+c.d = "foo"
+
+[a.b]
+value = 5
+"""
+
+    assert doc.as_string() == expected

tomlkit/container.py

@@ -521,12 +521,19 @@ def _render_table(self, key: Key, table: Table, prefix: str | None = None) -> st
             if prefix is not None:
                 _key = prefix + "." + _key
 
-        if not table.is_super_table() or (
-            any(
-                not isinstance(v, (Table, AoT, Whitespace, Null))
-                for _, v in table.value.body
+        if (
+            not table.is_super_table()
+            or (
+                any(
+                    not isinstance(v, (Table, AoT, Whitespace, Null))
+                    for _, v in table.value.body
+                )
+                and not key.is_dotted()
+            )
+            or (
+                any(k.is_dotted() for k, v in table.value.body if isinstance(v, Table))
+                and not key.is_dotted()
             )
-            and not key.is_dotted()
         ):
             open_, close = "[", "]"
             if table.is_aot_element():