Render emptied dotted tables inside inline tables as empty tables

tests/test_items.py

@@ -1258,6 +1258,46 @@ def test_adding_to_nested_dotted_key_inside_inline_table() -> None:
     assert parse(rendered).as_string() == rendered
 
 
+def test_deleting_last_key_under_dotted_key_in_inline_table() -> None:
+    # The emptied dotted table still exists, so it must render as an empty
+    # inline table; emitting nothing leaves a dangling separator and produces
+    # invalid TOML like ``{a = 1, , d = 1}``.
+    doc = parse("t = {a = 1, b.c = 2, d = 3}\n")
+    del doc["t"]["b"]["c"]
+    rendered = doc.as_string()
+    assert rendered == "t = {a = 1, b = {}, d = 3}\n"
+    assert parse(rendered) == {"t": {"a": 1, "b": {}, "d": 3}}
+    assert parse(rendered).as_string() == rendered
+
+    doc = parse("t = {b.c = 2, a = 1}\n")
+    del doc["t"]["b"]["c"]
+    rendered = doc.as_string()
+    assert rendered == "t = {b = {}, a = 1}\n"
+    assert parse(rendered) == {"t": {"b": {}, "a": 1}}
+
+    doc = parse("t = {a = 1, b.c = 2}\n")
+    del doc["t"]["b"]["c"]
+    rendered = doc.as_string()
+    assert rendered == "t = {a = 1, b = {}}\n"
+    assert parse(rendered) == {"t": {"a": 1, "b": {}}}
+
+    doc = parse("t = {b.c = 2}\n")
+    del doc["t"]["b"]["c"]
+    rendered = doc.as_string()
+    assert rendered == "t = {b = {}}\n"
+    assert parse(rendered) == {"t": {"b": {}}}
+
+
+def test_deleting_nested_key_under_dotted_key_in_inline_table() -> None:
+    doc = parse("t = {x = 1, a.b.c = 2, y = 3}\n")
+    del doc["t"]["a"]["b"]["c"]
+
+    rendered = doc.as_string()
+    assert rendered == "t = {x = 1, a.b = {}, y = 3}\n"
+    assert parse(rendered) == {"t": {"x": 1, "a": {"b": {}}, "y": 3}}
+    assert parse(rendered).as_string() == rendered
+
+
 def test_appending_to_comma_first_array_does_not_double_separator() -> None:
     doc = parse(
         """\

tomlkit/items.py

@@ -2181,8 +2181,11 @@ def as_string(self) -> str:
             if k.is_dotted() and isinstance(v, Table):
                 # A table materialized from a dotted key renders one
                 # `prefix.child = value` pair per child, so that keys added
-                # after parsing stay attached to the dotted prefix.
-                rendered = ", ".join(self._render_dotted(k, v))
+                # after parsing stay attached to the dotted prefix. When all
+                # children were removed the table itself still exists, so it
+                # must render as an empty inline table to stay valid TOML.
+                dotted = self._render_dotted(k, v)
+                rendered = ", ".join(dotted) if dotted else f"{k.as_string()} = {{}}"
             else:
                 rendered = (
                     f"{k.as_string() + ('.' if k.is_dotted() else '')}"
@@ -2220,7 +2223,13 @@ def _render_dotted(self, key: Key, table: Table) -> list[str]:
             if k is None:
                 continue
             if isinstance(v, Table):
-                parts.extend(f"{prefix}{sub}" for sub in self._render_dotted(k, v))
+                sub = self._render_dotted(k, v)
+                if sub:
+                    parts.extend(f"{prefix}{s}" for s in sub)
+                else:
+                    # The nested table exists but renders nothing after its
+                    # last child was removed; emit it as an empty inline table.
+                    parts.append(f"{prefix}{k.as_string()} = {{}}")
             else:
                 trail = v.trivia.trail.replace("\n", "")
                 parts.append(