fix: deleting a key added before a table leaves a blank line behind

tests/test_toml_document.py

@@ -361,6 +361,44 @@ def test_inserting_after_deletion() -> None:
     assert expected == doc.as_string()
 
 
+def test_deleting_key_added_before_a_table_restores_the_document() -> None:
+    content = """[a]
+x = 1
+"""
+
+    doc = parse(content)
+    doc["foo"] = 10
+
+    assert (
+        doc.as_string()
+        == """foo = 10
+
+[a]
+x = 1
+"""
+    )
+
+    del doc["foo"]
+
+    assert doc.as_string() == content
+
+
+def test_adding_keys_before_a_table_separates_them_from_it_once() -> None:
+    doc = parse("[a]\nx = 1\n")
+    doc["foo"] = 10
+    doc["bar"] = 11
+
+    assert (
+        doc.as_string()
+        == """foo = 10
+bar = 11
+
+[a]
+x = 1
+"""
+    )
+
+
 def test_toml_document_with_dotted_keys_inside_table(
     example: Callable[[str], str],
 ) -> None:

tomlkit/container.py

@@ -150,6 +150,16 @@ def _handle_dotted_key(self, key: Key, value: Item) -> None:
         self.append(name, table)
         return
 
+    def _trail_table_separator_on(self, item: Item, before_index: int) -> None:
+        if before_index > 0:
+            previous = self._body[before_index - 1][1]
+            if not isinstance(previous, Whitespace) and previous.trivia.trail.endswith(
+                "\n\n"
+            ):
+                previous.trivia.trail = previous.trivia.trail[:-1]
+
+        item.trivia.trail += "\n"
+
     def _get_last_index_before_table(self) -> int:
         last_index = -1
         for i, (k, v) in enumerate(self._body):
@@ -388,7 +398,13 @@ def append(
 
             if last_index < len(self._body):
                 after_item = self._body[last_index][1]
-                if not (
+                if (
+                    not is_table
+                    and isinstance(after_item, Table)
+                    and "\n" not in after_item.trivia.indent
+                ):
+                    self._trail_table_separator_on(item, before_index=last_index)
+                elif not (
                     isinstance(after_item, Whitespace)
                     or "\n" in after_item.trivia.indent
                 ):