From fe46347f8960c65825ed47ec70ddc6ce19331d2f Mon Sep 17 00:00:00 2001
From: Vincent Gao <gaobing1230@gmail.com>
Date: Thu, 18 Jun 2026 23:19:30 +0200
Subject: [PATCH] Fix stale dotted-key prefix when replacing a table value with
 a plain dict
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After parsing 'fruit.apple = true', the key 'fruit' in the document
body retained _dotted=True from _handle_dotted_key.  When the entire
table was then replaced via doc['fruit'] = {'a': 1}, _replace_at
reused the old key object (same name + same kind), keeping the stale
_dotted flag.  This caused rendering to both emit a [fruit] header
(because the new table is not a super-table) and prefix every child
with 'fruit.' (because key.is_dotted() was true), producing the
invalid output '[fruit]\nfruit.a = 1' instead of 'a = 1'.

Fix: clear _dotted on the reused key in _replace_at.  The dotted
heritage belongs to the original parse — a full table replacement
gets fresh rendering behaviour.  Incremental modifications (like
doc['fruit']['banana'] = 2) are unaffected because they don't
reach the document-level _replace_at path.
---
 CHANGELOG.md         |  1 +
 tests/test_items.py  | 12 ++++++++++++
 tomlkit/container.py |  1 +
 3 files changed, 14 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 26584a1c..e8552dc6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,7 @@
 - Fix `comment()` producing invalid TOML for a multiline string by prefixing every line with `#`, not just the first. ([#449](https://github.com/python-poetry/tomlkit/issues/449))
 - Fix the separator comma being swallowed by a trailing comment when appending a key to a multiline inline table, leaving the new key without a separator so the result no longer round-trips. ([#512](https://github.com/python-poetry/tomlkit/issues/512))
 - Fix a `KeyAlreadyPresent` error when parsing or accessing an out-of-order table whose array-of-tables elements are split across the table's parts. ([#505](https://github.com/python-poetry/tomlkit/issues/505))
+- Fix a stale dotted-key prefix when replacing a dotted-key table value with a plain dict, where ``fruit.apple = true`` followed by ``doc['fruit'] = {'a': 1}`` would render a ``[fruit]`` header followed by the wrongly dotted ``fruit.a = 1`` instead of ``a = 1``. ([#524](https://github.com/python-poetry/tomlkit/issues/524))
 
 ## [0.15.0] - 2026-05-10
 
diff --git a/tests/test_items.py b/tests/test_items.py
index b4653e72..65304017 100644
--- a/tests/test_items.py
+++ b/tests/test_items.py
@@ -1236,6 +1236,18 @@ def test_serialize_table_with_dotted_key() -> None:
     assert parent.as_string() == "[a]\nb.c = 1\n"
 
 
+def test_replacing_dotted_key_table_clears_prefix() -> None:
+    """Replacing a dotted-key table with a plain dict should not carry
+    over the dotted prefix to the new children (#524)."""
+    doc = parse("fruit.apple = true\n")
+    doc["fruit"] = {"a": 1}
+    rendered = doc.as_string()
+    assert rendered == "[fruit]\na = 1\n"
+    # Round-trip
+    doc2 = parse(rendered)
+    assert doc2["fruit"]["a"] == 1
+
+
 def test_not_showing_parent_header_for_super_table() -> None:
     doc = api.document()
 
diff --git a/tomlkit/container.py b/tomlkit/container.py
index 75e09018..314100db 100644
--- a/tomlkit/container.py
+++ b/tomlkit/container.py
@@ -829,6 +829,7 @@ def _replace_at(
                 new_key = SingleKey(new_key)
             else:  # Inherit the sep of the old key
                 new_key = k
+                new_key._dotted = False  # Reset dotted heritage on full replacement
 
         del self._map[k]
         self._map[new_key] = idx