[LindseyZ1205]

Summary

Adding a dotted key made with key() to an inline table writes invalid TOML:

>>> import tomlkit
>>> doc = tomlkit.parse("a = {b = 1}\n")
>>> doc["a"].add(tomlkit.key(["c", "d"]), 2)
>>> print(tomlkit.dumps(doc))
a = {b = 1,c. =  d = 2}

tomllib rejects it with Invalid initial character for a key part, and tomlkit's own parser with Empty key. append() and item assignment with the key do the same, and so does a new inline table ({c. = d = 2}). On a document or a table, the same key is written as c.d = 2.

The parser leaves the separator empty on every part of a dotted key but the last one, but a key made with key() keeps the default " = " on all of them. InlineTable._render_dotted() writes the separator of those parts after the dot, so it ends up as c. = . This change leaves their separator empty in Container._handle_dotted_key(), so the key has the same shape as a parsed one and is written as c.d = 2.

InlineTable.append() also puts the space before a new entry on the value. For a dotted key the value comes after the prefix, which gave {b = 1,c. d = 2} with only the change above, so the space now goes on the table that the dotted key adds.

test_add_dotted_key_to_inline_table and test_add_dotted_key_to_parsed_inline_table, next to test_add_dotted_key, cover a new and a parsed inline table, including a key under an existing dotted key and a key with three parts. Both fail on master. The full test suite passes with Python 3.14 and 3.12, and so do ruff check and ruff format --check. I found this with a script that makes random edits through the API and reads the output back with tomllib.

Duplicate Check

• I searched the open PRs and found none that already fixes this issue.
• Related open PRs (if any, and why this PR is still needed): Render a dotted key's sub-table inside an inline table as an inline table #616 and Keep an emptied dotted key inside an inline table #664 also fix dotted keys inside inline tables, but for keys that came from the parser: a sub-table added under one (Render a dotted key's sub-table inside an inline table as an inline table #616) and the last key deleted from one (Keep an emptied dotted key inside an inline table #664). With either of them, a key made with key() is still written as c. = d = 2. This PR doesn't touch _render_dotted() and merges cleanly with both.

Agent Drafting Metadata

• Agent: Claude Code
• Model: Claude Opus 5.5
• Notes: