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Wkhanex
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Oct 14, 2026
Wkhanex
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Single-quoted replacement works at root, table, inline-table and out-of-order dotted-key locations. Representable replacements keep their literal quotes; values containing an apostrophe or newline fall back to valid output, and backslashes/double quotes roundtrip correctly.
Checked 87ced370034c with standalone Python 3.12.14 checks (52 passing assertions). I haven't run the full upstream suite.
frostming
reviewed
Oct 16, 2026
| def __setitem__(self, key: Key | str, value: Any) -> None: | ||
| if key in self: | ||
| old_key = next(filter(lambda k: k == key, self._map)) | ||
| if isinstance(value, str) and not isinstance(value, String): |
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This is run twice, please reduce one.
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Summary
Related to #325.
When editing a parsed TOML table, assigning a plain Python string currently replaces single quotes with double quotes:
bar = 'baz'becomesbar = "quux"after assigning"quux". This adds formatting changes to an otherwise simple configuration edit.Preserve single-line literal quoting for replacements that can be represented that way. Values containing an apostrophe, newline, or forbidden control character still use basic strings, which provide the necessary escaping. Explicit
tomlkit.string(...)values keep the caller's quote choice. New fields, multiline strings, and array element assignments keep their existing behavior.The conversion is shared by document, table, and inline-table assignment. This is needed because tables convert Python strings to TOML items before passing them to the underlying container; checking only the final replacement method would miss the original issue's table example.
Regression tests check root, ordinary, inline, and out-of-order tables, preserving comments, spacing, key order and line endings. They also check the actual values after serialization and reparsing, explicit quote choices, and values requiring escaping. These are additional checks for this change, alongside the project's existing suite.
On Windows with Python 3.12.2, all 1,088 tests pass, including 20 new regression cases (10 fail on the baseline). All six pre-commit hooks pass. Mypy reports the same 29 errors on the baseline and the fix. Alternating local measurements found about 0.98–2.50 microseconds of extra cost per string assignment (6.0–15.8%); parsing 30 fields differed by 0.25%.
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