id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37364	Make NullBooleanSelect.format_value() return a list, consistent with ChoiceWidget	Brian Helba	Brian Helba	"`ChoiceWidget.format_value()` is documented (in its docstring) to ""Return selected values as a list"", and every `ChoiceWidget` subclass honors that, except `NullBooleanSelect`, which returns a bare string: `""unknown""`, `""true""`, or `""false""`.

`NullBooleanSelect` does not override `get_context()` or `optgroups()`. It relies on the inherited `ChoiceWidget.optgroups()`, which marks an option as selected with `str(subvalue) in value`. When `value` is a list that is list membership. When `value` is the bare string it becomes a substring test, which only produces correct results because none of `""unknown""`, `""true""`, or `""false""` happens to be a substring of another. The parent's contract is satisfied by accident rather than by design, and it may be confusing for anyone who later customizes the choices or the parent implementation.

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History: #27866 (1.11) changed `ChoiceWidget.format_value()` from returning a set to returning a list but did not touch `NullBooleanSelect`. #17210 (2.2) changed the `NullBooleanSelect` mapping from `1/2/3` to `unknown/true/false` and kept returning a bare string.

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Proposed change: wrap the result in a one-element list, i.e. `[""unknown""]`, `[""true""]`, or `[""false""]`. The rendered HTML should be identical. The only impact would be for third-party code that calls `widget.format_value()` directly and uses the result as a value representation."	Cleanup/optimization	assigned	Forms	dev	Normal			Brian Helba	Unreviewed	1	0	0	0	0	0