Fix culture creation with undetermined lang tag #115166
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Pull Request Overview
This PR fixes the behavior of creating CultureInfo objects from undetermined language tags like "und-US" by restoring the removed "und" subtag.
- Added new tests in CultureInfoCtor.cs to validate the undetermined language tag behavior.
- Updated CultureData.Icu.cs to include the original input name in NormalizeCultureName and to restore "und" as necessary.
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
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| src/libraries/System.Runtime/tests/System.Globalization.Tests/CultureInfo/CultureInfoCtor.cs | Added tests for verifying normalization of undetermined language tags. |
| src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.Icu.cs | Modified NormalizeCultureName to accept the original name and restore the "und" prefix when needed. |
Comments suppressed due to low confidence (1)
src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.Icu.cs:50
- Ensure that the variable 'changed' is properly declared and in scope. If it is not declared in this method or a broader scope, this line will cause a compilation error.
changed = true;
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Tagging subscribers to this area: @dotnet/area-system-globalization |
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@mcdurdin would you be interested to test the fix when we merge it? |
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CC @xadxura |
Yes, sure, that would be great thanks. |
| [InlineData("und-us", "und-US", "und-US")] | ||
| [InlineData("und-us_tradnl", "und-US", "und-US_tradnl")] | ||
| [InlineData("und-es-u-co-phoneb", "und-ES", "und-ES_phoneb")] | ||
| [InlineData("und-es-t-something", "und-ES", "und-ES")] |
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Is it possible to add a test for und-fonipa? That's a common tag for IPA, referenced on Wikipedia for example: https://en.wikipedia.org/wiki/International_Phonetic_Alphabet#IETF_language_tags
Fixes #98543
This change enables support for creating
CultureInfoobjects using an undetermined language tag likeund-US.The root issue is that ICU's
uloc_getNamereturns malformed names such as_USwhen givenund-US. This fix ensures the removed language subtagundis preserved and restored in the result.A more comprehensive alternative—switching to
uloc_toLanguageTag—was considered, but it may introduce compatibility and performance concerns. It would also require a broader audit of how we normalize culture names around ICU usage. We can revisit that approach if more issues like this one are discovered.