Fix/ambigous charset#30
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Added a mapping of charset aliases to unambiguous ICU names for UConverter.
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@ralflang I am really not sure obout this PR, please conduct a full depth review |
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May 29, 2026
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Silence UConverter “ambiguous encoding” warnings for common charsets
Summary
CharacterSets::toUConverter()to map charset names that ICU treats as ambiguous to stable canonical names before constructingUConverter.toUConverter()for both source and destination encodings inHordeString::_convertCharset()(and the legacyHorde_Stringwrapper).windows-1258and pass-through behavior for unambiguous charsets.Problem
When iconv and mbstring cannot convert a string,
HordeString::_convertCharset()falls back to PHP’s intlUConverter. Several widely used charset labels are ambiguous in ICU: PHP accepts them but emits a warning and picks one canonical mapping, for example:This is commonly triggered by
windows-1258(Vietnamese), which Horde lowercases from MIME labels likeWindows-1258. The warning appears on line 202 ofHordeString.phpand can flood Horde logs during mail/ActiveSync processing even though conversion succeeds.Other affected aliases include
big5-hkscs,shift_jis,tis-620,windows-936, andwindows-950.Solution
CharacterSetswith a small$uconverterMap(afternormalize()) that maps ambiguous aliases to the same ICU canonical names PHP would select anyway (e.g.windows-1258→cp1258, which resolves toibm-5354_P100-1998without a warning).CharacterSets::toUConverter($from)andCharacterSets::toUConverter($to)immediately beforenew UConverter($to, $from).windows-1258.Behavior is unchanged; only log noise is removed.
Files changed
src/CharacterSets.php$uconverterMap,toUConverter()src/HordeString.phptoUConverter()for UConverter fallbacklib/Horde/String.phptest/CharacterSetsTest.phptoUConverter()Test plan
new UConverter('utf-8', 'windows-1258')before/after — confirm noAmbiguous encodingwarning after the patch.HordeString::convertCharset('<html>', 'UTF-8', 'Windows-1258')returns unchanged ASCII (existingtestBug9528).vendor/bin/phpunit test/CharacterSetsTest.phppasses.ibm-5354_P100-1998warnings; confirm logs are clean and message bodies still display correctly for Vietnamese (windows-1258) content.