[iOS][globalization] Investigate behavioural changes between globalization on iOS and other ICU platforms

[mkhamoyan]

• Go through test cases market as ActiveIssue for PlatformDetection. IsHybridGlobalizationOnApplePlatform in https://github.com/dotnet/runtime/blob/main/src/libraries/Common/tests/Tests/System/StringTests.cs (and others) and investigate if possible to have same behaviour as ICU compare.

• Check Turkish 'I' comparison and check "\u0131" casing.

  • For ICU, we have similar logic implemented at

    runtime/src/native/libs/System.Globalization.Native/pal_casing.c

    Line 135 in 01aa3d9

    dstCodepoint = ((srcCodepoint == (UChar32)0x0069) ? (UChar32)0x0130 : u_toupper(srcCodepoint));

  • and

    runtime/src/native/libs/System.Globalization.Native/pal_casing.c

    Line 91 in 01aa3d9

    dstCodepoint = ((srcCodepoint == (UChar32)0x0131) ? (UChar32)0x0131 : u_toupper(srcCodepoint));

• Check DateTime related behavioural changes.

• Investigate IndexOf behavior differences:

  • The normalization always makes ß == ss, however that shouldn't be the case when IgnoreNonSpace compare options is not used
  • Handling of small latin dz (\U+01F3)

    runtime/src/libraries/System.Runtime/tests/System.Globalization.Tests/CompareInfo/CompareInfoTests.IndexOf.cs

    Line 145 in 54f41ac

    yield return new object[] { s_invariantCompare, "abcdzxyz", "\u01F3", 0, 8, CompareOptions.IgnoreNonSpace, 3, 2 };

  • matchLength returned might be incorrect due to applied normalization [iOS][globalization] Investigate matchLength differences between Apple mobile and other ICU platform returned by (Last)IndexOf, IsSuffix, IsPrefix APIs #112418

In case not possible document behavioural differencies between ICU and Hybrid.

Tests have been marked as ActiveIssue in hybrid mode here #95260

• https://github.com/search?q=repo%3Adotnet%2Fruntime+https%3A%2F%2Fgithub.com%2Fdotnet%2Fruntime%2Fissues%2F95338&type=code

Contributes to #80689

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Issue Details

---

Go through test cases market as ActiveIssue for PlatformDetection.IsNotHybridGlobalizaionOnOSX in https://github.com/dotnet/runtime/blob/main/src/libraries/Common/tests/Tests/System/StringTests.cs and investigate if possible to have same behaviour as ICU compare.
In case not possible document behavioural differencies between ICU and Hybrid.
Tests have been marked as ActiveIssue in hybrid mode here #95260

Contributes to #80689

Author:	mkhamoyan
Assignees:	mkhamoyan
Labels:	area-System.Globalization, os-ios
Milestone:	9.0.0

[matouskozak]

There is ~ 140 cases of test altered or disabled conditioned by HybridGlobalizationOnApplePlatform. We should map all these cases, try implementing the missing functionality and documenting the differences to https://github.com/dotnet/runtime/blob/main/docs/design/features/globalization-hybrid-mode.md. fyi: @vitek-karas