Support ICU v78 changes including IDN and Japanese Meiji era start date

src/libraries/System.Private.CoreLib/src/System/Globalization/JapaneseCalendar.Icu.cs

@@ -58,6 +58,14 @@ public partial class JapaneseCalendar : Calendar
                     return null;
                 }
 
+                if (dt.Year == s_calendarMinValue.Year)
+                {
+                    // adjust the start date to the minimum supported date time
+                    // date 1868/9/8 is actually Meiji 1/1/1 but the actual Gregorian date is 1868/10/23. The 1868/9/8 is used before as a Gregorian era start date
+                    // for JapaneseCalendar but now we are ensuring using the correct 1868/10/23 stored in s_calendarMinValue.
+                    dt = s_calendarMinValue;
+                }
+
                 if (dt < s_calendarMinValue)
                 {
                     // only populate the Eras that are valid JapaneseCalendar date times

src/libraries/System.Private.CoreLib/src/System/Globalization/JapaneseCalendar.cs

@@ -27,12 +27,12 @@ namespace System.Globalization
     /// Calendar support range:
     ///     Calendar    Minimum     Maximum
     ///     ==========  ==========  ==========
-    ///     Gregorian   1868/09/08  9999/12/31
+    ///     Gregorian   1868/10/23  9999/12/31
     ///     Japanese    Meiji 01/01 Reiwa 7981/12/31
     /// </remarks>
     public partial class JapaneseCalendar : Calendar
     {
-        private static readonly DateTime s_calendarMinValue = new DateTime(1868, 9, 8);
+        private static readonly DateTime s_calendarMinValue = new DateTime(1868, 10, 23);
 
         public override DateTime MinSupportedDateTime => s_calendarMinValue;
 

src/libraries/System.Runtime/tests/System.Globalization.Calendars.Tests/JapaneseCalendar/JapaneseCalendarAddMonths.cs

@@ -19,12 +19,12 @@ public static IEnumerable<object[]> AddMonths_TestData()
             yield return new object[] { new DateTime(2007, 1, 1), -1, new DateTime(2006, 12, 1) };
 
             // Boundary values
-            yield return new object[] { new DateTime(1868, 9, 8), 1, new DateTime(1868, 10, 8) };
-            yield return new object[] { new DateTime(1868, 10, 8), -1, new DateTime(1868, 9, 8) };
+            yield return new object[] { new DateTime(1868, 10, 23), 1, new DateTime(1868, 11, 23) };
+            yield return new object[] { new DateTime(1868, 11, 23), -1, new DateTime(1868, 10, 23) };
             yield return new object[] { new DateTime(9999, 11, 30), 1, new DateTime(9999, 12, 30) };
             yield return new object[] { new DateTime(9999, 12, 30), -1, new DateTime(9999, 11, 30) };
             yield return new object[] { DateTime.MaxValue, 0, DateTime.MaxValue };
-            yield return new object[] { new DateTime(1868, 9, 8), 0, new DateTime(1868, 9, 8) };
+            yield return new object[] { new DateTime(1868, 10, 23), 0, new DateTime(1868, 10, 23) };
 
             // Day is not in the month
             yield return new object[] { new DateTime(2006, 10, 31), 1, new DateTime(2006, 11, 30) };

src/libraries/System.Runtime/tests/System.Globalization.Calendars.Tests/System/Globalization/JapaneseCalendarTests.cs

@@ -9,7 +9,7 @@ public class JapaneseCalendarTests : CalendarTestBase
     {
         public override Calendar Calendar => new JapaneseCalendar();
 
-        public override DateTime MinSupportedDateTime => new DateTime(1868, 09, 08);
+        public override DateTime MinSupportedDateTime => new DateTime(1868, 10, 23);
 
         public override bool SkipErasTest => true;
 

src/libraries/System.Runtime/tests/System.Globalization.Extensions.Tests/IdnMapping/Data/Factory.cs

@@ -29,7 +29,9 @@ private static Stream GetIdnaTestTxt()
             // some exception for Windows which released ICU 72.1.0.4 which using Unicode 15.1.
 
             string fileName = null;
-            if (PlatformDetection.ICUVersion >= new Version(76, 0))
+            if (PlatformDetection.ICUVersion >= new Version(78, 0))
+                fileName = "IdnaTest_17.txt";
+            else if (PlatformDetection.ICUVersion >= new Version(76, 0))
                 fileName = "IdnaTest_16.txt";
             else if (PlatformDetection.ICUVersion >= new Version(72, 1, 0, 4))
                 fileName = "IdnaTest_15_1.txt";
@@ -70,7 +72,9 @@ private static IEnumerable<IConformanceIdnaTest> ParseFile(Stream stream, Func<s
 
         private static IConformanceIdnaTest GetConformanceIdnaTest(string line, int lineCount)
         {
-            if (PlatformDetection.ICUVersion >= new Version(76, 0))
+            if (PlatformDetection.ICUVersion >= new Version(78, 0))
+                return new Unicode_17_0_IdnaTest(line, lineCount);
+            else if (PlatformDetection.ICUVersion >= new Version(76, 0))
                 return new Unicode_16_0_IdnaTest(line, lineCount);
             else if (PlatformDetection.ICUVersion >= new Version(72, 1, 0, 4))
                 return new Unicode_15_1_IdnaTest(line, lineCount);

src/libraries/System.Runtime/tests/System.Globalization.Extensions.Tests/IdnMapping/Data/Unicode_17_0/ReadMe.txt

@@ -0,0 +1,14 @@
+# Unicode IDNA Mapping and Test Data
+# Date: 2025-08-15
+# © 2025 Unicode®, Inc.
+# Unicode and the Unicode Logo are registered trademarks of Unicode, Inc. in the U.S. and other countries.
+# For terms of use and license, see https://www.unicode.org/terms_of_use.html
+
+This directory contains final data files for version 17.0.0 of
+UTS #46, Unicode IDNA Compatibility Processing.
+
+It also contains the data file Idna2008.txt listing the 
+IDNA2008_Category Property for the same version.
+The listing matches the "IDNA Derived Property" as defined in RFC 5892.
+
+https://www.unicode.org/reports/tr46/

src/libraries/System.Runtime/tests/System.Globalization.Extensions.Tests/IdnMapping/Data/Unicode_17_0/Unicode_17_0_IdnaTest.cs

@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Text;
+using Xunit;
+
+namespace System.Globalization.Tests
+{
+    /// <summary>
+    /// Class to read data obtained from http://www.unicode.org/Public/idna.  For more information read the information
+    /// contained in Data\Unicode_16_0\IdnaTest_16.txt
+    ///
+    /// The structure of the data set is a semicolon delimited list with the following columns:
+    ///
+    /// Column 1: source -          The source string to be tested
+    /// Column 2: toUnicode -       The result of applying toUnicode to the source,
+    ///                             with Transitional_Processing=false.
+    ///                             A blank value means the same as the source value.
+    /// Column 3: toUnicodeStatus - A set of status codes, each corresponding to a particular test.
+    ///                             A blank value means [] (no errors).
+    /// Column 4: toAsciiN -        The result of applying toASCII to the source,
+    ///                             with Transitional_Processing=false.
+    ///                             A blank value means the same as the toUnicode value.
+    /// Column 5: toAsciiNStatus -  A set of status codes, each corresponding to a particular test.
+    ///                             A blank value means the same as the toUnicodeStatus value.
+    ///                             An explicit [] means no errors.
+    /// Column 6: toAsciiT -        The result of applying toASCII to the source,
+    ///                             with Transitional_Processing=true.
+    ///                             A blank value means the same as the toAsciiN value.
+    /// Column 7: toAsciiTStatus -  A set of status codes, each corresponding to a particular test.
+    ///                             A blank value means the same as the toAsciiNStatus value.
+    ///                             An explicit [] means no errors.
+    ///
+    /// If the value of toUnicode or toAsciiN is the same as source, the column will be blank.
+    /// </summary>
+    public class Unicode_17_0_IdnaTest : Unicode_IdnaTest
+    {
+        public Unicode_17_0_IdnaTest(string line, int lineNumber)
+        {
+            var split = line.Split(';');
+
+            Type = PlatformDetection.IsNlsGlobalization ? IdnType.Transitional : IdnType.Nontransitional;
+
+            Source = EscapedToLiteralString(split[0], lineNumber);
+
+            UnicodeResult = new ConformanceIdnaUnicodeTestResult(EscapedToLiteralString(split[1], lineNumber), Source, EscapedToLiteralString(split[2], lineNumber), string.Empty, Source);
+            ASCIIResult = new ConformanceIdnaTestResult(EscapedToLiteralString(split[3], lineNumber), UnicodeResult.Value, EscapedToLiteralString(split[4], lineNumber), UnicodeResult.StatusValue, Source);
+
+            // NLS uses transitional IDN processing.
+            if (Type == IdnType.Transitional)
+            {
+                ASCIIResult = new ConformanceIdnaTestResult(EscapedToLiteralString(split[5], lineNumber), ASCIIResult.Value, EscapedToLiteralString(split[6], lineNumber), ASCIIResult.StatusValue);
+            }
+
+            LineNumber = lineNumber;
+        }
+    }
+}

src/libraries/System.Runtime/tests/System.Globalization.Extensions.Tests/NlsTests/System.Globalization.Extensions.Nls.Tests.csproj

@@ -23,6 +23,8 @@
              Link="IdnMapping\Data\Unicode_15_1\Unicode_15_1_IdnaTest.cs" />
     <Compile Include="..\IdnMapping\Data\Unicode_16_0\Unicode_16_0_IdnaTest.cs"
              Link="IdnMapping\Data\Unicode_16_0\Unicode_16_0_IdnaTest.cs" />
+    <Compile Include="..\IdnMapping\Data\Unicode_17_0\Unicode_17_0_IdnaTest.cs"
+             Link="IdnMapping\Data\Unicode_17_0\Unicode_17_0_IdnaTest.cs" />
     <Compile Include="..\IdnMapping\IdnMappingIdnaConformanceTests.cs"
              Link="IdnMapping\IdnMappingIdnaConformanceTests.cs" />
     <Compile Include="..\IdnMapping\Data\Factory.cs"
@@ -57,6 +59,7 @@
     <EmbeddedResource Include="..\IdnMapping\Data\Unicode_15_0\IdnaTest_15_0.txt" />
     <EmbeddedResource Include="..\IdnMapping\Data\Unicode_15_1\IdnaTest_15_1.txt" />
     <EmbeddedResource Include="..\IdnMapping\Data\Unicode_16_0\IdnaTest_16.txt" />
+    <EmbeddedResource Include="..\IdnMapping\Data\Unicode_17_0\IdnaTest_17.txt" />
     <EmbeddedResource Include="..\Normalization\Data\win8.txt">
       <LogicalName>NormalizationDataWin8</LogicalName>
     </EmbeddedResource>

src/libraries/System.Runtime/tests/System.Globalization.Extensions.Tests/System.Globalization.Extensions.Tests.csproj

@@ -13,6 +13,7 @@
     <Compile Include="IdnMapping\Data\Unicode_15_0\Unicode_15_0_IdnaTest.cs" />
     <Compile Include="IdnMapping\Data\Unicode_15_1\Unicode_15_1_IdnaTest.cs" />
     <Compile Include="IdnMapping\Data\Unicode_16_0\Unicode_16_0_IdnaTest.cs" />
+    <Compile Include="IdnMapping\Data\Unicode_17_0\Unicode_17_0_IdnaTest.cs" />
     <Compile Include="IdnMapping\IdnMappingIdnaConformanceTests.cs" />
     <Compile Include="IdnMapping\Data\Factory.cs" />
     <Compile Include="IdnMapping\Data\ConformanceIdnaTestResult.cs" />
@@ -34,6 +35,7 @@
     <EmbeddedResource Include="IdnMapping\Data\Unicode_15_0\IdnaTest_15_0.txt" />
     <EmbeddedResource Include="IdnMapping\Data\Unicode_15_1\IdnaTest_15_1.txt" />
     <EmbeddedResource Include="IdnMapping\Data\Unicode_16_0\IdnaTest_16.txt" />
+    <EmbeddedResource Include="IdnMapping\Data\Unicode_17_0\IdnaTest_17.txt" />
     <EmbeddedResource Include="Normalization\Data\win8.txt">
       <LogicalName>NormalizationDataWin8</LogicalName>
     </EmbeddedResource>