[wasm][globalization] HybridGlobalization fix bug in change case

docs/design/features/hybrid-globalization.md

@@ -27,6 +27,11 @@ Affected public APIs:
 - TextInfo.ToTitleCase.
 
 Case change with invariant culture uses `toUpperCase` / `toLoweCase` functions that do not guarantee a full match with the original invariant culture.
+Hybrid case change, same as ICU-based, does not support code points expansion e.g. "straße" -> "STRAßE".
+
+- Final sigma behavior correction:
+
+ICU-based case change does not respect final-sigma rule, but hybrid does, so "ΒΌΛΟΣ" -> "βόλος", not "βόλοσ".
 
 **String comparison**
 

src/libraries/System.Globalization/tests/System/Globalization/TextInfoTests.cs

@@ -272,8 +272,17 @@ public static IEnumerable<object[]> ToLower_TestData()
                 // these sorts of expansions, since it would cause string lengths to change when cased,
                 // which is non-intuitive. In addition, there are some context sensitive mappings which
                 // we also don't preform.
-                // Greek Capital Letter Sigma (does not to case to U+03C2 with "final sigma" rule).
+                // Greek Capital Letter Sigma (does not case to U+03C2 with "final sigma" rule).
                 yield return new object[] { cultureName, "\u03A3", "\u03C3" };
+                if (PlatformDetection.IsHybridGlobalizationOnBrowser)
+                {
+                    // JS is using "final sigma" rule correctly - it's costly to unify it with ICU's behavior
+                    yield return new object[] { cultureName, "O\u03A3", "o\u03C2" };
+                }
+                else
+                {
+                    yield return new object[] { cultureName, "O\u03A3", "o\u03C3" };
+                }
             }
 
             foreach (string cultureName in GetTestLocales())
@@ -394,6 +403,8 @@ public static IEnumerable<object[]> ToUpper_TestData()
                 // we also don't preform.
                 // es-zed does not case to SS when uppercased.
                 yield return new object[] { cultureName, "\u00DF", "\u00DF" };
+                yield return new object[] { cultureName, "stra\u00DFe", "STRA\u00DFE" };
+                yield return new object[] { cultureName, "st\uD801\uDC37ra\u00DFe", "ST\uD801\uDC0FRA\u00DFE" };
 
                 // Ligatures do not expand when cased.
                 yield return new object[] { cultureName, "\uFB00", "\uFB00" };

src/mono/wasm/runtime/hybrid-globalization/change-case.ts

@@ -6,18 +6,75 @@ import { monoStringToString, utf16ToStringLoop, stringToUTF16 } from "../strings
 import { MonoObject, MonoObjectRef, MonoString, MonoStringRef } from "../types/internal";
 import { Int32Ptr } from "../types/emscripten";
 import { wrap_error_root, wrap_no_error_root } from "../invoke-js";
+import { localHeapViewU16, setU16_local } from "../memory";
+
+const SURROGATE_HIGHER_START = "\uD800";
+const SURROGATE_HIGHER_END = "\uDBFF";
+const SURROGATE_LOWER_START = "\uDC00";
+const SURROGATE_LOWER_END = "\uDFFF";
 
 export function mono_wasm_change_case_invariant(src: number, srcLength: number, dst: number, dstLength: number, toUpper: number, is_exception: Int32Ptr, ex_address: MonoObjectRef): void {
     const exceptionRoot = mono_wasm_new_external_root<MonoObject>(ex_address);
     try {
         const input = utf16ToStringLoop(src, src + 2 * srcLength);
-        let result = toUpper ? input.toUpperCase() : input.toLowerCase();
+        const result = toUpper ? input.toUpperCase() : input.toLowerCase();
         // Unicode defines some codepoints which expand into multiple codepoints,
         // originally we do not support this expansion
-        if (result.length > dstLength)
-            result = input;
-        stringToUTF16(dst, dst + 2 * dstLength, result);
-        wrap_no_error_root(is_exception, exceptionRoot);
+        if (result.length <= dstLength)
+        {
+            stringToUTF16(dst, dst + 2 * dstLength, result);
+            wrap_no_error_root(is_exception, exceptionRoot);
+            return;
+        }
+
+        // workaround to maintain the ICU-like behavior
+        const heapI16 = localHeapViewU16();
+        let jump = 1;
+        if (toUpper)
+        {
+            for (let i=0; i < input.length; i+=jump)
+            {
+                // surrogate parts have to enter ToUpper/ToLower together to give correct output
+                if (IsSurrogate(input, i))
+                {
+                    jump = 2;
+                    const surrogate = input.substring(i, i+2);
+                    const upperSurrogate = surrogate.toUpperCase();
+                    const appendedSurrogate = upperSurrogate.length > 2 ? surrogate : upperSurrogate;
+                    AppendSurrogateToMemory(heapI16, dst, appendedSurrogate, i);
+
+                }
+                else
+                {
+                    jump = 1;
+                    const upperChar = input[i].toUpperCase();
+                    const appendedChar = upperChar.length > 1 ? input[i] : upperChar;
+                    setU16_local(heapI16, dst + i*2, appendedChar.charCodeAt(0));
+                }
+            }
+        }
+        else
+        {
+            for (let i=0; i < input.length; i+=jump)
+            {
+                if (IsSurrogate(input, i))
+                {
+                    jump = 2;
+                    const surrogate = input.substring(i, i+2);
+                    const upperSurrogate = surrogate.toLowerCase();
+                    const appendedSurrogate = upperSurrogate.length > 2 ? surrogate : upperSurrogate;
+                    AppendSurrogateToMemory(heapI16, dst, appendedSurrogate, i);
+
+                }
+                else
+                {
+                    jump = 1;
+                    const upperChar = input[i].toLowerCase();
+                    const appendedChar = upperChar.length > 1 ? input[i] : upperChar;
+                    setU16_local(heapI16, dst + i*2, appendedChar.charCodeAt(0));
+                }
+            }
+        }
     }
     catch (ex: any) {
         wrap_error_root(is_exception, ex, exceptionRoot);
@@ -35,11 +92,62 @@ export function mono_wasm_change_case(culture: MonoStringRef, src: number, srcLe
         if (!cultureName)
             throw new Error("Cannot change case, the culture name is null.");
         const input = utf16ToStringLoop(src, src + 2 * srcLength);
-        let result = toUpper ? input.toLocaleUpperCase(cultureName) : input.toLocaleLowerCase(cultureName);
-        if (result.length > dstLength)
-            result = input;
+        const result = toUpper ? input.toLocaleUpperCase(cultureName) : input.toLocaleLowerCase(cultureName);
+
+        if (result.length <= input.length)
+        {
+            stringToUTF16(dst, dst + 2 * dstLength, result);
+            wrap_no_error_root(is_exception, exceptionRoot);
+            return;
+        }
+        // workaround to maintain the ICU-like behavior
+        const heapI16 = localHeapViewU16();
+        let jump = 1;
+        if (toUpper)
+        {
+            for (let i=0; i < input.length; i+=jump)
+            {
+                // surrogate parts have to enter ToUpper/ToLower together to give correct output
+                if (IsSurrogate(input, i))
+                {
+                    jump = 2;
+                    const surrogate = input.substring(i, i+2);
+                    const upperSurrogate = surrogate.toLocaleUpperCase(cultureName);
+                    const appendedSurrogate = upperSurrogate.length > 2 ? surrogate : upperSurrogate;
+                    AppendSurrogateToMemory(heapI16, dst, appendedSurrogate, i);
 
-        stringToUTF16(dst, dst + 2 * dstLength, result);
+                }
+                else
+                {
+                    jump = 1;
+                    const upperChar = input[i].toLocaleUpperCase(cultureName);
+                    const appendedChar = upperChar.length > 1 ? input[i] : upperChar;
+                    setU16_local(heapI16, dst + i*2, appendedChar.charCodeAt(0));
+                }
+            }
+        }
+        else
+        {
+            for (let i=0; i < input.length; i+=jump)
+            {
+                // surrogate parts have to enter ToUpper/ToLower together to give correct output
+                if (IsSurrogate(input, i))
+                {
+                    jump = 2;
+                    const surrogate = input.substring(i, i+2);
+                    const upperSurrogate = surrogate.toLocaleLowerCase(cultureName);
+                    const appendedSurrogate = upperSurrogate.length > 2 ? surrogate : upperSurrogate;
+                    AppendSurrogateToMemory(heapI16, dst, appendedSurrogate, i);
+                }
+                else
+                {
+                    jump = 1;
+                    const lowerChar = input[i].toLocaleLowerCase(cultureName);
+                    const appendedChar = lowerChar.length > 1 ? input[i] : lowerChar;
+                    setU16_local(heapI16, dst + i*2, appendedChar.charCodeAt(0));
+                }
+            }
+        }
         wrap_no_error_root(is_exception, exceptionRoot);
     }
     catch (ex: any) {
@@ -49,4 +157,19 @@ export function mono_wasm_change_case(culture: MonoStringRef, src: number, srcLe
         cultureRoot.release();
         exceptionRoot.release();
     }
-}
+}
+
+function IsSurrogate(str: string, startIdx: number) : boolean
+{
+    return SURROGATE_HIGHER_START <= str[startIdx] &&
+        str[startIdx] <= SURROGATE_HIGHER_END &&
+        startIdx+1 < str.length &&
+        SURROGATE_LOWER_START <= str[startIdx+1] &&
+        str[startIdx+1] <= SURROGATE_LOWER_END;
+}
+
+function AppendSurrogateToMemory(heapI16: Uint16Array, dst: number, surrogate: string, idx: number)
+{
+    setU16_local(heapI16, dst + idx*2, surrogate.charCodeAt(0));
+    setU16_local(heapI16, dst + (idx+1)*2, surrogate.charCodeAt(1));
+}