Avoid loading ICU data early during mono startup

eng/testing/linker/trimmingTests.targets

@@ -156,7 +156,7 @@
       <Output TaskParameter="ExitCode" PropertyName="ExecutionExitCode" />
     </Exec>
 
-    <Error Condition="'$(ExecutionExitCode)' != '100'" Text="Error: [Failed Test]: %(TestConsoleApps.ProjectCompileItems). The Command %(TestConsoleApps.TestCommand) return a non-success exit code." ContinueOnError="ErrorAndContinue" />
+    <Error Condition="'$(ExecutionExitCode)' != '100'" Text="Error: [Failed Test]: %(TestConsoleApps.ProjectCompileItems). The Command %(TestConsoleApps.TestCommand) return a non-success exit code $(ExecutionExitCode)." ContinueOnError="ErrorAndContinue" />
   </Target>
 
   <Target Name="Build" DependsOnTargets="ExecuteApplications" />

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

@@ -630,7 +630,11 @@ private static CultureData CreateCultureWithInvariantData()
             // all available calendar type(s).  The first one is the default calendar
             invariant._waCalendars = new CalendarId[] { CalendarId.GREGORIAN };
 
+#if TARGET_BROWSER
+            if (!GlobalizationMode.InvariantFast)
+#else
             if (!GlobalizationMode.Invariant)
+#endif
             {
                 // Store for specific data about each calendar
                 invariant._calendars = new CalendarData[CalendarData.MAX_CALENDARS];
@@ -648,7 +652,11 @@ private static CultureData CreateCultureWithInvariantData()
             invariant._iDefaultMacCodePage = 10000;         // default macintosh code page
             invariant._iDefaultEbcdicCodePage = 037;        // default EBCDIC code page
 
+#if TARGET_BROWSER
+            if (GlobalizationMode.InvariantFast)
+#else
             if (GlobalizationMode.Invariant)
+#endif
             {
                 invariant._sLocalizedCountry = invariant._sNativeCountry;
             }

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

@@ -25,6 +25,12 @@ private static partial class Settings
         // This allows for the whole Settings nested class to be trimmed when Invariant=true, and allows for the Settings
         // static cctor (on Unix) to be preserved when Invariant=false.
         internal static bool Invariant => Settings.Invariant;
+
+#if TARGET_BROWSER
+        // same as GlobalizationMode.Invariant but doesn't trigger ICU load in GlobalizationMode.Settings.cctor during runtime startup
+        internal static bool InvariantFast { get; } = AppContextConfigHelper.GetBooleanConfig("System.Globalization.Invariant", "DOTNET_SYSTEM_GLOBALIZATION_INVARIANT");
+#endif
+
 #if TARGET_MACCATALYST || TARGET_IOS || TARGET_TVOS || TARGET_BROWSER
         internal static bool Hybrid => Settings.Hybrid;
 #endif

src/libraries/System.Runtime/tests/System.Runtime.Tests/TrimmingTests/InvariantGlobalizationTrue.cs

@@ -27,12 +27,13 @@ static int Main(string[] args)
         {
             return -3;
         }
-        
+
         // Ensure the internal GlobalizationMode class is trimmed correctly.
         Type globalizationMode = GetCoreLibType("System.Globalization.GlobalizationMode");
 
-        if (OperatingSystem.IsWindows())
+        if (OperatingSystem.IsWindows() || OperatingSystem.IsBrowser())
         {
+            string allowedMember = OperatingSystem.IsWindows() ? "UseNls" : "InvariantFast";
             foreach (MemberInfo member in globalizationMode.GetMembers(allStatics))
             {
                 // properties and their backing getter methods are OK
@@ -41,8 +42,8 @@ static int Main(string[] args)
                     continue;
                 }
 
-                // Windows still contains a static cctor and a backing field for UseNls.
-                if (member is ConstructorInfo || (member is FieldInfo field && field.Name.Contains("UseNls")))
+                // Windows still contains a static cctor and a backing field for UseNls or InvariantFast.
+                if (member is ConstructorInfo || (member is FieldInfo field && field.Name.Contains(allowedMember)))
                 {
                     continue;
                 }
@@ -52,10 +53,10 @@ static int Main(string[] args)
                 return -4;
             }
         }
-        // On non Windows platforms, the full type is trimmed.
+        // On non Windows platforms, the full type is trimmed, unless it's Browser where we use FastInvariant for lazy ICU loading
         else if (globalizationMode is not null)
         {
-            Console.WriteLine("It is expected to have System.Globalization.GlobalizationMode type trimmed in non-Windows platforms");
+            Console.WriteLine("It is expected to have System.Globalization.GlobalizationMode type trimmed in non-Windows and non-Browser platforms");
             return -5;
         }
 

src/mono/browser/runtime/assets.ts

@@ -4,7 +4,7 @@
 import type { AssetEntryInternal } from "./types/internal";
 
 import cwraps from "./cwraps";
-import { mono_wasm_load_icu_data } from "./icu";
+import { mono_wasm_prepare_icu_data } from "./icu";
 import { Module, loaderHelpers, mono_assert, runtimeHelpers } from "./globals";
 import { mono_log_info, mono_log_debug, parseSymbolMapFile } from "./logging";
 import { mono_wasm_load_bytes_into_heap_persistent } from "./memory";
@@ -85,8 +85,7 @@ export function instantiate_asset (asset: AssetEntry, url: string, bytes: Uint8A
     } else if (asset.behavior === "pdb") {
         cwraps.mono_wasm_add_assembly(virtualName, offset!, bytes.length);
     } else if (asset.behavior === "icu") {
-        if (!mono_wasm_load_icu_data(offset!))
-            Module.err(`Error loading ICU asset ${asset.name}`);
+        mono_wasm_prepare_icu_data(offset!);
     } else if (asset.behavior === "resource") {
         cwraps.mono_wasm_add_satellite_assembly(virtualName, asset.culture || "", offset!, bytes.length);
     }

src/mono/browser/runtime/icu.ts

@@ -4,8 +4,19 @@
 import cwraps from "./cwraps";
 import { VoidPtr } from "./types/emscripten";
 
+
+let icuDataOffset: VoidPtr | null = null;
 // @offset must be the address of an ICU data archive in the native heap.
 // returns true on success.
-export function mono_wasm_load_icu_data (offset: VoidPtr): boolean {
-    return (cwraps.mono_wasm_load_icu_data(offset)) === 1;
+export function mono_wasm_prepare_icu_data (offset: VoidPtr) {
+    icuDataOffset = offset;
+}
+
+export function mono_wasm_load_icu_data () {
+    if (icuDataOffset === null) {
+        return;
+    }
+    if (!cwraps.mono_wasm_load_icu_data(icuDataOffset!)) {
+        throw new Error("Failed to load ICU data");
+    }
 }

src/mono/browser/runtime/startup.ts

@@ -34,6 +34,7 @@ import { runtimeList } from "./exports";
 import { nativeAbort, nativeExit } from "./run";
 import { mono_wasm_init_diagnostics } from "./diagnostics";
 import { replaceEmscriptenPThreadInit } from "./pthreads/worker-thread";
+import { mono_wasm_load_icu_data } from "./icu";
 
 export async function configureRuntimeStartup (module: DotnetModuleInternal): Promise<void> {
     if (!module.out) {
@@ -307,6 +308,8 @@ async function onRuntimeInitializedAsync (userOnRuntimeInitialized: () => void)
             await start_runtime();
         }
 
+        mono_wasm_load_icu_data();
+
         if (WasmEnableThreads) {
             await runtimeHelpers.afterIOStarted.promise;
         }