new trimmer feature System.TimeZoneInfo.Invariant

docs/design/features/timezone-invariant-mode.md

@@ -8,9 +8,28 @@ Therefore dotnet bundles the timezone database as binary as part of the runtime.
 That makes download size larger and application startup slower.
 If your application doesn't need to work with time zone information, you could use this feature to make the runtime about 200KB smaller.
 
-You enable it in project file:
+## Enabling the invariant mode
+
+Applications can enable the invariant mode by either of the following:
+
+1. in project file:
+
     ```xml
     <PropertyGroup>
         <InvariantTimezone>true</InvariantTimezone>
     </PropertyGroup>
     ```
+
+2. in `runtimeconfig.json` file:
+
+    ```json
+    {
+        "runtimeOptions": {
+            "configProperties": {
+                "System.TimeZoneInfo.Invariant": true
+            }
+        }
+    }
+    ```
+
+3. setting environment variable value `DOTNET_SYSTEM_TIMEZONE_INVARIANT` to `true` or `1`.

eng/testing/linker/project.csproj.template

@@ -76,6 +76,7 @@
   <Target Name="RemoveInvariantGlobalization" BeforeTargets="_SetWasmBuildNativeDefaults" Condition="'$(TargetArchitecture)' == 'wasm'">
     <ItemGroup>
       <_PropertiesThatTriggerRelinking Remove="InvariantGlobalization" />
+      <_PropertiesThatTriggerRelinking Remove="InvariantTimezone" />
     </ItemGroup>
   </Target>
 

src/installer/pkg/sfx/Microsoft.NETCore.App/Directory.Build.props

@@ -253,7 +253,6 @@
     <PlatformManifestFileEntry Include="wasi-link.rsp" IsNative="true" />
     <PlatformManifestFileEntry Include="ILLink.Substitutions.WasmIntrinsics.xml" IsNative="true" />
     <PlatformManifestFileEntry Include="ILLink.Substitutions.NoWasmIntrinsics.xml" IsNative="true" />
-    <PlatformManifestFileEntry Include="ILLink.Substitutions.LegacyJsInterop.xml" IsNative="true" />
     <!-- wasi specific -->
     <PlatformManifestFileEntry Include="main.c" IsNative="true" />
     <PlatformManifestFileEntry Include="driver.h" IsNative="true" />

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.FullGlobalizationData.cs

@@ -13,7 +13,8 @@ private static unsafe bool TryConvertIanaIdToWindowsId(string ianaId, bool alloc
             windowsId = null;
             return false;
 #else
-            if (GlobalizationMode.Invariant ||
+            if (Invariant ||
+                GlobalizationMode.Invariant ||
                 GlobalizationMode.UseNls ||
                 ianaId is null ||
                 ianaId.AsSpan().ContainsAny('\\', '\n', '\r')) // ICU uses these characters as a separator

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Unix.Android.cs

@@ -128,6 +128,8 @@ private static int ParseGMTNumericZone(string name)
         // Defaults to Utc if local time zone cannot be found
         private static TimeZoneInfo GetLocalTimeZoneCore()
         {
+            if (Invariant) return Utc;
+
             string? id = Interop.Sys.GetDefaultTimeZone();
             if (!string.IsNullOrEmpty(id))
             {
@@ -144,6 +146,7 @@ private static TimeZoneInfo GetLocalTimeZoneCore()
 
         private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachineCore(string id, out TimeZoneInfo? value, out Exception? e)
         {
+            Debug.Assert(!Invariant);
 
             value = id == LocalId ? GetLocalTimeZoneCore() : GetTimeZone(id, id);
 
@@ -441,6 +444,11 @@ private void LoadEntryAt(Stream fs, long position, out string id, out int byteOf
 
             public string[] GetTimeZoneIds()
             {
+                if (Invariant)
+                {
+                    return new string[] { "UTC" };
+                }
+
                 int numTimeZoneIDs = _isBackwards.AsSpan(0, _ids.Length).Count(false);
                 string[] nonBackwardsTZIDs = new string[numTimeZoneIDs];
                 var index = 0;

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Unix.NonAndroid.cs

@@ -3,6 +3,7 @@
 
 using System.Buffers;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Runtime.InteropServices;
@@ -25,6 +26,8 @@ public sealed partial class TimeZoneInfo
 
         private static TimeZoneInfo GetLocalTimeZoneCore()
         {
+            if (Invariant) return Utc;
+
             // Without Registry support, create the TimeZoneInfo from a TZ file
             return GetLocalTimeZoneFromTzFile();
         }
@@ -69,6 +72,8 @@ private static bool IdContainsAnyDisallowedChars(string zoneId)
 
         private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachineCore(string id, out TimeZoneInfo? value, out Exception? e)
         {
+            Debug.Assert(!Invariant);
+
             value = null;
             e = null;
 
@@ -147,6 +152,11 @@ private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachineCore(string id,
         /// </remarks>
         private static IEnumerable<string> GetTimeZoneIds()
         {
+            if (Invariant)
+            {
+                return new string[] { "UTC" };
+            }
+
             try
             {
                 var fileName = Path.Combine(GetTimeZoneDirectory(), TimeZoneFileName);
@@ -403,6 +413,8 @@ private static bool CompareTimeZoneFile(string filePath, byte[] buffer, byte[] r
         /// </summary>
         private static string FindTimeZoneId(byte[] rawData)
         {
+            Debug.Assert(!Invariant);
+
             // default to "Local" if we can't find the right tzfile
             string id = LocalId;
             string timeZoneDirectory = GetTimeZoneDirectory();
@@ -443,6 +455,8 @@ private static string FindTimeZoneId(byte[] rawData)
 
         private static bool TryLoadTzFile(string tzFilePath, [NotNullWhen(true)] ref byte[]? rawData, [NotNullWhen(true)] ref string? id)
         {
+            Debug.Assert(!Invariant);
+
             if (File.Exists(tzFilePath))
             {
                 try
@@ -469,6 +483,8 @@ private static bool TryLoadTzFile(string tzFilePath, [NotNullWhen(true)] ref byt
 #if TARGET_WASI || TARGET_BROWSER
         private static bool TryLoadEmbeddedTzFile(string name, [NotNullWhen(true)] out byte[]? rawData)
         {
+            Debug.Assert(!Invariant);
+
             IntPtr bytes = Interop.Sys.GetTimeZoneData(name, out int length);
             if (bytes == IntPtr.Zero)
             {
@@ -502,8 +518,11 @@ private static bool TryLoadEmbeddedTzFile(string name, [NotNullWhen(true)] out b
         /// </summary>
         private static bool TryGetLocalTzFile([NotNullWhen(true)] out byte[]? rawData, [NotNullWhen(true)] out string? id)
         {
+            Debug.Assert(!Invariant);
+
             rawData = null;
             id = null;
+
             string? tzVariable = GetTzEnvironmentVariable();
 
             // If the env var is null, on iOS/tvOS, grab the default tz from the device.
@@ -573,6 +592,8 @@ private static bool TryGetLocalTzFile([NotNullWhen(true)] out byte[]? rawData, [
         /// </summary>
         private static TimeZoneInfo GetLocalTimeZoneFromTzFile()
         {
+            Debug.Assert(!Invariant);
+
             byte[]? rawData;
             string? id;
             if (TryGetLocalTzFile(out rawData, out id))

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Unix.cs

@@ -288,6 +288,16 @@ private static void PopulateAllSystemTimeZones(CachedData cachedData)
         {
             Debug.Assert(Monitor.IsEntered(cachedData));
 
+            cachedData._systemTimeZones ??= new Dictionary<string, TimeZoneInfo>(StringComparer.OrdinalIgnoreCase)
+            {
+                { UtcId, s_utcTimeZone }
+            };
+
+            if (Invariant)
+            {
+                return;
+            }
+
             foreach (string timeZoneId in GetTimeZoneIds())
             {
                 TryGetTimeZone(timeZoneId, false, out _, out _, cachedData, alwaysFallbackToLocalMachine: true);  // populate the cache

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Win32.cs

@@ -114,6 +114,16 @@ private static void PopulateAllSystemTimeZones(CachedData cachedData)
         {
             Debug.Assert(Monitor.IsEntered(cachedData));
 
+            cachedData._systemTimeZones ??= new Dictionary<string, TimeZoneInfo>(StringComparer.OrdinalIgnoreCase)
+            {
+                { UtcId, s_utcTimeZone }
+            };
+
+            if (Invariant)
+            {
+                return;
+            }
+
             using (RegistryKey? reg = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive, writable: false))
             {
                 if (reg != null)
@@ -145,7 +155,7 @@ private TimeZoneInfo(in TIME_ZONE_INFORMATION zone, bool dstDisabled)
             }
             _baseUtcOffset = new TimeSpan(0, -(zone.Bias), 0);
 
-            if (!dstDisabled)
+            if (!Invariant && !dstDisabled)
             {
                 // only create the adjustment rule if DST is enabled
                 REG_TZI_FORMAT regZone = new REG_TZI_FORMAT(zone);
@@ -230,6 +240,8 @@ private static bool CheckDaylightSavingTimeNotSupported(in TIME_ZONE_INFORMATION
         /// </summary>
         private static string? FindIdFromTimeZoneInformation(in TIME_ZONE_INFORMATION timeZone, out bool dstDisabled)
         {
+            Debug.Assert(!Invariant);
+
             dstDisabled = false;
 
             using (RegistryKey? key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive, writable: false))
@@ -261,6 +273,11 @@ private static TimeZoneInfo GetLocalTimeZone(CachedData cachedData)
         {
             Debug.Assert(Monitor.IsEntered(cachedData));
 
+            if (Invariant)
+            {
+                return Utc;
+            }
+
             //
             // Try using the "kernel32!GetDynamicTimeZoneInformation" API to get the "id"
             //
@@ -347,6 +364,12 @@ private static TimeZoneInfoResult TryGetTimeZone(string id, out TimeZoneInfo? ti
         internal static TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out bool isAmbiguousLocalDst)
         {
             isAmbiguousLocalDst = false;
+
+            if (Invariant)
+            {
+                return TimeSpan.Zero;
+            }
+
             int timeYear = time.Year;
 
             OffsetAndRule match = s_cachedData.GetOneYearLocalFromUtc(timeYear);
@@ -490,6 +513,8 @@ private static bool TransitionTimeFromTimeZoneInformation(in REG_TZI_FORMAT time
         /// </summary>
         private static bool TryCreateAdjustmentRules(string id, in REG_TZI_FORMAT defaultTimeZoneInformation, out AdjustmentRule[]? rules, out Exception? e, int defaultBaseUtcOffset)
         {
+            Debug.Assert(!Invariant);
+
             rules = null;
             e = null;
 
@@ -720,7 +745,7 @@ private static bool TryCompareTimeZoneInformationToRegistry(in TIME_ZONE_INFORMA
         /// </summary>
         private static string GetLocalizedNameByMuiNativeResource(string resource)
         {
-            if (string.IsNullOrEmpty(resource) || (GlobalizationMode.Invariant && GlobalizationMode.PredefinedCulturesOnly))
+            if (string.IsNullOrEmpty(resource) || Invariant || (GlobalizationMode.Invariant && GlobalizationMode.PredefinedCulturesOnly))
             {
                 return string.Empty;
             }
@@ -785,6 +810,8 @@ private static string GetLocalizedNameByMuiNativeResource(string resource)
         /// </summary>
         private static unsafe string GetLocalizedNameByNativeResource(string filePath, int resource)
         {
+            Debug.Assert(!Invariant);
+
             IntPtr handle = IntPtr.Zero;
             try
             {
@@ -821,6 +848,8 @@ private static unsafe string GetLocalizedNameByNativeResource(string filePath, i
         /// </summary>
         private static void GetLocalizedNamesByRegistryKey(RegistryKey key, out string? displayName, out string? standardName, out string? daylightName)
         {
+            Debug.Assert(!Invariant);
+
             displayName = string.Empty;
             standardName = string.Empty;
             daylightName = string.Empty;
@@ -867,6 +896,8 @@ private static void GetLocalizedNamesByRegistryKey(RegistryKey key, out string?
         /// </summary>
         private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out TimeZoneInfo? value, out Exception? e)
         {
+            Debug.Assert(!Invariant);
+
             e = null;
 
             // Standard Time Zone Registry Data
@@ -950,6 +981,11 @@ private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out
         // Helper function to get the standard display name for the UTC static time zone instance
         private static string GetUtcStandardDisplayName()
         {
+            if (Invariant)
+            {
+                return InvariantUtcStandardDisplayName;
+            }
+
             // Don't bother looking up the name for invariant or English cultures
             CultureInfo uiCulture = CultureInfo.CurrentUICulture;
             if (uiCulture.Name.Length == 0 || uiCulture.TwoLetterISOLanguageName == "en")

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.cs

@@ -60,6 +60,9 @@ private enum TimeZoneInfoResult
         private static readonly TimeZoneInfo s_utcTimeZone = CreateUtcTimeZone();
         private static CachedData s_cachedData = new CachedData();
 
+        [FeatureSwitchDefinition("System.TimeZoneInfo.Invariant")]
+        internal static bool Invariant { get; } = AppContextConfigHelper.GetBooleanConfig("System.TimeZoneInfo.Invariant", "DOTNET_SYSTEM_TIMEZONE_INVARIANT");
+
         //
         // All cached data are encapsulated in a helper class to allow consistent view even when the data are refreshed using ClearCachedData()
         //
@@ -2054,6 +2057,12 @@ private static TimeZoneInfoResult TryGetTimeZoneUsingId(string id, bool dstDisab
             TimeZoneInfoResult result = TimeZoneInfoResult.Success;
             e = null;
 
+            if (Invariant && !cachedData._allSystemTimeZonesRead)
+            {
+                PopulateAllSystemTimeZones(cachedData);
+                cachedData._allSystemTimeZonesRead = true;
+            }
+
             // check the cache
             if (cachedData._systemTimeZones != null)
             {
@@ -2069,6 +2078,12 @@ private static TimeZoneInfoResult TryGetTimeZoneUsingId(string id, bool dstDisab
                 }
             }
 
+            if (Invariant)
+            {
+                value = null;
+                return TimeZoneInfoResult.TimeZoneNotFoundException;
+            }
+
             if (cachedData._timeZonesUsingAlternativeIds != null)
             {
                 if (cachedData._timeZonesUsingAlternativeIds.TryGetValue(id, out value))
@@ -2105,6 +2120,8 @@ private static TimeZoneInfoResult TryGetTimeZoneUsingId(string id, bool dstDisab
 
         private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, bool dstDisabled, out TimeZoneInfo? value, out Exception? e, CachedData cachedData)
         {
+            Debug.Assert(!Invariant);
+
             TimeZoneInfoResult result;
 
             result = TryGetTimeZoneFromLocalMachine(id, out value, out e);

src/libraries/System.Runtime/tests/System.Runtime.Tests/Hybrid/System.Runtime.IOS.Tests.csproj

@@ -13,6 +13,7 @@
 
   <ItemGroup>
     <Compile Include="..\System\TimeZoneInfoTests.cs" />
+    <Compile Include="..\System\TimeZoneInfoTests.Common.cs" />
     <Compile Include="..\System\TimeZoneTests.cs" />
     <Compile Include="..\System\TimeZoneNotFoundExceptionTests.cs" />
     <Compile Include="..\System\Text\StringBuilderTests.cs" />

src/libraries/System.Runtime/tests/System.Runtime.Tests/InvariantTimezone/System.Runtime.InvariantTimezone.Tests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <TestRuntime>true</TestRuntime>
+    <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
+    <InvariantTimezone>true</InvariantTimezone>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <WithoutCategories>$(WithoutCategories);AdditionalTimezoneChecks</WithoutCategories>
+  </PropertyGroup>
+
+  <ItemGroup>
+
+    <!-- can be removed after https://github.com/dotnet/sdk/pull/45792/ -->
+    <RuntimeHostConfigurationOption Include="System.TimeZoneInfo.Invariant"
+                                        Condition="'$(InvariantTimezone)' != ''"
+                                        Value="$(InvariantTimezone)"
+                                        Trim="true" />
+
+    <Compile Include="..\System\TimeZoneInfoTests.Common.cs" />
+    <Compile Include="..\System\TimeZoneInfoTests.Invariant.cs" />
+    <Compile Include="..\System\TimeZoneTests.cs" />
+    <Compile Include="..\System\TimeZoneNotFoundExceptionTests.cs" />
+  </ItemGroup>
+</Project>

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

@@ -168,6 +168,7 @@
     <Compile Include="System\TimeoutExceptionTests.cs" />
     <Compile Include="System\TimeSpanTests.cs" />
     <Compile Include="System\TimeZoneInfoTests.cs" />
+    <Compile Include="System\TimeZoneInfoTests.Common.cs" />
     <Compile Include="System\TimeZoneTests.cs" />
     <Compile Include="System\TimeZoneNotFoundExceptionTests.cs" />
     <Compile Include="System\TypedReferenceTests.cs" />