new trimmer feature System.TimeZoneInfo.Invariant #111215

pavelsavara · 2025-01-08T21:02:14Z

Motivation: when TryGetLocalTzFile is included it brings dependency to System.IO.File and its dependencies.

new trimmer feature System.TimeZoneInfo.Invariant triggered by existing <InvariantTimezone>true</InvariantTimezone>
- breaking change: it will prevent loading TZ info files from FS
new System.TimeZoneInfo.Invariant getter also driven by DOTNET_SYSTEM_TIMEZONE_INVARIANT env variable
cleanup ILLink.Substitutions.LegacyJsInterop.xml

<InvariantTimezone>true</InvariantTimezone> is pre-existing feature.

After discussion below the implementation was unified to other platforms.
Explanation of the feature in comment below.

dotnet-policy-service · 2025-01-08T21:02:48Z

Tagging subscribers to this area: @dotnet/area-system-globalization
See info in area-owners.md if you want to be subscribed.

tarekgh · 2025-01-08T21:32:00Z

Will it be acceptable to have DateTime.Now report wrong time when the invariant mode is enabled?

pavelsavara · 2025-01-08T21:56:42Z

Will it be acceptable to have DateTime.Now report wrong time when the invariant mode is enabled?

It will report UTC. Also this behavior already existed before this PR, here I'm just removing the ability to load TZ data from file system, when InvariantTimezone is true.

tarekgh · 2025-01-08T22:42:05Z

It will report UTC. Also this behavior already existed before this PR, here I'm just removing the ability to load TZ data from file system, when InvariantTimezone is true.

Thanks. I am not sure my question is answered :-) I am not questioning the PR more than questioning behavior. I guess users haven't run into this yet to report it. Returning UTC time when having TZ settings different than UTC is questionable. Maybe it is acceptable to the browser (especially servers) but wanted to know how we validated this assumption.
Maybe the explicit opt-in switch introduced here is better as users will explicitly enable and understand the consequences.

src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets

pavelsavara · 2025-01-09T11:25:33Z

Returning UTC time when having TZ settings different than UTC is questionable.

This is not how it works. You would not be able to change to non-UTC timezone. Let me show you:

given code

Console.WriteLine($"TimeZoneInfo.Local is {TimeZoneInfo.Local}");
Console.WriteLine($"DateTime.UtcNow is {DateTime.UtcNow}");
Console.WriteLine($"DateTime.Now is {DateTime.Now}");
var start = DateTime.UtcNow;
var timezonesCount = TimeZoneInfo.GetSystemTimeZones().Count;
await Delay(100);
var end = DateTime.UtcNow;
Console.WriteLine($"Found {timezonesCount} timezones in the TZ database in {end - start}");

TimeZoneInfo utc = TimeZoneInfo.FindSystemTimeZoneById("UTC");
Console.WriteLine($"{utc.DisplayName} BaseUtcOffset is {utc.BaseUtcOffset}");

try
{
    TimeZoneInfo tst = TimeZoneInfo.FindSystemTimeZoneById("Asia/Tokyo");
    Console.WriteLine($"{tst.DisplayName} BaseUtcOffset is {tst.BaseUtcOffset}");
}
catch (TimeZoneNotFoundException tznfe)
{
    Console.WriteLine($"Could not find Asia/Tokyo: {tznfe.Message}");
}

At 12:19 in Prague, you will get following output

TimeZoneInfo.Local is (UTC) UTC
DateTime.UtcNow is 1/9/2025 11:19:52 AM
DateTime.Now is 1/9/2025 11:19:52 AM
Found 0 timezones in the TZ database in 00:00:00.1200000
(UTC) UTC BaseUtcOffset is 00:00:00
Could not find Asia/Tokyo: The time zone ID 'Asia/Tokyo' was not found on the local computer.

pavelsavara · 2025-01-09T11:37:44Z

The <InvariantTimezone>true</InvariantTimezone> feature is opt-in and it means: "I don't care for timezones, please make the application as small as possible".

On the browser "operating system" we don't have TZ database pre-installed and so we are bundling it with each application. It's 300KB of download and some CPU time before the runtime can start. That's a lot for a web app, especially if your business logic is not about dates/times/calendars.

Before this PR the <InvariantTimezone>true</InvariantTimezone> would just stop shipping the data. But you would be able to ship your own and store it into emscripten virtual file system yourself. There are probably nobody in the world that knew this was possible.

I feel quite safe to make this change for the browser target.

@steveisok is this how it works for iOS too ?

Can I assume people are not shipping custom TZDIR there at the same time when they set <InvariantTimezone>true</InvariantTimezone> ?

steveisok · 2025-01-09T14:23:11Z

@steveisok is this how it works for iOS too ?

We don't ship anything custom on iOS or Android as we rely on whatever they do.

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

- add new System.Runtime.InvariantTimezone.Tests.csproj

src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Substitutions.Shared.xml

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

Co-authored-by: Sven Boemer <sbomer@gmail.com>

# Conflicts: # src/libraries/System.Runtime/tests/System.Runtime.Tests/System/TimeZoneInfoTests.cs

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

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

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

…in32.cs Co-authored-by: Alexander Köplinger <alex.koeplinger@outlook.com>

…nix.NonAndroid.cs Co-authored-by: Alexander Köplinger <alex.koeplinger@outlook.com>

pavelsavara · 2025-01-23T12:44:05Z

@sbomer @MichalStrehovsky @tarekgh do you have further questions or feedback ?

tarekgh · 2025-01-23T16:38:51Z

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

+                value = null;
+                e = new TimeZoneNotFoundException(SR.Format(SR.InvalidTimeZone_InvalidId, id));
+                return TimeZoneInfoResult.TimeZoneNotFoundException;
+            }



We should add assert here that never reach this code when Invariant is true.

tarekgh · 2025-01-23T16:41:29Z

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

+            cachedData._systemTimeZones ??= new Dictionary<string, TimeZoneInfo>(StringComparer.OrdinalIgnoreCase)
+            {
+                { UtcId, s_utcTimeZone }
+            };


should this get moved inside the Invariant block?

Could the UTC get enumerated again in GetTimeZoneIds()?

tarekgh · 2025-01-23T16:43:20Z

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

@@ -72,6 +72,11 @@ private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachineCore(string id,
            value = null;
            e = null;

+            if (Invariant)
+            {


should assert here not having Invariant is true?

tarekgh · 2025-01-23T16:47:50Z

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

@@ -403,6 +413,11 @@ private static bool CompareTimeZoneFile(string filePath, byte[] buffer, byte[] r
        /// </summary>
        private static string FindTimeZoneId(byte[] rawData)
        {
+            if (Invariant)


Invariant

Is it possible to reach here when Invariant is true? I think if not, we should assert in all such places.

tarekgh · 2025-01-23T16:51:16Z

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

+            {
+                { UtcId, s_utcTimeZone }
+            };
+


move inside Invariant block?

tarekgh

Thanks @pavelsavara
I added a few minor comments. LGTM otherwise

sbomer

LGTM, thank you!

MichalStrehovsky · 2025-01-23T21:53:49Z

...e/tests/System.Runtime.Tests/InvariantTimezone/System.Runtime.InvariantTimezone.Tests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos</TargetFrameworks>


Can this be <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>?

Is there a platform where we don't respect this? If so, why?

pavelsavara added arch-wasm WebAssembly architecture area-System.Globalization size-reduction Issues impacting final app size primary for size sensitive workloads labels Jan 8, 2025

pavelsavara added this to the 10.0.0 milestone Jan 8, 2025

pavelsavara self-assigned this Jan 8, 2025

pavelsavara mentioned this pull request Jan 8, 2025

linker feature System.TimeZoneInfo.Invariant dotnet/sdk#45792

Merged

pavelsavara requested a review from ilonatommy January 8, 2025 22:12

This was referenced Jan 9, 2025

System.Runtime.Tests.WorkItemExecution "crash" on tvOS #106319

Open

restarted. Azure DevOps can't recover from restarts. dotnet/dnceng#3879

Open

ModuleNotFoundError: No module named 'pkg_resources' dotnet/dnceng#4756

Open

MichalStrehovsky reviewed Jan 9, 2025

View reviewed changes

src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets Outdated Show resolved Hide resolved

pavelsavara marked this pull request as ready for review January 9, 2025 13:16

pavelsavara requested review from sbomer, lewing, steveisok and vitek-karas as code owners January 9, 2025 13:16

pavelsavara requested review from steveisok and removed request for steveisok January 9, 2025 13:16

pavelsavara mentioned this pull request Jan 9, 2025

[Mono] trim hot reload #111247

Merged

rebase and move MetadataUpdaterSupport changes to different PR

48ccc77

pavelsavara force-pushed the browser_trim_timezones branch from b5ce502 to 48ccc77 Compare January 9, 2025 17:37

pavelsavara changed the title ~~[browser] new trimmer feature System.TimeZoneInfo.Invariant~~ [WASM] new trimmer feature System.TimeZoneInfo.Invariant Jan 9, 2025

sbomer reviewed Jan 9, 2025

View reviewed changes

docs/design/features/timezone-invariant-mode.md Show resolved Hide resolved

pavelsavara added 2 commits January 20, 2025 17:26

- split TimeZoneInfoTests.Common.cs

5e98904

- add new System.Runtime.InvariantTimezone.Tests.csproj

tests

d5bc555

build-analysis bot mentioned this pull request Jan 20, 2025

The hosted runner encountered an error while running your job. (Error Type: Disconnect). dotnet/dnceng#1919

Open

3 tasks

fix tests

0a0b544

sbomer reviewed Jan 21, 2025

View reviewed changes

src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Substitutions.Shared.xml Outdated Show resolved Hide resolved

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.cs Show resolved Hide resolved

pavelsavara and others added 3 commits January 22, 2025 12:37

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

1825361

Co-authored-by: Sven Boemer <sbomer@gmail.com>

Merge branch 'main' into browser_trim_timezones

bfaa41e

# Conflicts: # src/libraries/System.Runtime/tests/System.Runtime.Tests/System/TimeZoneInfoTests.cs

feedback + fix merge

08deca6

build-analysis bot mentioned this pull request Jan 22, 2025

[WASI] Sockets - unknown handle index #108726

Open

akoeplinger reviewed Jan 22, 2025

View reviewed changes

pavelsavara and others added 4 commits January 23, 2025 11:09

Update src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.W…

416a2a2

…in32.cs Co-authored-by: Alexander Köplinger <alex.koeplinger@outlook.com>

Update src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.W…

706a550

…in32.cs Co-authored-by: Alexander Köplinger <alex.koeplinger@outlook.com>

Update src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.W…

358e1a1

…in32.cs Co-authored-by: Alexander Köplinger <alex.koeplinger@outlook.com>

Update src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.U…

01ba971

…nix.NonAndroid.cs Co-authored-by: Alexander Köplinger <alex.koeplinger@outlook.com>

pavelsavara changed the title ~~[WASM] new trimmer feature System.TimeZoneInfo.Invariant~~ new trimmer feature System.TimeZoneInfo.Invariant Jan 23, 2025

pavelsavara removed the arch-wasm WebAssembly architecture label Jan 23, 2025

akoeplinger approved these changes Jan 23, 2025

View reviewed changes

This was referenced Jan 23, 2025

[wasm][mt] fail: System.TypeLoadException: Could not load type of field" #102615

Open

System.Net.Quic tests timeout #107761

Open

tarekgh reviewed Jan 23, 2025

View reviewed changes

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

{

{ UtcId, s_utcTimeZone }

};

Copy link

Member

tarekgh Jan 23, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

move inside Invariant block?

tarekgh approved these changes Jan 23, 2025

View reviewed changes

sbomer approved these changes Jan 23, 2025

View reviewed changes

MichalStrehovsky approved these changes Jan 23, 2025

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

new trimmer feature System.TimeZoneInfo.Invariant #111215

new trimmer feature System.TimeZoneInfo.Invariant #111215

pavelsavara commented Jan 8, 2025 •

edited

Loading

dotnet-policy-service bot commented Jan 8, 2025

tarekgh commented Jan 8, 2025

pavelsavara commented Jan 8, 2025

tarekgh commented Jan 8, 2025 •

edited

Loading

pavelsavara commented Jan 9, 2025

pavelsavara commented Jan 9, 2025

steveisok commented Jan 9, 2025

pavelsavara commented Jan 23, 2025

tarekgh Jan 23, 2025

tarekgh Jan 23, 2025

tarekgh Jan 23, 2025

tarekgh Jan 23, 2025

tarekgh Jan 23, 2025

tarekgh left a comment

sbomer left a comment

MichalStrehovsky Jan 23, 2025

new trimmer feature System.TimeZoneInfo.Invariant #111215

Are you sure you want to change the base?

new trimmer feature System.TimeZoneInfo.Invariant #111215

Conversation

pavelsavara commented Jan 8, 2025 • edited Loading

dotnet-policy-service bot commented Jan 8, 2025

tarekgh commented Jan 8, 2025

pavelsavara commented Jan 8, 2025

tarekgh commented Jan 8, 2025 • edited Loading

pavelsavara commented Jan 9, 2025

pavelsavara commented Jan 9, 2025

steveisok commented Jan 9, 2025

pavelsavara commented Jan 23, 2025

tarekgh Jan 23, 2025

Choose a reason for hiding this comment

tarekgh Jan 23, 2025

Choose a reason for hiding this comment

tarekgh Jan 23, 2025

Choose a reason for hiding this comment

tarekgh Jan 23, 2025

Choose a reason for hiding this comment

tarekgh Jan 23, 2025

Choose a reason for hiding this comment

tarekgh left a comment

Choose a reason for hiding this comment

sbomer left a comment

Choose a reason for hiding this comment

MichalStrehovsky Jan 23, 2025

Choose a reason for hiding this comment

pavelsavara commented Jan 8, 2025 •

edited

Loading

tarekgh commented Jan 8, 2025 •

edited

Loading