FF-3753 feat(dart): Dart SDK #197

rasendubi · 2025-02-05T17:43:22Z

No description provided.

Copied flutter_rust_bridge minimal example[1] and beat it into working: - vendored simple_build.dart to remove dependency on an unpublished git-only package - updated packages because I couldn't get dart test to work otherwise - stripped flutter_rust_bridge internal options [1]: https://github.com/fzyzcjy/flutter_rust_bridge/tree/05247dd90a7fcb2512c5ede13cf00271b0eb548e/frb_example/dart_minimal

changeset-bot · 2025-02-05T17:43:26Z

🦋 Changeset detected

Latest commit: 69fdcb2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
eppo_core	Major
python-sdk	Minor
ruby-sdk	Minor
rust-sdk	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

Dropping `BackgroundRuntime` cancels all tracked tasks. This may (and have) lead to hard to debug issues when configuration poller just stops working and `.wait_for_configuration()` unhelpfully returns `PollerThreadPanicked`. (I am a little embarrassed to say how long this simple issue took me to debug when it was paired with running in Dart environment.)

rasendubi · 2025-02-17T21:11:51Z

I'm going to work on adding documentation next but this is now ready for review 🎉

schmit · 2025-02-19T06:34:51Z

dart-sdk/lib/src/client.dart

+    await this._core!.waitForInitialization();
+  }
+
+  String stringAssignment(String flagKey, Subject subject, String defaultValue) {


Just wanted to note that this is a different signature than usual, with a subject instead of subjectId and subjectAttributes

Yeah, the ask for review leaked slightly earlier than I expected, so I didn't have the time to annotate all the interesting parts 🙂

For the difference here: I hate Attributes/ContextAttributes distinction in other SDKs, so I tried to experiment with it. This change makes signature uniform for both assignments and bandits.

Bandit signature for comparison (no ContextAttributes!):

EvaluationResult<String> banditAction( String flagKey, Subject subject, Map<String, Attributes> actions, String defaultVariation)

and example usage in Dart (from test):

final bandit = client.banditAction( 'banner_bandit_flag', Subject('alice') ..numberAttribute('age', 25) ..stringAttribute('country', 'USA') ..stringAttribute('genderIdentity', 'female'), { 'nike': Attributes() ..numberAttribute('brand_affinity', 1.0) ..stringAttribute('loyalty_tier', 'gold') ..boolAttribute('purchased_last_30_days', true), }, 'control', );

That seems to work better for typed languages that don't allow mixing strings and numbers in the same container. I like it but curious what other think.

schmit · 2025-02-19T06:41:41Z

eppo_core/src/background/runtime.rs

@@ -101,6 +101,7 @@ impl BackgroundRuntime {

    /// Command background activities to stop and exit.
    pub(crate) fn stop(&self) {
+        log::debug!(target: "eppo", "stopping background runtime");


Did you intend to keep this debug here?

Absolutely: 5353290

I've spent a couple of days debugging why poller mysteriously crashes (spoiler: it was just background runtime silently stopping). That log line would cut the debugging to one minute 🙈

schmit · 2025-02-19T06:42:35Z

As a first-time Dart user, this looks very clean and insightful! Will be prudent and have a second pair of eyes approve

leoromanovsky

@rasendubi this is huge - I did a line by line review and enjoying reading all of it. I can tell you had to solve several challenges related to the background runtime across wasm/non-wasm as well as running in the javascript environment. Very appreciated that you didn't take shortcuts but seemed to step back and create generalized interfaces for the new behavior.

Before approving and releasing could you please help me run the dart & flutter web artifacts locally so I can get comfort with the tooling? Apologize for not figuring this out myself after some research.

leoromanovsky · 2025-02-22T07:07:53Z

.changeset/giant-eyes-tie.md

+
+Make async runtime abstract.
+
+This introduces an `AsyncRuntime` trait that allows us to abstract over different async runtimes. This is required to support Dart SDK that doesn't use tokio runtime in web build.


Wow, very nice!

we probably need to add a note here about dropping openssl in favor of rust-tls

@felipecsl I've added another changeset for this. This one affects all SDKs though

leoromanovsky · 2025-02-22T16:12:05Z

package.json

@@ -8,6 +8,7 @@
    "test:rust": "cargo test",
    "test:python": "cd python-sdk && pytest",
    "test:ruby": "cd ruby-sdk && bundle exec rake build && bundle exec rspec",
+    "test:dart": "cd dart-sdk && dart --enable-experiment=native-assets test",


Tried running this locally with exception:

Compiling eppo_dart v1.0.0 (/Users/leo/src/eppo-multiplatform/dart-sdk/rust) error: failed to run custom build command for `eppo_dart v1.0.0 (/Users/leo/src/eppo-multiplatform/dart-sdk/rust)` Caused by: process didn't exit successfully: `/Users/leo/src/eppo-multiplatform/dart-sdk/rust/target/release/build/eppo_dart-6f7c55cf4f81c058/build-script-build` (exit status: 101) --- stdout [2025-02-22T16:06:52.693Z DEBUG /Users/leo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/flutter_rust_bridge_codegen-2.8.0/src/library/codegen/config/config_parser.rs:51] Found config file ../flutter_rust_bridge.yaml [2025-02-22T16:06:52.694Z DEBUG /Users/leo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/flutter_rust_bridge_codegen-2.8.0/src/library/codegen/mod.rs:23] config=Config { base_dir: Some(".."), rust_input: Some("crate::api"), dart_output: Some("lib/src/rust"), c_output: Some("frb_generated.h"), duplicated_c_output: None, rust_root: None, rust_output: None, dart_entrypoint_class_name: None, dart_format_line_length: None, dart_preamble: None, rust_preamble: Some("use eppo_core::{Str, AttributeValue};\n"), dart_enums_style: None, add_mod_to_lib: None, llvm_path: None, llvm_compiler_opts: None, dart_root: None, build_runner: None, extra_headers: None, web: None, deps_check: None, dart3: None, full_dep: None, local: None, default_external_library_loader_web_prefix: None, dart_type_rename: None, enable_lifetime: None, type_64bit_int: None, default_dart_async: Some(false), stop_on_error: None, dump: None, dump_all: None, rust_features: None } meta_config=MetaConfig { watch: false } [2025-02-22T16:06:52.695Z DEBUG /Users/leo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/flutter_rust_bridge_codegen-2.8.0/src/library/codegen/config/internal_config_parser/mod.rs:33] InternalConfig.parse base_dir="/Users/leo/src/eppo-multiplatform/dart-sdk" [2025-02-22T16:06:52.696Z ERROR /Users/leo/.cargo/registry/src/index.crates.io-6f17d22bba15001f/flutter_rust_bridge_codegen-2.8.0/src/library/utils/logs.rs:54] panicked at build.rs:25:6: called `Result::unwrap()` on an `Err` value: Fail to canonicalize path="/Users/leo/src/eppo-multiplatform/dart-sdk/lib/src/rust" Caused by: No such file or directory (os error 2) --- stderr thread 'main' panicked at build.rs:25:6: called `Result::unwrap()` on an `Err` value: Fail to canonicalize path="/Users/leo/src/eppo-multiplatform/dart-sdk/lib/src/rust" Caused by: No such file or directory (os error 2) note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace Unhandled exception: ProcessException: Bad exit code (101). If you want to see extra information, set FRB_DART_RUN_COMMAND_STDERR=1 Command: cargo build --release #0 runCommand (package:flutter_rust_bridge/src/cli/run_command.dart:67:5) <asynchronous suspension> #1 simpleBuild (file:///Users/leo/src/eppo-multiplatform/dart-sdk/simple_build.dart:54:5) <asynchronous suspension> stdout: Error: Compiling native assets failed.

do you expect this command to succeed on macos?

oh, it might be because you don't have lib/src/rust directory. It's auto-generated, so git-ignored. I've just added a .gitkeep file, so git will create a directory for you when you pull latest changes

leoromanovsky · 2025-02-22T16:14:01Z

eppo_core/src/background/runtime.rs

+    /// If you want your task to react to shutdown and perform some cleanup, spawn your task with
+    /// [`BackgroundThread::spawn_tracked()`] and watch this cancellation token.
+    ///
+    /// Note: this is a child token of the main cancellation token, so canceling it does not cancel


very nice - this will be primarily used within SDKs or can you imagine a customer facing use too?

I don't think there's customer use. Right now, this is only used within core (not even exported to individual sdks)

leoromanovsky · 2025-02-22T16:18:47Z

dart-sdk/rust/src/runtime.rs

+            .0
+             .0


If the underlying interfaces changes do you think the compiler will break here and alert us? Consider how to write this with protection and a log message to help a future developer.

Yes, absolutely. That's one of the things that broke in web build because implementation is different.

We are pinning rust_flutter_bridge version, so this should not break unexpectedly. And when it does, the error will be scoped to this file, so it will be quite clear what happened

leoromanovsky · 2025-02-22T16:23:42Z

eppo_core/src/background/async_runtime.rs

+/// `AsyncRuntime` abstracts over various Rust's async runtimes with minimal interface. This is
+/// usually just a tokio Handle but Dart SDK in wasm uses a custom implementation.


I did most of my reading around this change to understand it and got introduced to the Send interface, thanks! https://doc.rust-lang.org/nomicon/send-and-sync.html

Also needed help from AI to understand how it fit together with the wasm single threaded runtime.

In the future, if more non-Send futures need handling, you may need a more generalized solution (e.g., perhaps relax the trait bound for wasm via conditional compilation, or provide a separate method for non-Send tasks). For now, the approach is correct and contained to config polling.

What do you imagine doing down the line to evolve this interface?

Yeah, I don't really like this AsyncRuntime and I kinda used an escape hatch in configuration poller by invoking wasm spawn directly.

Having different definition for wasm is possible but it's going to be contagious as interfaces of spawn_tracked/_untracked would change as well. I don't think it's going to propagate much further though, so probably worth biting that bullet at some point.

I'm also not entirely sure what's multi-threading story for wasm is. It looks like there is some support for threading on some platforms and on web via SharedArrayBuffer (when cross-origin isolation is enabled).

dart-sdk/rust/src/api/client.rs

leoromanovsky · 2025-02-22T16:29:38Z

dart-sdk/rust/src/api/client.rs

+        flag_key: &str,
+        subject_key: Str,
+        subject_attributes: HashMap<Str, AttributeValue>,
+    ) -> (Option<Str>, Option<AssignmentEvent>) {


Is it easier to return this type instead of a Result for use in dart or did something else inform your decision?

Don't remember exactly but it's probably because we needed to convert from uni-typed AssignmentValue to Str, so ended up with this destructuring:

let Ok(Some(Assignment { value: AssignmentValue::String(result), event, })) = self.evaluator.get_assignment(...) else { return ...; };

at which point the two sensible options are either Option<(Str, Option<AssignmentEvent>)> (or Result outside) or (Option<Str>, Option<AssignmentEvent>). The first one is more faithful (because event can only be present if there's an assignment) but the second is slightly easier to work from Dart:

final (result, event) = core.stringAssignment(flagKey, subject.key, subject.attributes.coreAttributes); this.logAssignmentEvent(event); return result ?? defaultValue;

vs. having to unnest two levels of optionals

rasendubi · 2025-02-23T20:50:38Z

@leoromanovsky sharing my stashed commands for web build (my understanding is that we'll put them in CI before release):

prepare:
    cargo install -f flutter_rust_bridge_codegen@=2.8.0 wasm-pack wasm-bindgen-cli

build-web:
    flutter_rust_bridge_codegen build-web --wasm-pack-rustflags '--cfg getrandom_backend="wasm_js" -C target-feature=+atomics,+bulk-memory,+mutable-globals'

rasendubi · 2025-02-25T05:01:38Z

Another piece that I totally forgot to mention is that dart-sdk has its own cargo workspace, so for local testing we need to override eppo_core crate (similarly to how we do in ruby).

Put the following in dart-sdk/rust/.cargo/config.toml:

[patch.crates-io]
eppo_core = { path = '../../eppo_core' }

felipecsl · 2025-02-27T18:13:20Z

I can confirm I'm on dart 3.7 - will try downgrading to 3.6

Just to follow up here, I can confirm I was able to build for web with Dart 3.6

This is used as the name of js/wasm generated files.

* add plugin info * remove plugin details * vendor libs * remove corepack changes * add rust api files * add more generated code * add another missing file * catch reqwest panic * replace openssl with rustls-tls * update deps * remove native-tls and openssl * remove generated files * another file to remove * remove openssl-sys * newlines * revert this * keep vendored feature * try to fix python CI * set vars for linux gnu * install deps * another try * build with `cross` instead * fix cross commang * fix target platform triple * another try * revert action changes * another try - see PyO3/maturin-action#222 * once again * anotehr place

felipecsl · 2025-02-28T20:55:30Z

.changeset/giant-eyes-tie.md

+
+Make async runtime abstract.
+
+This introduces an `AsyncRuntime` trait that allows us to abstract over different async runtimes. This is required to support Dart SDK that doesn't use tokio runtime in web build.


we probably need to add a note here about dropping openssl in favor of rust-tls

felipecsl · 2025-02-28T20:56:40Z

dart-sdk/rust/build-android-aarch64.sh

+export AR_aarch64_linux_android="$NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin/llvm-ar"
+export RANLIB="$NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin/llvm-ranlib"
+
+cargo build --release --target aarch64-linux-android -p eppo_dart


we can probably drop this in favor of https://github.com/cross-rs/cross in the future

leoromanovsky · 2025-02-28T21:38:44Z

.changeset/giant-eyes-tie.md

@@ -0,0 +1,7 @@
+---
+"eppo_core": major


Thanks for making this a major bump - makes a ton of sense to give us room to test python and ruby more extensively.

It doesn't give us much room. It is going to bump eppo_core's version in both python and ruby, so the next python/ruby releases will release with this new change. (This is the same regardless of whether it's a major or patch change.)

This reduces wasm file from 12M down to 2M.

rasendubi · 2025-03-03T15:34:37Z

@felipecsl python build started to fail. Do you think it is related to the rustls changes?

felipecsl · 2025-03-03T17:57:36Z

@felipecsl python build started to fail. Do you think it is related to the rustls changes?

@rasendubi it was working on friday on my branch #222 and also started failing there, I think something changed in the underlying OS, taking a look

felipecsl · 2025-03-03T18:04:07Z

See PyO3/maturin-action#331

* chore(ci): dart-sdk rust cross compile for android target * eppo_dart instead of eppo_sdk * revert this * build patches * revert this * update file path for testing * another try * change working dir * CI tweaks * better logs * more fix attempts * aaaand another try * 10th time is the charm * check for path instead * check CI env var * passthrough env var * use the fork of maturin-action * yup * bump action version * fix step * fix ste * update action version, another shot at android fix * fix pytest * move file * add file * set rust root to current dir * fix cross build config * manually run codegen * install dart * reorder steps * another reorder * another try * go back to main maturin-action * remove custom build scripts * add android x86 * remove images cross config * go back to maturin-action v1

felipecsl · 2025-03-04T17:38:18Z

anything blocking this PR from being merged?

rasendubi marked this pull request as draft February 5, 2025 17:43

rasendubi changed the title ~~feat(dart): Dart SDK~~ FF-3753 feat(dart): Dart SDK Feb 5, 2025

rasendubi added 3 commits February 13, 2025 01:31

feat(dart): PoC implementation of SDK

a1132c7

feat(dart): boolean assignment, bandits, logging

21526f7

rasendubi mentioned this pull request Feb 17, 2025

Elixir SDK #208

Merged

4 tasks

rasendubi added 2 commits February 17, 2025 22:02

feat(dart): rest of assignment methods

7720878

test(dart): sdk-test-data tests

ca4cb55

rasendubi marked this pull request as ready for review February 17, 2025 21:11

rasendubi requested review from leoromanovsky, felipecsl, aarsilv and schmit February 17, 2025 21:11

rasendubi requested a review from typotter February 17, 2025 21:12

schmit reviewed Feb 19, 2025

View reviewed changes

rasendubi added 4 commits February 19, 2025 19:44

feat(dart): enable wasm_js for getrandom on wasm platform

ff76f07

feat(core,dart): abstract over async runtimes to support Dart web

e98d8b2

chore(dart): upgrade flutter_rust_bridge

dc47502

chore(dart): integrate with changeset

91a5dec

rasendubi force-pushed the feat-dart branch from 6c9f3b9 to 91a5dec Compare February 21, 2025 19:06

Merge remote-tracking branch 'origin/main' into HEAD

0fd3594

leoromanovsky reviewed Feb 22, 2025

View reviewed changes

fix: add .gitkeep for dart-sdk/lib/src/rust directory

a4ec8ca

rasendubi and others added 14 commits February 28, 2025 11:01

chore(dart): lower meta boundary

dc81fb3

fix(core): fix configuration poller running in wasm target

6de1192

fix(dart): properly default base url

a6c18e0

chore(dart): rename eppo_dart to eppo_sdk

e48ca58

This is used as the name of js/wasm generated files.

fix(dart): enable logging in web

f6ff55b

chore(dart): upload dart web files in ci

ac16171

chore(dart): CI to publish dart sdk

8ba7de2

docs(dart): add dart tag format to documentation

b068aa6

chore(dart): add license file

ff855ef

chore(dart): add missing id-token permissions for write

9b27a09

chore(dart): refresh pub.dev auth token?

10cc9cd

chore(dart): release on tag, not release event 🤷

94f9b7f

chore(dart): silence publish dry-run error code

ac05856

felipecsl reviewed Feb 28, 2025

View reviewed changes

leoromanovsky reviewed Feb 28, 2025

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felipecsl approved these changes Feb 28, 2025

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rasendubi added 2 commits March 3, 2025 16:49

chore: add changeset for openssl->rustls change

f5dc034

chore(dart): build release artifacts for web

69fdcb2

This reduces wasm file from 12M down to 2M.

This was referenced Mar 3, 2025

Suggested fix for libatomic bug on i686 ? PyO3/maturin-action#331

Closed

chore(ci): dart-sdk rust cross compile for Android target #222

Merged

leoromanovsky merged commit a4da91f into main Mar 4, 2025
39 checks passed

leoromanovsky deleted the feat-dart branch March 4, 2025 18:01

github-actions bot mentioned this pull request Mar 4, 2025

chore: bump versions before release #226

Merged


		Make async runtime abstract.

		This introduces an `AsyncRuntime` trait that allows us to abstract over different async runtimes. This is required to support Dart SDK that doesn't use tokio runtime in web build.

		/// `AsyncRuntime` abstracts over various Rust's async runtimes with minimal interface. This is
		/// usually just a tokio Handle but Dart SDK in wasm uses a custom implementation.

FF-3753 feat(dart): Dart SDK #197

FF-3753 feat(dart): Dart SDK #197

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