EdisonJwa
2bbad5feb9
Proof-of-concept proving the Flutter/Rust bridge exit criterion from docs/architecture/proof-of-concept-plan.md §2: "Flutter can call Rust and receive event stream data." The spike exposes one synchronous fallible command (greet) returning a typed GreetResult / GreetError DTO, and one async event stream (counter_stream) emitting typed CounterTick events. The Flutter app demonstrates both flows on a Material 3 surface; the headless test suite in test/poc_verification_test.dart exercises the same API directly through dart:ffi. Verified on 2026-05-13 (Linux desktop, Flutter 3.41.9 / Dart 3.11.5, flutter_rust_bridge 2.12.0, Rust 1.95). All three tests pass: - greet() returns typed result for valid input - greet() surfaces typed error for empty input - counterStream() delivers the expected event sequence Authority: PoC plan §2, DEC-014 (typed Flutter/Rust bridge), SAD-068, SDD-079, SysDes-049. Naming note: the PoC plan lists this as flutter-rust-bridge-hello, but Dart pubspec.yaml package names require underscores; the directory uses underscores accordingly. Not product code; not promoted into chanora_bridge. Layout note: includes the full Flutter platform scaffold (android, ios, macos, windows, web, linux). Only the Linux desktop target has been built and verified.
2.7 KiB
2.7 KiB
Verification record — flutter_rust_bridge_hello
Result
PASS. The PoC exit criterion (from
docs/architecture/proof-of-concept-plan.md §2: "Flutter can call Rust
and receive event stream data") is met.
Environment
| Field | Value |
|---|---|
| Date | 2026-05-13 |
| Host OS | Linux (Arch, kernel 7.0.5-arch1-1, x86_64) |
| Flutter | 3.41.9 stable (Dart 3.11.5) |
| Rust toolchain | stable 1.95.0 |
flutter_rust_bridge (Rust + Dart) |
2.12.0 |
flutter_rust_bridge_codegen |
2.12.0 |
| Target | linux desktop (x86_64-unknown-linux-gnu) |
Reproduction
# 1. Generate Dart bindings + Rust glue from rust/src/api.
flutter_rust_bridge_codegen generate
# 2. Build the Linux desktop bundle (this builds the cdylib too, via cargokit).
flutter build linux --debug
# 3. Run the headless verification test. The cdylib lives in the build bundle,
# so we point dart:ffi at it via LD_LIBRARY_PATH.
LD_LIBRARY_PATH="$PWD/build/linux/x64/debug/bundle/lib:$LD_LIBRARY_PATH" \
flutter test test/poc_verification_test.dart
Observed result
00:00 +0: loading /home/.../test/poc_verification_test.dart
00:00 +0: (setUpAll)
00:00 +0: Chanora FRB hello PoC greet() returns typed result for valid input
00:00 +1: Chanora FRB hello PoC greet() surfaces typed error for empty input
00:00 +2: Chanora FRB hello PoC counterStream() delivers the expected event sequence
00:00 +3: (tearDownAll)
00:00 +3: All tests passed!
What the verification proves
| Exit-criterion sub-claim | Evidence |
|---|---|
| Dart can call Rust | greet(name: 'Chanora') returns a GreetResult whose message field originated in Rust. |
| Typed result DTO crosses the boundary | GreetResult.elapsedMicros is a typed BigInt (Rust u64) deserialised correctly on the Dart side. |
| Typed error DTO crosses the boundary | greet(name: ' ') throws a GreetError instance on the Dart side (isA<GreetError>()); the Rust Err(...) arm is reached and reified as a Dart exception. |
| Dart can receive a Rust event stream | counterStream(count: 4, intervalMs: 50) yields exactly 4 ordered CounterTick events with seq = 0..3 and matching note payloads. |
| Streams close cleanly | The await for loop terminates on its own without timeout. |
Scope honestly NOT validated by this spike
- Performance characteristics of the bridge under load.
- Android, iOS, macOS, Windows targets.
- Lifecycle behaviour across Flutter hot-restart or Dart isolate boundaries.
- Cancellation semantics (Dart listener disconnect while Rust still produces).
- Behaviour with large/complex DTO graphs.
- Backpressure on the event stream.
- The full Chanora bridge DTO catalogue (owned by
chanora_bridge). - The "schema-controlled" half of DEC-014 — this PoC uses macro-driven generation only.