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This allows to spawn background tasks, and will allow to use the idle time when the device is showing some UX flow to perform work.
For the moment, app.rs remains synchronous, therefore this is only a breaking change for apps using lower-level ux functionality (the 'vnd-test' and, to a small extent, the 'vnd-sadik') app. Making app.rs also work asynchronously will be done in the following commits.
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Pull request overview
This PR introduces a cooperative async/futures execution model to the Vanadium app SDK and migrates the SDK UX + multiple V-Apps to use async handlers by default, enabling background “worker tasks” that run while users are in UX flows.
Changes:
- Added a single-threaded cooperative executor (
block_on,spawn,yield_now) toapp-sdk. - Switched the App framework handler signature and UX APIs to async, and migrated existing apps/handlers accordingly.
- Added a
#[sdk::handler]attribute macro to ergonomically adaptasync fnhandlers to theAppBuilderhandler type; added a newapps/asyncexample app + client.
Reviewed changes
Copilot reviewed 33 out of 33 changed files in this pull request and generated 12 comments.
Show a summary per file
| File | Description |
|---|---|
| macros/src/lib.rs | Registers the new handler proc-macro alongside existing derives. |
| macros/src/handler.rs | Implements the #[handler] attribute macro transforming async fn into a boxed-future handler. |
| macros/Cargo.toml | Enables syn’s full feature for parsing function items. |
| apps/test/app/src/handlers/show_ux_screen.rs | Updates UX calls to async by wrapping with executor::block_on in a sync test harness. |
| apps/template/generate/app/src/main.rs | Migrates template-generated V-App to async UI flow and async handler via #[sdk::handler]. |
| apps/template/generate/app/Cargo.toml.liquid | Points generated apps at a git dependency configuration for the async SDK branch. |
| apps/template/app/src/main.rs | Migrates the in-repo template app to async UI flow and async handler via #[sdk::handler]. |
| apps/template/app/Cargo.toml | Points the template at a git dependency configuration for the async SDK branch. |
| apps/sadik/app/src/main.rs | Converts process_message to async handler and adapts event loop usage. |
| apps/rps/app/src/main.rs | Converts app UX and message handling to async + updates tests to block_on. |
| apps/bitcoin/app/src/main.rs | Converts the main request dispatcher and handler to async. |
| apps/bitcoin/app/src/handlers/sign_psbt.rs | Migrates signing UX/warnings to async and updates tests to block_on. |
| apps/bitcoin/app/src/handlers/register_account.rs | Migrates registration UX flow to async and updates tests to block_on. |
| apps/bitcoin/app/src/handlers/get_extended_pubkey.rs | Migrates xpub display UX flow to async and updates tests to block_on. |
| apps/bitcoin/app/src/handlers/get_address.rs | Migrates address display UX flow to async and updates tests to block_on. |
| apps/async/vapp.code-workspace | Adds a workspace file for the new async example app/client. |
| apps/async/client/src/main.rs | Adds a Tokio-based CLI to drive the async demo V-App. |
| apps/async/client/src/lib.rs | Creates a dual-mode (std client / no_std shared types) crate layout. |
| apps/async/client/src/common.rs | Defines shared Command enum for app/client messaging. |
| apps/async/client/src/client.rs | Implements a transport-backed client API for the demo app. |
| apps/async/client/Cargo.toml | Adds the new client crate with feature flags and optional deps. |
| apps/async/client/.cargo/config.toml | Forces single-threaded tests for the client crate. |
| apps/async/app/src/main.rs | Adds a new demo V-App showcasing sync vs async work with background tasks. |
| apps/async/app/justfile | Adds build/run recipes for the demo app. |
| apps/async/app/Cargo.toml | Adds the demo app crate configuration and vapp metadata. |
| apps/async/app/.vscode/settings.json | Adds rust-analyzer settings for the demo app. |
| apps/async/app/.cargo/config.toml | Adds RISC-V target flags + single-threaded tests for the demo app. |
| apps/async/README.md | Documents building/running the async demo app + client. |
| app-sdk/src/ux.rs | Converts UX primitives (events, waits, review flows, confirm flows, info) to async. |
| app-sdk/src/lib.rs | Exposes the executor module and re-exports #[handler] + task-related types. |
| app-sdk/src/executor.rs | Introduces a cooperative single-threaded async executor with tests. |
| app-sdk/src/app.rs | Updates handler type to async, integrates executor driving, adds background task APIs (spawn_task, TaskHandle). |
| app-sdk/Cargo.toml | Adds dependency on vanadium_macros for #[sdk::handler] re-export. |
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A new procedural #[handler] macro added to the SDK allows to hide almost all the additional complexity migrating from the old to the new approach, which mostly amounts to adding 'async' wherever appropriate.
It is wasteful to continue processing a task that is dropped. This allows aborting the computation on the first occasion, if the task is no longer useful.
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Pull request overview
Copilot reviewed 38 out of 38 changed files in this pull request and generated 3 comments.
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- Validate arguments and return value - Make sure there are no attribute arguments - Preserve where-clause (if present), instead of dropping silently
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This adds an
executorfor futures/async functions in the app-sdk, and migrates the UX framework and the existing V-Apps to use anasyncapproach by default.The big win of this approach is that it becomes rather easy to create 'worker tasks' that perform useful computations while the device is idle. Thanks to the Rust's futures, the executor, and some syntactic sugar, this comes at very little added complexity when writing V-Apps.
Some use cases that might be useful in order to improve tha V-Apps UX and (perceived) performance: