Test wasm32 without js by youknowone · Pull Request #6283 · RustPython/RustPython

youknowone

Walkthrough

The PR replaces the broken wasm test infrastructure by relocating the wasm crate from wasm/wasm-unknown-test/ to a new structured example project at example_projects/wasm32_without_js/. It introduces a wasm producer crate (rustpython-without-js) and a wasm runtime consumer (wasm-runtime) using Wasmer, along with CI workflow updates.

Changes

Cohort / File(s)	Summary
CI Workflow Update `.github/workflows/ci.yaml`	Updated wasm test step to reference new project structure; changed working directory from `wasm/wasm-unknown-test` to `example_projects/wasm32_without_js`, adjusted cargo build manifest paths, and added execution step for the wasm runtime.
Old WASM Test Crate Removal `wasm/wasm-unknown-test/Cargo.toml`, `wasm/wasm-unknown-test/src/lib.rs`	Deleted the broken wasm test crate entirely, removing manifest and FFI entry points (`eval` and `__getrandom_v03_custom`).
Example Project Documentation & Config `example_projects/wasm32_without_js/.gitignore`, `example_projects/wasm32_without_js/README.md`	Added project-level gitignore patterns and comprehensive build/run documentation for the wasm32 example.
WASM Producer Crate `example_projects/wasm32_without_js/rustpython-without-js/Cargo.toml`, `example_projects/wasm32_without_js/rustpython-without-js/src/lib.rs`	Created new cdylib crate with FFI bridge exposing `eval()` C function; implements Python interpreter execution via rustpython-vm and declares getrandom hook; also declares external C function stubs (`kv_get`, `kv_put`, `get_code`, `print`).
WASM Runtime Crate `example_projects/wasm32_without_js/wasm-runtime/.gitignore`, `example_projects/wasm32_without_js/wasm-runtime/Cargo.toml`, `example_projects/wasm32_without_js/wasm-runtime/README.md`, `example_projects/wasm32_without_js/wasm-runtime/src/main.rs`	Created new Wasmer-based runtime crate with in-memory KV store backend; implements host-side FFI functions (`kv_get`, `kv_put`, `print`), loads and instantiates wasm module, manages memory references, and executes eval function.

Sequence Diagram

sequenceDiagram
    participant Host as Host Runtime<br>(main.rs)
    participant WasmModule as WASM Module<br>(eval)
    participant RustPython as RustPython VM
    participant KVStore as KV Store

    Host->>Host: Load WASM module from path
    Host->>Host: Initialize KV store with code
    Host->>WasmModule: Call eval(code_ptr, code_len)
    activate WasmModule
    WasmModule->>RustPython: Create Interpreter
    RustPython->>RustPython: Execute Python expr "1 + 3"
    RustPython-->>WasmModule: Result repr
    WasmModule->>Host: Call print(msg_ptr, msg_len)
    activate Host
    Host->>Host: Read string from WASM memory
    Host->>Host: Print to stdout
    Host-->>WasmModule: return 0
    deactivate Host
    WasmModule-->>Host: return 0 (success)
    deactivate WasmModule
    Host->>Host: Report result

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

WASM memory safety & pointer handling: Both producer and consumer use unsafe extern FFI with raw pointer dereference; verify boundary conditions and memory access correctness
Getrandom integration: Custom __getrandom_v03_custom hook implementation needs validation; ensure it doesn't break wasm runtime
FFI signature matching: Verify that function signatures and calling conventions align between rustpython-without-js/src/lib.rs and wasm-runtime/src/main.rs
Wasmer integration: Review memory environment setup and function environment exports in the runtime
CI workflow paths: Confirm all manifest and artifact paths resolve correctly in the new structure

Possibly related PRs

Fix wasm32-unknown-unknown target build #6278: Modifies the same wasm FFI entrypoint in wasm/wasm-unknown-test/src/lib.rs, adjusting attributes and wasm-related dependencies.
Move wasm/lib -> crates/wasm #6280: Updates CI workflow references to the project's wasm crate layout, modifying manifest and test paths for wasm-related steps.
wasm_js rustlfags on top workspace #6116: Configures getrandom's WebAssembly backend via rustflags; this PR adds a complementary custom getrandom hook (__getrandom_v03_custom).

Poem

🐰 Hop, hop, a test reborn! 🌟
From broken paths, a new structure sworn,
Producer and runtime dance in tandem grace,
Wasm flows through memory's bounded space,
No more broken dreams—the bridge is strong! 🎉

Pre-merge checks and finishing touches

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Test wasm32 without js' directly and specifically refers to the main change: adding a working test and example for wasm32 compilation without JavaScript support.
Linked Issues check	✅ Passed	The PR successfully addresses issue #6281 by replacing the broken wasm-unknown-test with a functioning example and test setup that compiles and executes correctly.
Out of Scope Changes check	✅ Passed	All changes are scoped to replacing the broken wasm32 test setup with a new working example and runtime, directly addressing the issue without introducing unrelated modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

📝 Generate docstrings

🧪 Generate unit tests (beta)

Create PR with unit tests
Post copyable unit tests in a comment

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