Hacktoberfest 2026: le issue che i maintainer hanno segnato per ottobre, aperte e adatte ai principianti. Sfoglia le issue Hacktoberfest

Composing labelled (`implements`) imports of one interface gives output wit-parser panics on

Aperta
  • Qualcosa non va?
#219 0 commenti 0 reazioni 0 assegnatari Vedi su GitHub

Nessuno ha ancora preso questa issue.

Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
45/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
rust, wasm
Ambito
tooling

Direzione di ricerca

The panic is in the wit-parser dependency (decoding.rs:797 asserts prev.is_none()), but the fix belongs in wac-graph's CompositionGraph::encode, which currently gives every labelled (implements "I") import one shared instance type. Build the issue's reproduction (a consumer importing the same interface that defines a type under primary and backup), then trace where encode interns and emits instance types, covering both the implicit-import path and explicit CompositionGraph::import nodes. Done is the repro's final wit_parser::decoding::decode(&composed) succeeding, with one instance type per labelled import as wit-component encodes it.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

When a composition has several (implements "I") imports of the same interface, CompositionGraph::encode gives them all one instance type:

(import "primary" (implements "test:test/logger") (instance (;0;) (type 0)))
(import "backup"  (implements "test:test/logger") (instance (;1;) (type 0)))

Several labels for one interface is the case labelled imports exist for (#200). This happens:

  • through implicit imports (an instantiated component's labelled imports left unsatisfied);
  • through explicit CompositionGraph::import nodes.

The output validates, and wasmtime runs it. But when the interface defines a type, wit-parser's decoder panics on it, and so does every tool built on that decoder:

  • wasm-tools component wit;
  • wit-bindgen;
  • jco. jco transpile aborts the same way (it uses wit-parser 0.259), so the composition can't be run in JavaScript.

The input component decodes fine: it's wit-component's shape, with one instance type per labelled import. Only wac's output has the shared type.

Reproduction

Cargo.toml:

[package]
name = "wac-implements-repro"
version = "0.1.0"
edition = "2024"

[dependencies]
wac-graph = "=0.12.0"
wit-parser = "=0.258.0"
wat = "1"

src/main.rs:

use wac_graph::{types::Package, CompositionGraph, EncodeOptions};

/// A component importing one interface, which defines a type, under two
/// labels: the shape wit-component produces (one instance type per import).
const CONSUMER: &str = r#"
(component
  (type (instance
    (type (enum "debug" "info"))
    (export "level" (type (eq 0)))
    (type (func (param "level" 1) (param "message" string)))
    (export "log" (func (type 2)))))
  (import "primary" (implements "test:test/logger") (instance (type 0)))
  (type (instance
    (type (enum "debug" "info"))
    (export "level" (type (eq 0)))
    (type (func (param "level" 1) (param "message" string)))
    (export "log" (func (type 2)))))
  (import "backup" (implements "test:test/logger") (instance (type 1)))
)
"#;

fn main() {
    let consumer = wat::parse_str(CONSUMER).unwrap();
    // The input decodes fine.
    wit_parser::decoding::decode(&consumer).expect("the consumer decodes");
    println!("consumer: decodes");

    let mut graph = CompositionGraph::new();
    let package = Package::from_bytes("test:consumer", None, consumer, graph.types_mut()).unwrap();
    let package = graph.register_package(package).unwrap();
    graph.instantiate(package);
    let composed = graph.encode(EncodeOptions::default()).unwrap();
    println!("composed: {} bytes, validated by wac", composed.len());

    // The composition does not: wit-parser panics.
    wit_parser::decoding::decode(&composed).expect("the composition decodes");
    println!("composition: decodes");
}

Output:

consumer: decodes
composed: 348 bytes, validated by wac

thread 'main' panicked at wit-parser-0.258.0/src/decoding.rs:797:29:
assertion failed: prev.is_none()

Expected

The composition decodes as the input does: each labelled import has its own instance type, as wit-component encodes it.

Related

  • bytecodealliance/wasm-tools#2506
Lingua principale
Rust
Stelle
206
Fork
42
Merge medio
4g 9m
PR unite (30g)
4

Preparare l'ambiente

Questo progetto non fornisce container di sviluppo, Dockerfile né guida per i contributori, quindi l'ambiente è a tuo carico: parti dal suo README e consulta la nostra guida al primo contributo per i passaggi generali.

Come iniziare

  1. Leggi tutta la issue e poi la guida ai contributi del progetto.
  2. Commenta sulla issue per dire che te ne occupi tu — evita che due persone facciano lo stesso lavoro.
  3. Fai un fork del repository e lavora su un branch.
  4. Apri una pull request che faccia riferimento al numero della issue.

Altre issue di bytecodealliance/wac

Tutte le issue di bytecodealliance/wac

Issue simili

Altre issue su Rust

Ricevi le nuove issue nella tua casella

Un breve riepilogo di issue GitHub adatte ai principianti.