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lib: expose setupInstance method on WASI class #57214

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lib: expose setupInstance method on WASI class #57214

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7aeb0af
lib: expose `setupInstance` method on WASI class
toyobayashi Feb 25, 2025
c489dec
lib: fix lint
toyobayashi Feb 25, 2025
c88140f
lib: fix lint
toyobayashi Feb 25, 2025
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37 changes: 24 additions & 13 deletions lib/wasi.js
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Original file line number Diff line number Diff line change
Expand Up @@ -7,11 +7,16 @@ const {
ObjectEntries,
String,
Symbol,
globalThis,
} = primordials;
const {
WebAssembly,
} = globalThis;

const {
ERR_INVALID_ARG_VALUE,
ERR_WASI_ALREADY_STARTED,
ERR_INVALID_ARG_TYPE,
} = require('internal/errors').codes;
const {
emitExperimentalWarning,
Expand All @@ -34,15 +39,6 @@ const kBindingName = Symbol('kBindingName');

emitExperimentalWarning('WASI');


function setupInstance(self, instance) {
validateObject(instance, 'instance');
validateObject(instance.exports, 'instance.exports');

self[kInstance] = instance;
self[kSetMemory](instance.exports.memory);
}

class WASI {
constructor(options = kEmptyObject) {
validateObject(options, 'options');
Expand Down Expand Up @@ -118,14 +114,30 @@ class WASI {
this[kInstance] = undefined;
}

setupInstance(instance, memory) {
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This works great, I'd just make two suggestions - changing the name to setupBindings() or finalizeBindings() and having a { memory } object for extensibility as the second argument.

  1. Formally speaking, we are not setting up the instance here, rather we are setting up the WASI host bindings themselves, closing the loop on the deferred instance bindings being passed back to WASI. Therefore I think setupBindings(), finalizeBindings() or finalizeWASI() or something like that might make more sense as a name than setupInstance().
  2. Right now we just want to bind memory, but in theory there might be benefit in future binding other things like tables or function registrations from the instance. To give some flexibility it would help to have setupBindings(instance, { memory = instance.exports.memory } = {}) as the signature.

Otherwise the overall approach seems great to me though.

validateObject(instance, 'instance');
validateObject(instance.exports, 'instance.exports');
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We should also move the if (this[kStarted]) throw new ERR_WASI_ALREADY_STARTED() error here as we should't allow this to be called twice.


if (memory != null) {
if (!(memory instanceof WebAssembly.Memory)) {
throw new ERR_INVALID_ARG_TYPE('memory', 'WebAssembly.Memory', memory);
}
this[kSetMemory](memory);
} else {
this[kSetMemory](instance.exports.memory);
}

this[kInstance] = instance;
this[kStarted] = true;
}

// Must not export _initialize, must export _start
start(instance) {
if (this[kStarted]) {
throw new ERR_WASI_ALREADY_STARTED();
}
this[kStarted] = true;

setupInstance(this, instance);
this.setupInstance(instance);

const { _start, _initialize } = this[kInstance].exports;

Expand All @@ -148,9 +160,8 @@ class WASI {
if (this[kStarted]) {
throw new ERR_WASI_ALREADY_STARTED();
}
this[kStarted] = true;

setupInstance(this, instance);
this.setupInstance(instance);

const { _start, _initialize } = this[kInstance].exports;

Expand Down
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