Memory leaks HTML Modules

[NekR]

Forgot it isn't about only one spec. This is an issue about HTML Modules.

It looks like there will be a memory leak because of exporting nodes from one document to another, meaning that the imported document always will be in memory, even if you removed its contents from the current document's tree. It will have to be somehow unloaded.

Is the intended usage of it only with dynamic (import(...)) imports? Because I don't know anyway to de-reference static ES Modules.

[Jamesernator]

As it stands all modules memory leak because no modules (HTML or ESM or otherwise) can be collected until a page is closed.

Why? Because every module must only be evaluated exactly once, hence because we can dynamically import a module it could at any point be re-imported. However because we're only allowed to evaluate a module once it must be stored indefinitely as long as the page lives.

For example say we have the module:

// bar.mjs

// This will only be printed once, ever, the module can never be collected
// once evaluated because it might still be re-imported
// sometime in the future
console.log(3)

export const x = 12

// some-file.mjs
import randomIdentifier from '...somewhere...'

async function main() {
  await import('./bar.mjs')
  while (true) {
    // Because this could re-import bar.mjs at any point we can never
    // collect the module created from bar.mjs, so it stays indefinitely
    const module = await import('./' + randomIdentifier(3) + '.mjs')
    console.log(module.x)
    await new Promise(resolve => setTimeout(resolve, 1000))
  }
}

main()

then no garbage collection will ever happen to bar.mjs (or some-file.mjs for that matter either).

Because HTML modules are simply another type of module they will consequently leak memory. However as long as you're not importing an arbitrarily growing collection of modules this shouldn't be a problem.

[domenic]

Modules can be collected. Their exports cannot be.

[travisleithead]

Unless anyone has any new information here, I think that there's not much more progress we can make on this issue. (And if there is new information to surface, let's please open the issue against the HTML spec.)