Deno hangs after succesfully executing npm-package library call

[aukeroorda]

> deno --version
deno 1.41.3 (release, x86_64-apple-darwin)
v8 12.3.219.9
typescript 5.3.3

MRE

Can be found at: https://github.com/aukeroorda/mre-deno-hang/tree/main

1. Verify the contents of the repo
2. Install the paper-js library as specified in the package file:

   npm install

3. Run deno:

   deno run mre.ts

4. Allow reading of node_modules: y
5. Observe that code executes to the end of the mre.ts script, but Deno hangs.

Note:
Deno doesn't hang anymore if the following lines 20 and 21 are commented out: https://github.com/aukeroorda/mre-deno-hang/blob/6c3d8d0f313141bff39ffc0906780189668b055d/mre.ts#L20-L21

Inspecting using chromium

I've tried to inspect what is going on with this library call using the chromium debugger, but I can't really see much, as the call gets 'hijacked' by a call to node:timers setInterval() function, and I lose the trace of the library function call here.

[lucacasonato]

I presume this is related to NAPI, as paper uses node-canvas. I have not tested that though - so it's just a theory :)

[devsnek]

According to tokio-console this is getting stuck waiting for a timer but more investigation is needed to figure out exactly what timer.

[kt3k]

Deno fails to simulate Node.js in paper.js because it uses self global variable to detect Node.js https://github.com/paperjs/paper.js/blob/92775f5279c05fb7f0a743e9e7fa02cd40ec1e70/src/init.js#L32

(In Deno, paper.agent becomes { platform: undefined }, in Node.js it is:

{
  platform: 'mac',
  mac: true,
  version: '20.15.0',
  versionNumber: 20.15,
  name: 'node',
  node: true
}

If the platform is not Node.js, view._autoUpdate becomes true:

https://github.com/paperjs/paper.js/blob/92775f5279c05fb7f0a743e9e7fa02cd40ec1e70/src/view/View.js#L120

If view._autoUpdate is true, it calls view.requestUpdate method:

https://github.com/paperjs/paper.js/blob/92775f5279c05fb7f0a743e9e7fa02cd40ec1e70/src/item/Project.js#L97

Which calls polyfilled version of requestAnimationFrame in Deno:

https://github.com/paperjs/paper.js/blob/92775f5279c05fb7f0a743e9e7fa02cd40ec1e70/src/view/View.js#L225

Which internally calls setInterval, which is never cleared.

https://github.com/paperjs/paper.js/blob/92775f5279c05fb7f0a743e9e7fa02cd40ec1e70/src/dom/DomEvent.js#L120

One of workarounds is deleting globalThis.self before importing paper:

delete globalThis.self;
const paper_import = await import("paper");
const paper = paper_import.default;
globalThis.paper = paper;
paper.setup();
const pathdata = "M 0 0 C 0 10 10 10 10 0 z"; 
const path = new paper.Path(pathdata);
console.log({ path }); 
console.log(paper.agent);

The above script exits immediately and prints paper.agent with node field set to true.

[kt3k]

One solution might be hiding globalThis.self while evaluating npm packages. WDYT?

[bartlomieju]

Seems like a reasonable solution, self is not defined in Node.js

[aukeroorda]

Hi -
Just running this again, but on my end it still hangs after execution, using the same MRE as stated earlier. This is using the updated deno version:

> deno --version
deno 1.43.5 (release, x86_64-apple-darwin)
v8 12.4.254.13
typescript 5.4.5

so I'm not sure if the PR to fix this issue actually fixes it.

Using delete globalThis.self; before the import does fix it in the MRE though!

[marvinhagemeister]

@aukeroorda Deno v1.43.5 is a bit older. The latest version at the time of this writing is v1.45.5

[aukeroorda]

Thanks for informing me! I thought I updated recently, but apparently not that recently! It is indeed solved.
Thanks