@swc/wasm delaying process shutdown

[cspotcode]

Describe the bug

@swc/wasm appears to delay the graceful shutdown of a node process once it's loaded.

Input code

node -e 'require("@swc/wasm"); console.log("done.  Should ideally terminate immediately but is somehow delayed by @swc/wasm")'

The node process remains running for about 5 seconds after the log statement. I'm not sure if @swc/wasm is setting some sort of timer or why the process is staying up.

Expected behavior

node process gracefully terminates immediately after the log statement.

Version
The version of @swc/wasm: 1.2.45
OS: Ubuntu Linux
node: v14.15.3

[Brooooooklyn]

I think this may be a wasm problem, wasm needs to be read, loaded and parsed asynchronously, and perhaps this process cannot be interrupted

[cspotcode]

I don't think that is the issue, because I can invoke transformSync to prove that the WASM is executable much earlier. Also, if it were an issue with async compilation, that would mean that WASM takes a full 5 seconds to load, which I think we can agree seems very wrong.

Here is the updated reproduction. It uses transformSync, then logs the date. Then the process waits 5 seconds before terminating, at which point a subsequent process logs the date again. This shows the magnitude of the delay.

node -e 'console.log(require("@swc/wasm").transformSync("const foo = 123", {})); console.log(new Date)' ; node -e 'console.log(new Date)'

Sample output:

2021-01-23T21:41:57.192Z
2021-01-23T21:42:01.869Z

[yisibl]

It looks like it's been greatly improved in Node.js 18.3.0, so you can try it out.
nodejs/node#36616 (comment)