feat: add --expose-gc flag

[anurag-roy]

Addresses #3

[mcollina]

Can you add it to the docs?

[anurag-roy]

I was trying out a few different ways to achieve this.

Since we are using run from node:test here and not spawning a new process, we have two options:

1. Enable gc dynamically (without passing flags to node)

import { setFlagsFromString } from 'node:v8';
import { runInNewContext } from 'node:vm';

if (args.values['expose-gc'] && typeof global.gc !== 'function') {
 setFlagsFromString('--expose-gc');
 global.gc = runInNewContext('gc');
}

I tried this, but was unable to use gc inside my tests

2. Spawn a node child process where we pass the --expose-gc flag

if (args.values['expose-gc'] && typeof global.gc !== 'function') {
 try {
   await execa('node', ['--expose-gc', ...process.argv.slice(1)], {
     stdio: 'inherit',
     env: {
       ...process.env
     }
   })
   process.exit(0)
 } catch (error) {
   process.exit(1)
 }
}

This one does work, but I'm not sure if this is the best way. Any pointers? @mcollina

[mcollina]

I think you can set it to process.env.NODE_OPTIONS before calling run

[anurag-roy]

No that will not work, since it isn't a node option it's a v8 flag.

$ node --v8-options

--expose-gc (expose gc extension)
        type: bool  default: false

And passing it as NODE_OPTIONS gives this error

node: --expose-gc is not allowed in NODE_OPTIONS

[mcollina]

I recommend you to open an issue on nodejs to add the possibility to pass nodeOptions to run.

Until that happens, using execa is ok.

[mcollina]

lgtm

[mcollina]

I've made a mistake and landed this while tests are failing on Node v21. Could you send a follow-up pr to fix?

[anurag-roy]

Yes sure, let me check why they are failing on v21

[anurag-roy]

Hey @mcollina you might want to take a look at this, something very weird is happening.

All tests are failing on v21.5, but passing on v21.4. When we are running node borp.js through execa, it seems as if none of the tests inside that child process are running. This is the output from execa

TAP version 13
1..0
# tests 0
# suites 0
# pass 0
# fail 0
# cancelled 0
# skipped 0
----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------|---------|----------|---------|---------|-------------------
All files |       0 |        0 |       0 |       0 |
----------|---------|----------|---------|---------|-------------------
# todo 0
# duration_ms 8.481937

Do you have any idea what might be the issue?

[mcollina]

Here is the fix: #5

[anurag-roy]

Awesome! All tests passing now!