Forked cluster does not fix up process.execArgv after filename when executed by module.runMain()

[JLHwung]

• Version: v15.5.1
• Platform: Darwin jh.local 20.2.0 Darwin Kernel Version 20.2.0: Wed Dec 2 20:39:59 PST 2020; root:xnu-7195.60.75~1/RELEASE_X86_64 x86_64
• Subsystem: cluster, module

What steps will reproduce the bug?

node --expose_gc ./wrapper.js ./payload.js

See https://gist.github.com/JLHwung/631dfbf4a4c68d85ae7a9b7ab5fa9754 for ./wrapper.js and ./payload.js.

How often does it reproduce? Is there a required condition?

What is the expected behavior?

It should print

[Function: gc] true
[Function: gc]

What do you see instead?

[Function: gc] true
undefined

Additional information

Context: babel/babel#12635

process.execArgv is

["/path/to/babel-node.js", "--expose_gc"]

It seems that forked clusters stop fixing up execArgv after "/path/to/babel-node.js" is read. If I place "/path/to/babel-node.js" after "--expose_gc", it works as expected.

As module.runMain is undocumented. The actual behaviour may be limbo. However as it is used by both Babel and npx, would you consider document it or deprecate it via better approach? 😄

[JLHwung]

Closing this as the executed filename should come after Nodejs specific command-line options.