embedder_main bootstrap scripts are missing some globals

[SnirBroshi]

When using LoadEnvironment with a string parameter, e.g.

https://github.com/nodejs/node/blob/2a4452a53af65a13db4efae474162a7dcfd38dd5/test/embedding/embedtest.cc#L76-L82

the script gets access to require and process, but doesn't have access to other variables accessible to bootstrap code in lib/internal/, such as primordials and internalBinding.

This is the code responsible:

https://github.com/nodejs/node/blob/2a4452a53af65a13db4efae474162a7dcfd38dd5/src/node_builtins.cc#L368-L373
https://github.com/nodejs/node/blob/2a4452a53af65a13db4efae474162a7dcfd38dd5/src/node_builtins.cc#L429-L434

This is a problem when copying code from node's bootstrappers, since the code relies on such globals.
It seems intentional that embedder_main scripts are not provided these, but is there a reason? @joyeecheung

Other than primordials and internalBinding there is also module and exports which builtin modules get access to.
It seems that returning a value from the script passed to LoadEnvironment returns it to the caller, so I'm not sure if having module.exports will do anything.

So should I open a PR to give access to primordials and internalBinding? And what about module and exports?

[SnirBroshi]

Update: #46825 now we also lost access to require internals :(

[joyeecheung]

I think the reason was that we do not want to be burdened of maintaining any compatibility of the internals for embedders. It might be okay to add an option to expose them, but not by default and this should be guarded with explicit warning that frequent breakages should be expected.