feat: add npm set-script

[Yash-Singh1]

Summary

This PR introduces the set-script command. It accepts two arguments, the script name and the command as said in RFC 0016

References

Adds in RFC 0016: https://github.com/npm/rfcs/blob/latest/accepted/0016-set-script-command.md

[ljharb]

What happens if a package uses npm set-strict in a postinstall script? Should perhaps this command explicitly fail in that scenario? (I realize that a package can probably already do this, but this command might make it easier)

[Yash-Singh1]

What happens if a package uses npm set-strict in a postinstall script? Should perhaps this command explicitly fail in that scenario? (I realize that a package can probably already do this, but this command might make it easier)

Any suggestions on how to detect or identify if it is being called from postinstall?

[ruyadorno]

What happens if a package uses npm set-strict in a postinstall script? Should perhaps this command explicitly fail in that scenario? (I realize that a package can probably already do this, but this command might make it easier)

Right, I've read through the original RFC discussion to find that there was no definitive stance on it so it didn't make it to the RFC itself - I'm ok with that extra check being there since it's unlikely to be an issue to 99% of users.

Any suggestions on how to detect or identify if it is being called from postinstall?

You can check for process.env.npm_lifecycle_event === 'postinstall' and throw an error then 😊

[ruyadorno]

Thank you so much @Yash-Singh1 for picking this up from the RFCs and turning it into actual code 😄 This is looking very good, I think it just needs to adjust some details I left in the review + addressing lifecycle check from @ljharb 😊

For tests and docs you can refer to other commands for examples but definitively let us know if you need help/guidance. Thanks again! 🎉

[ljharb]

This doesn't seem like it has actual tests?

[ljharb]

seems good to me, but i don't see any unit tests.

[Yash-Singh1]

@ljharb @ruyadorno I am ready to merge from my end.

[ruyadorno]

Some very minor suggestions to polish things up even more but otherwise we're looking good to ship it!