Setting `undefined` to `process.env.*` sets a `"undefined"` string value

[piranna]

Version

v20.4.0

Platform

Linux executive 6.2.0-25-generic #25-Ubuntu SMP PREEMPT_DYNAMIC Fri Jun 16 17:05:07 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

process.env

What steps will reproduce the bug?

Assign undefined to any value on process.env, for example process.env.foo = undefined.

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

Always.

What is the expected behavior? Why is that the expected behavior?

Since values assigned to entries in process.env are always casted to string and it's not possible to have any of them set to the undefined value, then it should be fully removed from the process.env object, allowing this way to get the entry unset.

What do you see instead?

I get the entry assigned the string undefined as value.

Additional information

The same happens with null, that gets assigned with the null string, so it's not possible to differenciate when setting it to null or the string "null". In this case I'm not sure of what should be the correct behaviour, since it's similar to what happens in SQL... Maybe setting the environment variable to an empty string?

For reference, assigning an object gets serialized as [object Object], that sort of makes sense,

[bnoordhuis]

Documented behavior and not subject to change; process.env is special and kind of magical.

Use delete process.env.whatever to unset properties.

[piranna]

I accept it being magical, and find the automatic casting to strings somewhat a smart trick, but setting undefined and being set to an undefined string, I find it more like a bug... For other values including null is fine for me, but for undefined, what are the reasons behind that behaviour?

[piranna]

Ok, current behaviour is properly documented at https://nodejs.org/api/process.html#processenv, but as deprecated. Can we left this issue open for when the current implicit conversion to string gets removed, so in addition of allowing only string, number, or boolean values (although I would be more strict and left just only strings), can be also accepted undefined as a way to remove the entry?

[bnoordhuis]

That "may result in a thrown error" is a bit of a paper tiger, it was already weakened from "will" to "may" (ref) and I don't expect it to ever happen, it would simply break too much of the ecosystem for no good reason.

can be also accepted undefined as a way to remove the entry?

That was proposed back in 2018 and was shot down for backwards compatibility reasons: #18158

The threshold for breaking changes is really, really high. And it should be.

[piranna]

@bnoordhuis, I've read the links you posted, it's sad the decision that was taken, specially by maintaining a broken API for backwards compatibility instead of fixing it :-( But I suppose I would need to deal with it... Luckily it doesn't have a direct impact on me, just found that on mid development and did a proper fix on my code, so this doesn't affect me, but anyway I thoung should notify it.