Separator added for `joinToNode` if first value is `undefined`

[chriszwickerergon]

Langium version: 4.1.0
Package name: CLI / Generator

Steps To Reproduce

1. Try console.log(toString(expandToNode`ex: ${joinToNode(["foo", undefined], {separator: ","})}`))

The current behavior

Output is ex: foo, instead of ex: foo

The expected behavior

It should be ex: foo - as it is for console.log(toString(expandToNode`ex: ${joinToNode([undefined, "foo"], {separator: ","})}`))

[sailingKieler]

Well-spotted @chriszwickerergon!
We didn't pay too much attention to the cases of undefined list or stream items, yet, thank you for your report.

PR #2090 should fix that. Would you try and test?

[chriszwickerergon]

Thank you for the fix!

I've monkey patched the code, removed my workaround and my tests still run. Looking forward to this being merged and shipped!