why is it a fatal operation?

i believe it's due to nodejs/node#40696 adding them to the official API

According to the documentation the read-only property called "closed" was added to the Writable class in v18.0.0 of nodejs. And it also looks like the property "_closed" is used internally in the SMTPConnection class. So this patch looks ok.

Thanks for the patch. May I ask, when will the new version be published ?

The test suite coverage is very low, so removing .closed property does not break the tests. This does not mean you can just remove it. At the least, you should try to find where this property is actually used and make sure that the existing functionality is not broken with the PR.

@andris9 it is now a conditional set, achieved by consulting a new getter-only prop on SMTPStream that determines if the closed property is itself a getter-only prop. it does this by using the time-honored technique of returning false if prop assignment throws.

...of course, since it's a (likely tiny) perf hit, i'll stew on it for years until v16 goes EOL & i can re-submit the original changeset 😆

thanks!