stream: eos use writableFinished when available

[ronag]

Use writableFinished when available. Improves compat with streamlike objects.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[lpinca]

The whole point of these new getters is to avoid using {_readable,_writable}State but in this case if the getter exists and returns false we use _writableState twice (first time in the getter itself and second time in the RHS of the "or" condition) so I'm not a fan of this change.

[ronag]

don't you think V8 is able to figure that out?

[lpinca]

Perhaps, I don't know.

[Trott]

Is there a desire to use writableFinished instead of _writableState in files such as this one, that are internal to streams, or should we only be doing that outside of the streams module itself (for example, in lib/http.js).

I thought the answer was "Only in files outside of the streams module itself."

The answer is relevant to determining how much work remains to be done to close what is literally the oldest open issue we have: #445.

[Trott]

Oh, wait, I see there's the "Improves compat with streamlike objects." comment, so the motivation isn't expanding usage of writableFinished for its own sake.

[lpinca]

Good point, I also missed that. It makes more sense now, approving.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/24585/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/24593/

thinking about this some more, probably could use a test?

[Trott]

Would it be not-too-onerous to add a test that would fail on master but pass with this change?

[Trott]

/ping @ronag Are you interested in adding a test to this?

[ronag]

This is covered by #28748