tty: stdio properties defined inside exec() child

[dusansimic]

Properties inside exec() child were not predefined because
process.stdin is a PIPE.

This commit suggests predefining them inside getStdin() function.

Fixes: #2333

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

Affected core subsystem(s)

[jasnell]

Ping @nodejs/tsc ... thoughts on this?

[cjihrig]

It seems incorrect to me to unconditionally set these like this.

[Fishrock123]

@dusansimic These are only available to tty.ReadStreams on purpose, see https://nodejs.org/dist/latest-v8.x/docs/api/tty.html#tty_class_tty_readstream

If we are going to add them more universally, they should be added to all net.Sockets, I think.

[refack]

Hello @dusansimic and welcome. Thanks for submitting this PR 🥇
If you haven't already, you might find it informative to read the CONTRIBUTING guide (especially the part about "discuss and update").

P.S. If you have any question feel free to contact me directly (@-mention me, or ping me on IRC)

[Fishrock123]

Fwiw I personally would prefer to just have these be set only on tty streams. I don't think they make much sense elsewhere.

[bnoordhuis]

Setting .isTTY etc. on all net.Socket objects is not right.

[Fishrock123]

I'm going to close this, I don't think this is the approach we are collectively going to take. Simple detection already works fine for these properties.