- NodeJS Console initialization fix

[nowherenone]

Summary
This is a fix for the problem when NodeJS is "swallowing" console output.
BufferedConsole is initializing Console module with constructor parameters that don't match with the expected ones.

[codecov-io]

Codecov Report

Merging #4157 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master    #4157   +/-   ##
=======================================
  Coverage   60.55%   60.55%           
=======================================
  Files         196      196           
  Lines        6777     6777           
  Branches        6        6           
=======================================
  Hits         4104     4104           
  Misses       2670     2670           
  Partials        3        3

Impacted Files	Coverage Δ
packages/jest-cli/src/lib/buffered_console.js	7.69% <0%> (ø)	⬆️

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[cpojer]

Can you go into more detail of what this issue is aimed at fixing, and also providing a test that this change fixes? I don't see right now how this PR makes sense, I'll need more context. Thank you.

[nowherenone]

@cpojer Sure. I've referenced the original issue 3 days ago - Jest 20.0.0.4 swallows the console output from an app that is being tested. Here is one more issue about the same problem, and here is another one

That is really frustrating problem reported by many users, but all those issues were just closed without any fixes. So I've proposed a fix that definitely solves it.

A test that covers this update should prove that console.log calls from a tested app (not from the Jest itself) are really make output to stdout. To be honest - I don't know how to makes this test without running Jest inside of another process that logs all stdout calls from it.

[Pyrolistical]

I wrote an infinite loop and jest doesn't output to console, but this should solve my issue as well

[thymikee]

I'm fine with this change. Looks like stubbing stdout in constructor is unnecessary here. And console.logs et al. still call BufferedConsole.write

[cpojer]

Alright, not so fast. Passing process.stdout can cause the console implementation in node to write directly to the output stream which we explicitly do not want. The constructor call isn't wrong, it is intentionally pushing data into the buffered stream. If you want everything to be printed in a test that is an infinite loop, for example, use --verbose.

[nowherenone]

Well, @cpojer then I don't understand how it isn't wrong.

When you are extending Console - the first parameter of super should be a stream that takes the output. And in our case this buffered stream should bring the output to the console after all. But since there is a BufferedConsole.write call that has nothing to do with stdout - all console calls just getting pushed into this._buffer and nothing else happens after that.

So, basically, you are creating a Console, that is detached from stdout at all.

[cpojer]

The buffer gets sent back to the Jest parent process, which will print it when it prints the test result.

[nowherenone]

Thank you for the explanation, --verbose key had solved my case.
Please excuse me for the noise. :)

[github-actions]

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