The all option is broken when using stdout: 'ignore' or stderr: 'ignore'

[ehmicky]

When using the following options:

• all: true
• Either stdout: 'ignore' or stderr: 'ignore' (not both)

Then:

• result.all is correct
• But both result.stdout and result.stderr are empty

The reason is the following. The all option creates childProcess.all, which is usually a PassThrough that reads from both childProcess.stdout and childProcess.stderr. However, with the above conditions, childProcess.all is a reference for either childProcess.stdout or childProcess.stderr instead. This means result.all and result.stdout|stderr read the exact same stream.

We use get-stream, which does readable.read() calls under the hood. When result.all is reading the stream, those chunks are gone, and result.stdout|stderr cannot read them anymore. In other words, result.all and result.stdout|stderr are not sharing the stream, they are competing for it.

On the other hand, when using a PassThrough, things work for the following reason: it relies on listening for data events, which does allow sharing the stream with multiple consumers (as opposed to readable.read()).

This bug was introduced by #646. Our existing tests were missing this specific case. So we need to revert that PR, which is done by #703.