Webpacker::Compiler swallows stdout in the event of failed compilation

[jebw]

In the event of a failed compilation Webpacker::Compiler#run_webpack will swallow the output of stdout and only show the output of stderr.

If webpack is incorrectly outputting on StdOut, as seems to be the case with a missing node module, then the user just see's a blank error with no further information

Compilation failed:

Happy to submit a patch to resolve this - not sure on the best approach? Options I can think of are

1. Extend line L71 to something like

logger.error "Compilation failed:\n#{stdout}\n#{stderr}"

2. Log the stdout to a different level in the logger

logger.error "Compilation failed:\n#{stderr}"
logger.debug "#{stdout}"

Thanks

[jakeNiemiec]

Slightly related: #1677

[botanicus]

I can confirm that this indeed occurs frequently (the last case was when I by accident declared already declared const) as well as that solutions proposed by @jebw do indeed fix it.

I'm also happy to submit patch, but don't want to steal @jebw's credit.

I suggest this to be treated as a high priority bug, because it makes webpacker pretty much useless.