Lerna bootstrap swallows stdout and stderr output from NPM client

When running lerna bootstrap, any output (e.g., logs, warnings, errors) from the underlying NPM client are swallowed. This results in failed bootstraps without knowing the reason the underlying client exited with a non-zero status code. Also, warnings like misconfigured peer dependencies are never displayed to the end user.

Expected Behavior

Running lerna bootstrap should pass through output from the underlying NPM client.

Current Behavior

lerna bootstrap swallows all output from the underlying NPM client.

Possible Solution

If it’s not desired to make lerna bootstrap more verbose, perhaps only stderr can be let pass through and stdout can be enabled by adding a new --npm-client-stdout flag?

Steps to Reproduce (for bugs)

1. Set up a Lerna project using lerna init
2. Create a new package using lerna create
3. Add a non-existent dependency to the newly created package’s package.json
4. Run lerna bootstrap

lerna.json

{
  "lerna": "2.9.0",
  "version": "independent",
  "npmClient": "yarn"
}

Context

I’m managing private packages in a monorepo and often there are issues with local dependencies not being resolved by the underlying NPM client. lerna bootstrap fails silently without a clear indication of what the error is.

Your Environment

Executable	Version
lerna --version	3.20.2
npm --version	6.4.1
yarn --version	1.18.0
node --version	10.14.2

OS	Version
macOS Catalina	10.15.3

[djvs]

👍 Stuck investigating random hangs for the last hour with no solution to see where npm install is hanging.

[frosas]

Looking at the code couldn’t see any user option that could change that behavior.

If you need to troubleshoot bootstrap issues I’d suggest to temporarily replace that stdio = "pipe" for a stdio = "inherit":

https://github.com/lerna/lerna/blob/a47fc294393a3e9507a8207a5a2f07648a524722/utils/npm-install/npm-install.js#L17

@evocateur would you accept a PR making inherit the default?