Lerna: stderr output is ignored if a `run` script does not fail

Created on 26 Jul 2019 · 3Comments · Source: lerna/lerna

Tasks that succeed or tasks that fail with --no-bail enabled simply discard stderr output. This output is important and discarding it can make figuring out what is happening in running tasks very difficult.

https://github.com/lerna/lerna/blob/master/commands/run/index.js#L167

Expected Behavior

stderr is reported for successful tasks.

Current Behavior

stderr is only logged if a task fails.

Possible Solution

Always log stderr in the above linked method.

Steps to Reproduce (for bugs)

Create an npm script test that logs to stdout and stderr while returning a 0 exit code
lerna run test
Notice that stderr is not output

Your Environment

| Executable | Version |
| ---: | :--- |
| lerna --version | 3.15.0 |
| node --version | v10.13.0 |

Source

nomcopter

Most helpful comment

The change in the linked PR is strictly to the batched mode. I agree it doesn't mean it's an error, but frequently it contains useful information (at least in my repo) and the lack of it makes it really hard to debug when I run scripts across my 50+ packages.

The biggest failure mode for me is when I want to run all of the tests in my repo and then review all the failures (common after a big framework change). Then I'll use lerna run test --no-bail so that I don't have to run lerna run test over and over again. However, all of the useful errors are sent to stderr, which is then dropped when --no-bail is present.

nomcopter on 26 Jul 2019

👍3

All 3 comments

Messages sent to stderr does not mean the process encountered an error. That's what process.exitCode/process.exit(code) is for.

Well-behaved CLI programs emit logging to stderr, which is generally extremely noisy and can become almost worthless in a parallel execution that lerna often creates.

If you _want_ this situation, it seems like you're really looking for --stream (add --concurrency 1 --no-prefix to reduce the interleaving, maybe).