--stream prints newlines as \n

Expected Behavior

I run my tests with lerna run --stream test, the packages tests are simple Jest tests. The output printed by Lerna doesn’t properly renders the newlines, for instance, this is what I get:

Possible Solution

I’m not sure, but it looks like Lerna does something to escape the special characters and forgets to restore them before it prints.

Steps to Reproduce (for bugs)

1. create a package/something with inside its package.json a Jest test command
2. run lerna run --stream test in the root of the project

lerna.json

{
  "lerna": "2.1.1",
  "packages": [
    "packages/*"
  ],
  "version": "independent",
  "npmClient": "yarn"
}

lerna-debug.log

<!-- If you have a `lerna-debug.log` available, please paste it here -->
<!-- Otherwise, feel free to delete this <details> block -->

Context

This bug makes it very difficult to read the logs, especially in CI

Your Environment

Executable	Version
lerna --version	2.1.1
npm --version	5.3.0
yarn --version	1.0.0-20170815.1425
node --version	8.1.2

OS	Version
macOS	10.12.6

[ptshih]

This also happens with lerna run --parallel

[charlesbjohnson]

I also ran into this, but it seems to be an issue primarily with jest. Relevant issues:

• https://github.com/facebook/jest/issues/5064
• https://github.com/facebook/jest/issues/3690

jest’s BaseReporter writes output to stderr instead of stdout. See here.

Since lerna run collapses newlines for stderr via strong-log-transformer, we end up with escaped newlines in the output. https://github.com/lerna/lerna/blob/d35c7aa0875013248f55b26487eac99d55b59a78/src/ChildProcessUtilities.js#L52

I’m not entirely sure why this is jest’s default behavior since it doesn’t seem to be consistent with other test runners (notably mocha). As such, I think the fix probably belongs in jest and not in lerna.

Removing mergeMultiline in lerna might not break anything (--parallel?), but it seems like it could also have larger implications since lerna run is not limited to running tests.

There is a very simple workaround to perform the redirection to stdout in bash, though this still probably won’t work well with CI tools that read from stderr to determine build failures.

// /repo/packages/sub/package.json
"scripts": {
  "test": "jest 2>&1"
}

// /repo/package.json
"scripts": {
  "test": "lerna run test"
}