Fix yarn list --json stdOut parsing. fixes #388

[asprouse]

What did you implement:

Closes #388

How did you implement it:

Yarn outputs a JSON lines to represent it's output when using the --json flag. This PR simply parses each line and looks for the correct tree JSON line and passes it to the convertTrees step.

How can we verify it:

Run tests or run a build that's using yarn the extra lines are alway output if yarn needs to install anything.

Todos:

• Write tests
• Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[asprouse]

Sorry had to fixup this PR a few times and had to temporarily disable prettier from .lintstaged because of #515

[asprouse]

All rebased on master and ready to review

[HyperBrain]

Sorry for the delay, but finally I got time to review the changes completely.
There might be one issue which changes the behavior of the parsing: If you pass an invalid JSON, previously it rejected with an error and stopped. Now you return null and the deployment will continue but without dependencies, eventually leading to a broken service.
Is this intended, or is there a specific reason for the behavior?

[asprouse]

@HyperBrain The JSON parsing is now line by line and some lines may be blank which causes a parsing error. It's be possible to change the code to filter out these blank lines before parsing and to throw on invalid json. I'm fine with either approach if you prefer one over the other. I think that more important point you raise is that we should be throwing a more meaningful error if we cannot find a line where line.type === 'tree' whether this is due to parsing errors or a yarn API change. I am happy to update the PR.

[miguel-a-calles-mba]

Looks okay to me.