+1.

After reading npm ls code, and isaacs/read-installed, it seems to me I should add a fourth argument to readInstalled:

function readInstalled (folder, depth, env, cb) {
...
}

Because readInstalled does not have access to npm.config.get("production").
And when doing npm ls --production it does not trigger NODE_ENV=production.

Or I could re-read (already done in readInstalled), package.json and filter readInstalled on devDependencies.

1. Fourth argument to readInstalled?
2. Read package.json from npm ls and filter?

Maybe this issue can close by #7413

yep