A simple but useful tool, which hook the npm bin from #!/usr/bin/env node to #!/usr/bin/env node --inpect --debug-brk. Then the process could be started with support of attaching to the VS Code debugger.
Tested in macOS, maybe compatible with Linux, but not Windows.
$ npm i -g hookdebug
Usage: hkd <bin> [bin options]
Debug yarn:
$ hookd yarn
Debug roadhog build:
$ hookd roadhog build
Debug npm -h
$ hookd npm -h