misc: get LH_ROOT via new file root.js

[connorjclark]

Replaces all the LH_ROOT = '../../../' madness with const {LH_ROOT} = require('../../../root.js'). This does a few things:

• Can just type LH_ROO+<enter> to auto-import this value to a file
• Statically verified (no more doing directory calculus to know how many levels up to go) (is this only hard for me?)
• Prepares the way for ☂️ Convert to ES modules #12689 (getting the directory of current file is no longer as simple as __dirname, so having the code in one place means less future boilerplate)

Beyond changing all instances of LH_ROOT = ..., I also grokked for lines that use __dirname to form a path that goes to the root, and changed them to use LH_ROOT.

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I did not modify any files that use __dirname w/o crossing over the root directory (ex: report-assets.js does __dirname + '/renderer/util.js')–I have some ideas for that, maybe worth discussing here:

1. could have a function getRelativePathEsm(importMeta, ...pathSegments) (usage: getRelativePathEsm(import.meta, 'somefile.json'))
2. root.js could also export all the top-level directories (LH_CORE, LH_CLI, etc...)
3. could just use LH_ROOT for everything, and have all paths used in code be relative to root

( the motivation is to avoid this code everywhere https://stackoverflow.com/a/50052194/2788187 )

[adamraine]

Any chance we can use module aliases?

[connorjclark]

module aliases

WARNING: This module should not be used in other npm modules since it modifies the default require behavior! It is designed to be used for development of final projects i.e. web-sites, applications etc.

[brendankenny]

this looks good, but I'm not a huge fan of root.js, especially if it grows to have dirname/filename substitutes. I don't have a better suggestion than my pretty bad module-utils.js one, though.