chore(gatsby): upgrade null-loader

[beliayeu]

Description

see #22409

Related Issues

Fixes #22409

[pieh]

There are few breaking changes on the way - https://github.com/webpack-contrib/null-loader/blob/master/CHANGELOG.md

Will have to wait for #22400 to be able to use v3 of null-loader (because right now we have 8.0 support still)

[beliayeu]

@pieh, as an option null-loader can be upgraded to v2 since v2 contains the fix for the problem I encountered and per my understanding v2 is node 8 compatible. btw, is there a better pattern how to exclude assets from build? lets assume there is a css file imported by a component, we want to include this file while in gatsby develop but exclude it during gatsby build

[pieh]

@pieh, as an option null-loader can be upgraded to v2 since v2 contains the fix for the problem I encountered and per my understanding v2 is node 8 compatible.

We do plan to drop Node 8 tomorrow - we worked out most of CI problems today (but there can be delays), so if you are fine with holding to this PR a bit longer we can keep null-loader@3. The note was as much for you as much for anyone else checking this PR after me ;)

is there a better pattern how to exclude assets from build? lets assume there is a css file imported by a component, we want to include this file while in gatsby develop but exclude it during gatsby build

This is probably best way to do this, but I'm pretty confused about aplying null-loader just for build step. You ultimately do have to add styles somehow to your site?

[beliayeu]

We do plan to drop Node 8 tomorrow - we worked out most of CI problems today (but there can be delays), so if you are fine with holding to this PR a bit longer we can keep null-loader@3

sounds great. I am totally fine

This is probably best way to do this, but I'm pretty confused about aplying null-loader just for build step. You ultimately do have to add styles somehow to your site?

the styles are added in gatsby-browser.js and in components. we have some styles that are needed only while we are in gatsby develop (styles needed for admin ui), that is why I was looking for a way how to exclude those admin styles from static build

[pieh]

the styles are added in gatsby-browser.js and in components. we have some styles that are needed only while we are in gatsby develop (styles needed for admin ui), that is why I was looking for a way how to exclude those admin styles from static build

not ideal, but you probably could try something like this (pretty sure import syntax won't work with conditional like that, that's why it's require):

if (process.env.BUILD_STAGE !== `build-javascript`) {
  require(`./layout.css`)
}

We use similar thing in gatsby ( https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby/cache-dir/public-page-renderer.js )

[pieh]

Just note, that I don't think we document BUILD_STAGE "env var" (it's not really env var, it's using webpack's DefinePlugin), so this is not really part of public API

[pieh]

Thanks! node 8 was just dropped so we can go ahead with this