Selector only present @nested is dropped from CSS module in build

[tremby]

Description

I'm making use of the CSS nesting at-rule, which I believe is provided to us by cssnext.

I noticed some things which were working in development were broken when I built my site, and I traced it to the at-rule.

When in a CSS module, classes which only appear under a @nest are dropped during the build.

Steps to reproduce

Check out this repository, which is the basic starter with a few elements and a CSS module added.

https://github.com/tremby/gatsby-nest-bug

In particular, the test code is:

    <p className={styles.green}>green</p>
    <p className={styles.yellowbg}>yellowbg</p>
    <p className={styles.red}>red</p>
    <p className={styles.orangebg}>orangebg</p>
    <div className={styles.yellowbg}>
      <p className={styles.green}>green in yellowbg</p>
    </div>
    <div className={styles.orangebg}>
      <p className={styles.red}>red in orangebg</p>
    </div>

With CSS

.green {
  color: green;

  @nest .yellowbg & {
    background-color: yellow;
  }
}

.red {
  color: red;

  @nest .orangebg & {
    background-color: orange;
  }
}

.orangebg {}

Run it in development mode and see the output. Then build it and view again.

Expected result

both in development and when built.

Actual result

The correct result when in development, and the following when built.

The line "green in yellowbg" should be on a yellow background.

The line "red in orangebg" is working, but only because I added a stub .orangebg {} rule.

Environment

• Gatsby version (npm list gatsby): [email protected]
• gatsby-cli version (gatsby --version): 1.1.41
• Node.js version: v8.9.4
• Operating System: Linux spiral 4.4.0-112-generic Different wrappers for different content #135-Ubuntu SMP Fri Jan 19 11:48:36 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

File contents (if changed):

gatsby-config.js: not changed
package.json: not changed
gatsby-node.js: not changed
gatsby-browser.js: not changed
gatsby-ssr.js: not changed

[m-allanson]

Hey @tremby, this is strange. I'm not sure what's happening here but it sounds like a bug.

It'd be great to see a PR solving this. Check out the contributing docs if you'd like to take a crack at fixing it.

[KyleAMathews]

Due to the high volume of issues, we're closing out older ones without recent activity. Please open a new issue if you need help!

[tremby]

Hm, I'm actually not sure whether it's still relevant. @KyleAMathews, am I right that Gatsby 2 removes cssnext?

[KyleAMathews]

Yeah