[Fix] Prevent build from breaking when .scss file is empty

[crhayes]

I was attempting to set up my build with SASS according to the guides. In order to get the build working as quickly as possible I created an empty app.scss file and imported it into my main module. I expected the build to complete, but instead received this error:

Not sure how you feel about this solution, but I traced the problem down to /src/Asset.js:70.

if (this.contents && this.mightHaveDependencies()) {
  await this.parseIfNeeded();
  await this.collectDependencies();
}

this.contents is equal to an empty string, therefore this check evaluates falsy and the contents are not parsed. The end result is that this.ast is not set and remains null.

Because of this, /src/SASSAsset.js:51 blows up:

generate() {
  return [
    {
      type: 'css',
      value: this.ast.css.toString() // this.ast is null
      hasDependencies: false
    }
  ];
}

EDIT:

Pushed up the same fix for LESS files.

[gnijuohz]

Just noticed the same with .less files. Do you want to fix that also? I could submit a PR to your repo if you are busy :)

[crhayes]

@gnijuohz Thanks for the heads up, I fixed it!

[codecov-io]

Codecov Report

Merging #1193 into master will increase coverage by 2.86%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1193      +/-   ##
==========================================
+ Coverage   85.59%   88.45%   +2.86%     
==========================================
  Files          77       77              
  Lines        4310     4105     -205     
==========================================
- Hits         3689     3631      -58     
+ Misses        621      474     -147

Impacted Files	Coverage Δ
src/assets/LESSAsset.js	100% <ø> (+2.12%)	⬆️
src/assets/SASSAsset.js	100% <ø> (+6.38%)	⬆️
src/assets/ReasonAsset.js	92.3% <0%> (-7.7%)	⬇️
src/transforms/babel.js	88.55% <0%> (-4.98%)	⬇️
src/assets/GLSLAsset.js	93.1% <0%> (-3.2%)	⬇️
src/utils/config.js	86.95% <0%> (-1.45%)	⬇️
src/utils/syncPromise.js	100% <0%> (ø)	⬆️
src/assets/YAMLAsset.js	100% <0%> (ø)	⬆️
src/assets/TOMLAsset.js	100% <0%> (ø)	⬆️
... and 20 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bfc1d3c...a197b41. Read the comment docs.

[gnijuohz]

@crhayes great! I was about to submit a PR to your repo haha. Thanks!

[DeMoorJasper]

You could fallback to this.contents instead of an empty string, it would end up being the same though. Might be faster as you have it right now.
Would only be really useful if ast can ever be undefined/null while content is not.