feat: add rollup option to export styles

[morewry]

See #451 for more information.

This pull request adds a styleExport option to modular-css-rollup that will add an additional ES Module export of each CSS Module's styles for CSS-in-JS approaches that may need the style contents instead of or in addition to class names and values.

One specific example is gaining true style scoping by using Shadow DOM where only styles within the shadow tree will apply to the elements in the shadow tree. Making the styles available in scripts allows a developer to embed the styles as a templated part of each Web Component instance.

[codecov]

Codecov Report

Merging #453 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #453      +/-   ##
==========================================
+ Coverage      99%   99.01%   +0.01%     
==========================================
  Files          31       31              
  Lines         800      810      +10     
  Branches      124      128       +4     
==========================================
+ Hits          792      802      +10     
  Misses          8        8

Impacted Files	Coverage Δ
packages/rollup/rollup.js	98.86% <100%> (+0.12%)	⬆️
packages/core/processor.js	100% <100%> (ø)	⬆️

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[tivac]

On my phone but this looks like a good start! I'll investigate the source map issue a bit, hopefully it's straightforward.

[morewry]

If the configuration map: false is used in tandem, the source map is suppressed, if map: { inline: false }, it's made external. It'd be easy to clean the snapshot up by doing one or the other, but I didn't want to muddy what the test was really testing. And it illustrates the potential gotcha: you should probably not use the same configurations re: source maps for dev and production builds.

Depending on how far you want to go with protecting users from their own mistakes, I think an implementation solution could lie in conditional defaults. Meaning, e.g. if options.styleExport then options.map.inline = false--unless the user has otherwise specified.

[tivac]

Yeah, if you define styleExport it should:

• Disable emitting CSS files to disk
• Disable usage of done
• Disable source maps unless explicitly set

Because none of those really make sense in this context.

[tivac]

Ugh, sorry. Screwed up by accidentally merging master into your pr branch. It should still land fine, the history in this PR is just uglier than necessary. Gonna see if I can fix it...

[TravisBuddy]

Hey @morewry,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

[morewry]

FYI, I have on my list to iterate on the rest of the behavior changes within the next few days.

[tivac]

@morewry I added all the ones mentioned in #453 (comment) in commit 4b67b7b, are there others?

[morewry]

Oh! I missed that! Awesome, no, that looks like everything. Thank you so much!