Refactor loader's code

[goganchic]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

I want to make the code of the plugin a bit easier to understand and debug by removing unnecessary hidden connection between index.js and loader.js and changing variables and functions names to a bit more clear variants.

Breaking Changes

Additional Info

[jsf-clabot]

All committers have signed the CLA.

[alexander-akait]

Please accept CLA and fix linting errors, thanks

[goganchic]

@evilebottnawi would you please tell me how can I reproduce failing tests locally? I've ran npm run test and all tests passes:

--------------------------|----------|----------|----------|----------|-------------------|
File                      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
--------------------------|----------|----------|----------|----------|-------------------|
All files                 |    88.64 |    80.89 |    88.46 |    88.47 |                   |
 src                      |    88.93 |    82.24 |    88.14 |    88.71 |                   |
  CssDependency.js        |      100 |      100 |      100 |      100 |                   |
  cjs.js                  |      100 |      100 |      100 |      100 |                   |
  index.js                |    88.51 |    82.61 |     87.8 |    88.17 |... 11,531,538,560 |
  loader.js               |    88.57 |    81.58 |     87.5 |    88.57 |... 71,175,185,200 |
 src/hmr                  |    87.88 |       78 |    89.47 |    87.88 |                   |
  hotModuleReplacement.js |    87.88 |       78 |    89.47 |    87.88 |... 01,162,200,202 |
--------------------------|----------|----------|----------|----------|-------------------|

Test Suites: 5 passed, 5 total
Tests:       42 passed, 42 total
Snapshots:   19 passed, 19 total
Time:        4.386s
Ran all test suites.

What should I do to reproduce this failure https://github.com/webpack-contrib/mini-css-extract-plugin/pull/448/checks?check_run_id=221075652 (I've tried node v8.9.1)

And one more question: you have said about linter error: https://github.com/webpack-contrib/mini-css-extract-plugin/pull/448/checks?check_run_id=221075432 it's about npm audit. Should I update eslint-utils package in this PR?

[alexander-akait]

Problem in lint https://dev.azure.com/webpack-contrib/mini-css-extract-plugin/_build/results?buildId=846&view=logs&jobId=3a559e2a-952e-58d2-b8db-2e604a9266d7, ignore this problem, all are ok

[goganchic]

@evilebottnawi should I fix something else for merge this PR or everything is fine and we just need to wait for contributors?

[alexander-akait]

@goganchic wait other contributors

[sokra]

Looks good

[codecov]

Codecov Report

Merging #448 into master will decrease coverage by 0.14%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master     #448      +/-   ##
==========================================
- Coverage   88.32%   88.17%   -0.15%     
==========================================
  Files           4        5       +1     
  Lines         411      406       -5     
  Branches       86       86              
==========================================
- Hits          363      358       -5     
  Misses         46       46              
  Partials        2        2

Impacted Files	Coverage Δ
src/index.js	87.24% <ø> (-0.78%)	⬇️
src/CssDependency.js	100% <100%> (ø)
src/loader.js	89.01% <88.88%> (-0.41%)	⬇️

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[goganchic]

@evilebottnawi @sokra I've updated eslint-utils as npm audit required and have made several small refactoring-like changes. So now all checks are successful. I think PR is ready for merge.

[alexander-akait]

Thanks!