fix(loader): source map sources and file paths

[npetruzzelli]

• Improves source map path reliability (legacy and normal)
• Fix sources and file to be URLs that are relative to the file containing the map.
  • Because of how dramatically different this is, the user must opt-in to this part of the fix by setting legacySourceMaps option to false. Making this fix the default behavior would be a breaking change requiring a new major version.

Side note: npm run test-source-map throws an error when using webpack 4.5+. I needed to install webpack 3.x for it to run correctly.

This contributes to the fixes for

• Weird source map paths when used together with css-loader #529
• Weird source map paths when used together with sass-loader css-loader#652

[jsf-clabot]

All committers have signed the CLA.

[npetruzzelli]

See also: webpack/css-loader#753

[npetruzzelli]

I'm seeing some build errors that I did not experience locally. I'll have to look have another look.

[npetruzzelli]

Looks like:

• I need to update an existing test
• I need to add additional tests to meet threshold requirements.

[alexander-akait]

No new option, please provide minimum reproducible test repo, we should fix it without new options

[alexander-akait]

Also you PR is breaking change, we can't accept this

[npetruzzelli]

@evilebottnawi - I've removed the option part of it. I still need to update the test suite and create a test repo. It may take me some time to get to it. I'll comment again once it is all in place. You may see commits trickle in in the mean time.

I believe concerns about it being a breaking change may be addressed by then, if not, I may have more questions at that time.

[codecov]

Codecov Report

Merging #602 into master will decrease coverage by 0.13%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #602      +/-   ##
==========================================
- Coverage   97.81%   97.67%   -0.14%     
==========================================
  Files           6        6              
  Lines         137      129       -8     
==========================================
- Hits          134      126       -8     
  Misses          3        3

Impacted Files	Coverage Δ
lib/loader.js	100% <ø> (ø)	⬆️
lib/normalizeOptions.js	95.83% <100%> (-0.6%)	⬇️

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[codecov]

Codecov Report

Merging #602 into master will decrease coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #602      +/-   ##
==========================================
- Coverage   97.79%   97.67%   -0.12%     
==========================================
  Files           6        6              
  Lines         136      129       -7     
==========================================
- Hits          133      126       -7     
  Misses          3        3

Impacted Files	Coverage Δ
lib/loader.js	100% <ø> (ø)	⬆️
lib/normalizeOptions.js	95.83% <100%> (-0.6%)	⬇️
lib/proxyCustomImporters.js	100% <0%> (ø)	⬆️
lib/webpackImporter.js	100% <0%> (ø)	⬆️
lib/importsToResolve.js	100% <0%> (ø)	⬆️
lib/formatSassError.js	88.88% <0%> (+0.65%)	⬆️

---

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[alexander-akait]

Close due inactivity, if you still have problem please open issue, sorry for delay