fix: contextify sourceMap

[helloyou2012]

This PR contains a:

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

Motivation / Use-Case

some loader (like postcss-loader) generate the source map with the absolute path. Cause contentHash differences on different project paths.

Breaking Changes

Additional Info

[alexander-akait]

We should not contextify source map, it should be done on css-loader side, webpack need to absolute sources

[helloyou2012]

#512

[helloyou2012]

Ref: https://github.com/webpack/webpack/blob/b7f08b42b85f89e52facac426251d26ec64f2e6d/lib/NormalModule.js#L528

[helloyou2012]

@evilebottnawi I don't think it should be done on css-loader side. Even if do it on css-loader side, it does not guarantee the other loaders contextify. So I think it should do on this plugin. Webpack is also contextify source map first and don't need to absolute sources.

[alexander-akait]

No, we need absolute sources for webpack, you break source maps, other CSS files on a page can have source maps too with relative sources (for example src/style.css)

some loader (like postcss-loader) generate the source map with the absolute path.

postcss-loader doesn't create source maps with absolute paths

[helloyou2012]

https://github.com/postcss/postcss-loader/blob/18c93f16164b875861e281c63342bd2f46ba0bf3/src/index.js#L159

[alexander-akait]

@helloyou2012 It is a bug in postcss-loader, using path.resolve is a wrong idea, without absolute sources webpack will be generate broken source maps

[helloyou2012]

path.resolve return absoluted paths.

[alexander-akait]

@helloyou2012 yep, but they may not necessarily be relatively to current process cwd

[helloyou2012]

So postcss-loader should keep the original relative path and no need resolve it?

[alexander-akait]

@helloyou2012 postcss-loader should generate right sources with absolute paths, css-loader should contextify using webpack://, webpack automatically absolute them https://github.com/webpack/webpack/blob/master/lib/SourceMapDevToolPlugin.js#L78

[helloyou2012]

why not contextify using webapck:// on this plugin?

[alexander-akait]

@helloyou2012 because this plugins should not do it

[alexander-akait]

@helloyou2012 and we still have the same problem with style-loader, so it is better to fix it on css-loader side

[helloyou2012]

Is this pr to fix this bug?
webpack-contrib/css-loader#1031

[alexander-akait]

@helloyou2012 yep, bug we need a new a PR, contextify is better solution

[codecov]

Codecov Report

Merging #533 into master will decrease coverage by 1.16%.
The diff coverage is 57.89%.

@@            Coverage Diff             @@
##           master     #533      +/-   ##
==========================================
- Coverage   88.55%   87.38%   -1.17%     
==========================================
  Files           5        5              
  Lines         428      444      +16     
  Branches       96      105       +9     
==========================================
+ Hits          379      388       +9     
- Misses         47       51       +4     
- Partials        2        5       +3     

Impacted Files	Coverage Δ
src/index.js	85.65% <57.89%> (-2.20%)	⬇️

---

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 25b0ecd...b55b2ad. Read the comment docs.

[alexander-akait]

Fixed on css-loader side (now we always pass webpack://./rootDirectory/my-style.css sources), fix for postcss-loader will be in near future

[alexander-akait]

Just update css-loader to latest version 4.2.2