Fix for sourcemap file locations

[chrisnicola]

babel-loader was setting options.sourceFileName to a relative path, but this does not seem to work correctly anymore with either webpack or babel itself and causes incorrect source map file data in webpack.

Setting it to an absolute path seems to fix the problem.

Fixes #480 and possibly also #93.

[danez]

can you please revert this. lib is correct.

[chrisnicola]

Ah I see, because the build script outputs to /lib. I mainly made this change so I could install from my git branch for testing and didn't really think about it.

That may also explain why it isn't working with Node <8.0. I still have to do some testing of this today, but I'll revert that.

[chrisnicola]

It looks like using a proper build tarball fixed my issues and everything is working again. Thanks for that.

[michael-ciniawsky]

map.sourceRoot should be empty
options.filename === this.resourcePath right ? (map.filename is ignored)
Are there any possible sources? If, they would need to be absolute paths :)

map.sources = map.sources.map((src) => path.resolve(src))

[chrisnicola]

@michael-ciniawsky I'm unclear what you're referring to. Do you mean this shouldn't be assigned to process.cwd()? https://github.com/chrisnicola/babel-loader/blob/38ed9a3db991a3f098d48f1e4ac734dc6d74fc15/src/index.js#L124

[michael-ciniawsky]

According to @sokra sourceRoot should be '' and webpack itself takes care of it. Note that I ask for postcss-loader (CSS), so it might vary here, definitely needs triage, but process.cwd() seem to be odd :)

[chrisnicola]

@michael-ciniawsky you are correct that sourceRoot doesn't need to be set. However for the absoluteResourcePath to not simple return the filename the sourceFileName must be set to options.filename

At least that's what my testing showed.

@danez is there anything else I need to do for this PR?

[chrisnicola]

@danez are any other changes required for this.

@michael-ciniawsky I've tested this and it does work with sourceRoot set to '' or unset, but it still requires that the sourceFileName be set to the absolute path of the file. It doesn't seem to matter what the sourceRoot is set to.

[chrisnicola]

@danez hey I'm sure your busy, so I'd be happy to take care of any work necessary to get this merged in. Is there anything I can do?

[chrisnicola]

Still hoping to see this merged sometime. Right now we are packaging the fix manually to make sure source maps work.