Make source map files generated correctly.

[AlbertXingZhang]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

  Bug Fix

• What is the current behavior? (You can also link to an open issue here)

  The generated source map file for main.bundle.js only contains the following incorrect content.

{"version":3,"sources":[],"names":[],"mappings":"","file":"initial.css","sourceRoot":""}

• What is the new behavior (if this is a feature change)?

  The whole source mappings will be produced properly.

• Other information:

  Plugin overwrites source maps generated by other plugins webpack-contrib/extract-text-webpack-plugin#119

[nnixaa]

Hi @AlbertXingZhang, could you provide a bit more details, I just pulled your changes locally and see no difference, could you point me out on what I'm missing?

[AlbertXingZhang]

Hi @nnixaa,

For example, in production environment the webpack produces main bundle javascript file (like main.d1226f060c4abdb58c79.bundle.js) with its source map file (like main.d1226f060c4abdb58c79.bundle.map). But the source map file is wrong. It has been overwritten by ExtractTextPlugin. In order to get correct source mappings for the javascript file, the trick is using [file] for sourceMapFilename config. You can find more detailed discussions at webpack-contrib/extract-text-webpack-plugin#119.

Here are the source map files generated before and after this patch.

[nnixaa]

Awesome, thanks @AlbertXingZhang