feat(source-maps): bundling improvements

[dima-v]

multiple fixes to source maps:

• fixes offset problems caused by:
  • prepended scripts;
  • duplicate dependency main module;
• remove sourece map file comments;
• add EOL separator for the anonymous module wrapper;

closes #659, related to #624

[CLAassistant]

All committers have signed the CLA.

[simonfox]

@dima-v have been discussing this with @JeroenVinke over on Gitter...couple of queries

1. what was the reason for modifying the determination of the source root
2. why the columnOffset calculation is moved to apply to all files

Below is @JeroenVinke comment with details...

I found one issue though, when I tried to use aurelia-configuration with these changes.
It looked like this:

The index.ts, aurelia-configuration.ts and deep-extend.ts should not be in the src directory, so I dug into the code.
The variables here have the following values:
aurelia-configuration
/node_modules/aurelia-configuration/dist/amd
/node_modules/aurelia-configuration
Thus the source root is set to /node_modules/aurelia-configuration. If we look at the sourcemap, this one then the sources are defined as ../../src/aurelia-configuration.ts, so when the sourceRoot is node_modules/aurelia-configuration then Chrome will think that those sources belong in the src folder.
So I changed the code to:

if (sourceMap !== null) {
  let sourceRoot = parsedPath.dir.substring(process.cwd().length);
  sourceMap.sourceRoot = sourceRoot.replace(/\\/g, '\/');
}

and that fixed it. Then it works perfectly. I'd like to know the reason for changing this code though, and how I can reproduce the issue that you had so I can confirm the fix.
Much thanks!
If you could explain the issues that you've had for which you changed those two bits of code (the offsets) and the sourceRoot, then that would help me a lot

[dima-v]

@JeroenVinke thank you for your suggestion on how to fix the source root issue.
It works for us and I updated the pull request with related changes.

Regarding to the column offset calculation ...

with the following configuration for a bundle file:

• prepend files or/and dependency package with resources (such as html, css or js files)

we found that resulting map file for the bundle will have incorrect mapping and will cause unpredictable behavior when debugging. The offset needs to consider all files in the bundle, not just those which have a sourcemap associated.

we used that tool http://sokra.github.io/source-map-visualization/#custom to find the issue.

Please let me know if you need a working example.

[JeroenVinke]

Thanks for the quick response @dima-v. Nice work