Generate Sass Sourcemaps

[Harald-LB]

This PR solves Issue #71. External source maps are now generated by default along with the CSS file.

[pathawks]

This PR was errantly closed because it was based on the sassc branch, which was deleted.
I have changed the base branch to master and reopened the PR. We may need some Git-Fu to get it all synced back up properly.

[ashmaroli]

Requesting a few edits here and there..

[ashmaroli]

@DirtyF Your site should build fine now. The bug has been fixed.

[ashmaroli]

@Harald-LB Can you please add a small documentation under the heading Usage in the README for this project?
The section just needs to inform the user regarding the availability of sourcemaps and if they're able to configure the same in any way..

After this feature has been shipped, we'll update the docs for Jekyll Core accordingly.

[ashmaroli]

Thank you for the documentation @Harald-LB.
Based on that documentation, I'd like to point to some issues with this PR:

• precision and line_comments will be ignored in safe-mode
• source_map_contents defaults to true but cannot be overridden by the user.

The above two scenarios are untested and undocumented.

[Harald-LB]

@ashmaroli

precision and line_comments will be ignored in safe-mode

Can somebody explain to me what safe-mode ought to be?

source_map_contents defaults to true but cannot be overridden by the user.

I just tested, and yes ... you are right.

May be we should not set source_map_contents in line 168 of sass_configs. Or invert jekyll_sass_configuration, overrides in the call to Jekyll::Utils.deep_merge_hashes (I guess this
is what I wanted to achieve).

Or as a third alternative, just not document this option, like a number of other obscure options I did not mention (for example silent: when set, sassc will throw away all output).

[DirtyF]

sourcemaps is generated at first build, when I edit scss in devtools and save it, then an error pops:

[2019-02-21 18:45:50] ERROR `/assets/css/main.css.map' not found.

[ashmaroli]

Can somebody explain to me what safe-mode ought to be?

@Harald-LB Safe mode is that mode where chances of arbitrary code execution are minimal-to-none.
The exact principle is beyond me, and what matters here is that GitHub Pages run in such an environment. All Jekyll builds on GHP are always in the --safe mode.

The comment I made earlier was based on the current implementation:

if safe?
  overrides
...

So, yes, it is best that those two options aren't exposed in the documentation now.

If you really want source_map_contents to be configurable, then you can define a new private helper method that in turn uses jekyll_sass_configuration to determine the final value returned just like how the :style is determined for example.

[Harald-LB]

@DirtyF

sourcemaps is generated at first build, when I edit scss in devtools and save it, then an error pops:

I cannot reproduce this problem. Can you give me some more information

[Harald-LB]

@ashmaroli

Source map generation cannot be disabled as of now.

Sounds a bit frustrated.

Should I add an option no_sourcemap? It's not a big deal.

[ashmaroli]

Should I add an option no_sourcemap? It's not a big deal.

@Harald-LB If a simple false could disable source maps generation, that would be most welcome. Otherwise, no_sourcemap could do as well..
Thank you for all the work you've put into this so far.

[ashmaroli]

Couple of tests for recently added methods required.

[DirtyF]

@jekyllbot: merge + minor