Source maps do not have to be on their own line

[pond]

(NB: This PR builds on #132. I can't see a way to do a pull request on top of the prior pull request, so the diff on this one will make more sense once #132 is completed. I had to build on it since the source map removal logic of #132 is now extended further.)

While some older resources claim that source maps must be on their own line at the end of a file and while Propshaft's Regexp for this asserts such, this is not the case. Consider:

sass ./app/assets/stylesheets/application.scss ./app/assets/builds/application.css --no-source-map --style compressed --load-path=node_modules

...in package.json. This results in application.css including a source map comment in /* ... */ form at the end of the last line of minified CSS:

<very-long-line>...vertical-align:middle}/*# sourceMappingURL=application.css.map */

...noting that a terminating line feed is also present afterwards. Since this is a CSS comment appearing at the end of a line it is syntactically valid and browsers such as Chrome do read the source map. Under e.g. Propshaft 0.7.0, CSS source maps promptly break because it doesn't consider the not-on-own-line map comment to be valid.

• It seems that so long as the comment is the last thing in the file, whether on its own line or not, then it is processed
• Source map comments in the middle of the file are, as before, not processed
• The regexp is therefore updated to check for end-of-stream (\Z) rather than start-of-line (^)
• This means it might optionally capture a closing */ in comments of that form, so the internal private methods now need to be given both an opening and closing string for the comment captures
• Test coverage for JS with //# and CSS with /* ... */ style comments included

[pond]

Bump on this.

[brenogazzola]

Do you need to make any changes to this now that #132 is merged?

[pond]

@brenogazzola Thanks for the reminder - updated to resolve conflicts after merge of #132 and now ready for review.

[brenogazzola]

@pond I apologize for not merging this PR for so long. I was going to merge it now, but it seems there are conflicts again. Could you fix them, and I'll immediately merge this?

[pond]

@brenogazzola I too have been extraordinarily busy and apologies in turn for taking so long to fix the conflicts - they were a little fiddly. It's done now and CI is green. Hopefully a merge can happen before conflicts re-emerge! :-D

[pond]

@brenogazzola (bump on this, thanks...)

[brenogazzola]

@pond Thanks!

[pond]

Ah! Great. Legend. Thanks :-)