From:  Paul Irish <paul.irish@gmail.com>
Date:  08 Jun 2013 03:35:28 Hong Kong Time
Newsgroup:  news.mozilla.org/mozilla.dev.js-sourcemap
Subject:  

Re: Change sourceMappingURL comment syntax to avoid IE JS conditional compilation issues

NNTP-Posting-Host:  63.245.216.66

To conclude this successful thread....

*Impetus*
//@ sourceMappingURL was found to have a conflict with IE whenever it was
found in the page after //@cc_on was interpreted to turn on conditional
compilation in the IE JScript engine. A legacy version of the HTML5 Shiv is
one particular offender here.

*Spec Change*
The //@ sourceMappingURL syntax is defined in the Sourcemap V3 spec:
https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit#heading=h.lmz475t4mvbx
It was changed there to use //# syntax instead.

*sourceURL*
//@ sourceURL is also defined in the spec and was made to match the //#
syntax for consistency. For details on what it does, see:
http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/#toc-sourceurl

It's used by Ember's minispade, google's concatenate.js, and others.

*Implementation in Browser DevTools = done!*

   - *Safari Inspector* now supports //# for sourceMappingURL and sourceURL
   - *Firebug's* change has
landedfor
sourceURL.
   - *Firefox* is about to
landthe change
for sourceMappingURL. sourceURL ticket
   here .
   - *Chrome* *DevTools* landed the
changefor sourceMappingURL
and sourceURL. It will also warn about use of the
   deprecated //@ syntax.


\o/