In bug 1352968 part 8, we try to construct CSSOM object for @import rules when possible. But there are cases that we cannot construct the object correctly, those cases include: 1. when the stylesheet is a clone, its child sheet list may not be rebuilt correctly (bug 1367213) 2. when the newly inserted child sheet is a clone from an existing sheet, but the Servo side @import rule struct is holding an independent stylesheet (bug 1368381) When those bugs are fixed, we should be able to always return non-null object for @import rule, and also change several warnings added in bug 1352968 to assertions.

I'm not getting a properly constructed import rule in this simple case, either. Not sure if it's the same bug: <style type='text/css'> @import url('foo.css') </style> <script type="text/javascript">document.write(document.styleSheets[0].cssRules[0])</script> (It prints null in Stylo)

(In reply to Manish Goregaokar [:manishearth] from comment #1) > I'm not getting a properly constructed import rule in this simple case, > either. Not sure if it's the same bug: > > <style type='text/css'> @import url('foo.css') </style> > <script > type="text/javascript">document.write(document.styleSheets[0].cssRules[0])</ > script> > > (It prints null in Stylo) This is a new bug unrelated to existing two. Thanks for mentioning. Filed bug 1371488 and submitted patch there.

This should be all be fixed by emilio's patch in bug 1372041.