Less v3.0.0 incorrectly processes a base64-encoded style sheets

If you compile the following code:

@import url("data:text/css;base64,Ym9keSB7IGJhY2tncm91bmQtY29sb3I6IGxpbWUgIWltcG9ydGFudDsgfQ==");

then get the following error:

FileError: 'data:text/css;base64,Ym9keSB7IGJhY2tncm91bmQtY29sb3I6IGxpbWUgIWltcG9ydGFudDsgfQ==' wasn't found. Tried - data:text/css;base64,Ym9keSB7IGJhY2tncm91bmQtY29sb3I6IGxpbWUgIWltcG9ydGFudDsgfQ==,C:\temp\data:text\css;base64,Ym9keSB7IGJhY2tncm91bmQtY29sb3I6IGxpbWUgIWltcG9ydGFudDsgfQ==,C:\temp\node_modules\data:text\css;base64,Ym9keSB7IGJhY2tncm91bmQtY29sb3I6IGxpbWUgIWltcG9ydGFudDsgfQ== in C:\temp\test.less on line 1, column 1:
1 @import url("data:text/css;base64,Ym9keSB7IGJhY2tncm91bmQtY29sb3I6IGxpbWUgIWltcG9ydGFudDsgfQ==");

[matthew-dean]

This was a bug actually. See #2955 for more details.

Right. So the fact it worked in 2.7.3 was actually a bug, probably just because the “css” string was indata:text/css. There is no supported/documented method to do imports in Less in this way. If you want to preserve an @import statement, you need to specify the import type as (css).

[seven-phases-max]

The fact that this works proves that the degree of compatibility is really high.

It is, otherwise it would not be declared as a CSS superset. Still 1000 incompatibilities (of infinite language feature combinations in total) is a myriad. (It does not mean you’ll ever face more than two or three of them though. Just like most of average users will never face @import url("data:text/css;base64,Ym...).

Could you name a couple please?

A quick walk through issues here could give some ideas (it’s too tedious to build a list for even two or three when each sounds like

“Parser ignores strings at an unknown at-rule prelude (thus failing at { and ; there)”

or longer).