Invalid media query merge of MQs inside @import with MQ

[hparra]

Tested with 1.4.2 RELEASE and 1.5.0-wip 6fe1174

A media query in a LESS file imported using import with a media query results in an invalid query.

import-test-f.less

@media screen and (min-device-pixel-ratio: 2) {
  #css {
    color: purple;
  }
}

import.less

@import "import/import-test-f" screen and (max-width: 604px);

The expected output is

@media screen and (max-width: 604px) and (min-device-pixel-ratio: 2) {
  #css {
    color: purple;
  }
}

but instead we have

@media screen and (max-width: 604px) and screen and (min-device-pixel-ratio: 2) {
  #css {
    color: purple;
  }
}

which is an invalid media query. [http://www.w3.org/TR/css3-mediaqueries/#syntax]

Furthermore, in 1.4.2 we have an empty media query with just max-width. This is no longer appearing in the 1.5.0-wip commit above.

Coincidently, the original test fails in 1.4.2 despite the fact that bin/lessc itself outputs the expected CSS. This seems to have been corrected in 1.5.0-wip as well.

[hparra]

Issue #1502 may be related.

Down to hack. I just need advice on where in the tree I should be looking.

[lukeapage]

Hi,

1.    Furthermore, in 1.4.2 we have an empty media query with just max-width. This is no longer appearing in the 1.5.0-wip commit above.
   

If this is a bug, please can you report it seperately, sounds like it needs fixing

To fix this, in the following code,

        // Trace all permutations to generate the resulting media-query.
        //
        // (a, b and c) with nested (d, e) ->
        //    a and d
        //    a and e
        //    b and c and d
        //    b and c and e
        this.features = new(tree.Value)(this.permute(path).map(function (path) {
            path = path.map(function (fragment) {
                return fragment.toCSS ? fragment : new(tree.Anonymous)(fragment);
            });

            // look at path and remove duplicate entries

            for(i = path.length - 1; i > 0; i--) {
                path.splice(i, 0, new(tree.Anonymous)("and"));
            }

            return new(tree.Expression)(path);
        }));

see comment I've added // look at path and remove duplicate entries

[lukeapage]

I will accept a pull request for this

[hparra]

Ran into this again. In general MQs within MQs only work in ideal case.

I tried fixing this months ago when I first reported issue but realized it was not trivial. Path needs to be re-parsed as it is not currently saved in a useful manner that would allow easy merging. It ended up being a can of worms.

Please let me know if someone will look at this, or if the tree will change significantly.