Support || operator for variables

[jamie-pate]

Adds || (boolean or) operator

allows conditional overriding of variable values

@someVariable:red;
@include "otherfile.less"
=================contents of "otherfile.less"=========
@someVariable : @someVariable || green;

[lukeapage]

I am wondering whether this is best suited as an an operator or a function?

also your pull request includes 2 commits from a different release

@MatthewDL @Synchro are you happy for me to close and add a feature request for a function or do you like this?

[matthew-dean]

What's the use case here? To assign a value only if another LESS file hasn't been imported?

Note also that, in this example, @someVariable are both executed in the same scope, so it can't be redefined in this way and refer to itself. It's clear that the author is interpreting LESS more like JavaScript than CSS. So, overall, this has a number of problems which don't feel sufficiently addressed.

[Synchro]

I don't think it's especially useful (why not just set the colour right?), but I think it's another fudge for the lack of conditional structures.

[matthew-dean]

A mixin guard can actually do this, I believe.

[lukeapage]

Yes a guard can do this.. the use case for me is user set theme variables..
if you want to keep one definition of a color and then fallback on a
default.. using mixin guards ends up with a lot of code just to set a
variable.

Yes, its needed because less doesn't have control structures.. having a
function or operator is a declarative way of keeping the same functionality.

But I think the operator is messy.. I prefer a function.

[lukeapage]

closing as we all agree operator is not the way to go