Set variable within condition - css

Question

I need to set variable in LESS based on conditions.
#body-background-color: black;
#post-background-color: white;
#post-stacked-effect: true;
.content-padding() when ( #body-background-color = #post-background-color ) and not (#post-stacked-effect = true){
#content-padding: 0px;
}
.content-padding() when not (#body-background-color = #post-background-color), (#post-stacked-effect = true) {
#content-padding: 20px;
}
body {
.content-padding();
content: "#{post-stacked-effect}";
padding: #content-padding;
background-color: #body-background-color;
.post {
background-color: #post-background-color;
}
.some-math {
margin: -#content-padding -#content-padding #content-padding;
}
}
#content-padding is always 0px. Can you please help me fix that condition?

Answer 1

Its a bug in PHP Less Compiler. I have to do PHP workaround.
When I'm preparing variables for that compile i added function which calculates the padding in php and inject it into LESS.
Its only one row in PHP.
$lessvars["content-padding"] =
( $lessvars["body-background-color"] == $lessvars["post-background-color"] &&
!filter_var($lessvars["post-stacked-effect"], FILTER_VALIDATE_BOOLEAN) )
? "0px" : "20px";

Answer 2

You are creating a new scope with the 'when' guarded mixin which isn't visible outside.
So this isn't even supposed to work, and certainly isn't a bug.
You can instead create a function and call that from the 'when'.
#body-background-color: black;
#post-background-color: white;
#post-stacked-effect: true;
body {
.padding(#padding)
{
padding: #padding;
.some-math
{
margin: #padding + 2em;
}
}
& when ( #body-background-color = #post-background-color ) and not (#post-stacked-effect = true){
.padding(0px);
}
& when not (#body-background-color = #post-background-color), (#post-stacked-effect = true) {
.padding(20px);
}
}
I've removed the irrelevant css, and renamed it because stackoverflow formats hyphenated function names weirdly.