Variables in Bourbon size() mixin - css

Question

I've recently started using an updated version of the Bourbon SASS plugin. I've previously used a custom mixin to set the width and height using the following syntax;
$width: 350;
$height: 200;
.wrapper {
#include size($width $height);
}
This would assume px as the unit of measurement. However with the updated version of Bourbon, it has it's own size() mixin which doesn't work quite the same.
I cannot figure out how to use variables for the width and height properties. I've tried the following to no avail;
#include size(#{$width}px #{$height}px); - interpolation doesn't appear to work directly in the mixin. I tried doing something similar by making a new variable that had the unit on the end.
$width: 350;
$height: 200;
$width_str: #{$width}px;
$height_str: #{$height}px;
.wrapper {
#include size($width_str $height_str);
}
Finally, I tried setting the variables like this as I've used similar syntax elsewhere (albeit not for a mixin);
$width_str: ($width) + px;
$height_str: ($height) + px;
I don't get any errors when compiling the SCSS, instead the width and heigth properties are just missing from the stylesheet. I can confirm that using string values like so: #include size(350px 200px); does work, I just cannot get variables to play nice with this mixin. Any ideas?
UPDATE: While I still can't get the bourbon size mixin to work with variables, I can still use the custom one I was using previously, as long as that's defined after including bourbon in my project. For reference, this is the size mixin I use, works with everything I've ever thrown at it;
#mixin size($size) {
#if length($size) == 1 {
#if $size == auto {
width: $size;
height: $size;
}
#else if unitless($size) {
width: $size + px;
height: $size + px;
}
#else if not(unitless($size)) {
width: $size;
height: $size;
}
}
// Width x Height
#if length($size) == 2 {
$width: nth($size, 1);
$height: nth($size, 2);
#if $width == auto {
width: $width;
}
#else if not(unitless($width)) {
width: $width;
}
#else if unitless($width) {
width: $width + px;
}
#if $height == auto {
height: $height;
}
#else if not(unitless($height)) {
height: $height;
}
#else if unitless($height) {
height: $height + px;
}
}
}

Answer 1

In the code of new Bourbone library you can find the following code for the "size" mixin:
#if $height == auto or (type-of($height) == number and not unitless($height)) {
height: $height;
}
#if $width == auto or (type-of($width) == number and not unitless($width)) {
width: $width;
}
The main problem is about "unitless" function that returns:
unitless(100) => true
unitless(100px) => false
that's why you have to always pass into the mixin values such as "350px", "250px"
You can try to use the following "size" mixin%
#mixin size($size) {
$height: nth($size, 1);
$width: $height;
#if length($size) > 1 {
$height: nth($size, 2);
}
#if $height == auto or type-of($height) == number {
#if unitless($height){
height: ($height) + px;
} #else {
height: $height;
}
}
#if $width == auto or type-of($width) == number {
#if unitless($width){
height: ($width) + px;
} #else {
height: $width;
}
}
}