Is this required to use Bootstrap mixins? - asp.net-mvc

Question

I'm new to LESS and Bootstrap and I'm confused at the outcome of my css file.
My basic goal is to use the mixins and variables in bootstrap in my own css files.
From my understanding the process would be, get the less files, import them into the project, and import the bootstrap reference. So at this point I can now use the mixins in my own css file.
Example:
#import "less/bootstrap.less";
.myRow{
.make-row();
}
However now I have a 7400+ lines of styling in myCustomStyles.css. Is this "correct"? I don't understand why it actually imports all the styles. My understanding is... that I have a reference to bootstrap.min.css CDN or local. Then myCustomStyles.css will be included AFTER that and override the default values.
I guess I'm confused at how do I take advantage of a CDN and still use the mixins and variables in bootstrap?
I've used the following two articles as a reference:
http://www.helloerik.com/bootstrap-3-less-workflow-tutorial
http://www.codeproject.com/Articles/594098/How-to-customize-Twitter-Bootstrap-to-fit-your-web

Answer 1

Bootstrap.less is the full bootstrap implementation. It is going to have all the variables and mixins to build the entire CSS for bootstrap. If you don't want this, then you should probably pick and choose which LESS files to include instead. You probably want variables and mixins, so you could maybe get by with only importing variables.less and mixins.less?
If you look at bootstrap.less it looks like this:
// Core variables and mixins
#import "variables.less";
#import "mixins.less";
// Reset
#import "normalize.less";
#import "print.less";
// Core CSS
#import "scaffolding.less";
#import "type.less";
#import "code.less";
#import "grid.less";
#import "tables.less";
#import "forms.less";
#import "buttons.less";
// snip...
It is nothing but a bunch of imports to other .less files. Each file is sort of specific to what it is doing. At a minimum I think you would need variables and possibly mixins. Normalize does a CSS reset. Grid defines the grid classes, etc.

Answer 2

Possible Since LESS 1.5
You can specify that you want the code only as a reference like so:
#import (reference) "less/bootstrap.less";
.myRow{
.make-row();
}
The addition of the (reference) tells LESS to import it by not compile the code to CSS. This allows you to use the entirety of bootstrap for mixin reference purposes, but avoids adding all the code in. Of course, one needs to know how this may affect the implementation, as there are parts of bootstrap that expect certain code to be in place to work properly. But that this a whole other thing.