It is not possible to properly set $link-color variable in user-land config.

[dilame]

In your _variables.scss

$link-color:                theme-color("primary") !default;

Your docs (https://getbootstrap.com/docs/4.1/getting-started/theming/#variable-defaults) says

However, when overriding across Sass files, your overrides must come before you import Bootstrap’s Sass files.

But it is impossible to just change $key for theme-color() function, before import _variables.scss, because theme-color expects $theme-colors that declared in _variables.scss.
It turns out a vicious circle.
I know i can just use a variable instead of function call, but it is a bit confusing. Why you use theme-color("primary") instead of just $primary?

[XhmikosR]

@MartijnCuppens can you confirm?

[MartijnCuppens]

The theme-color function is a bit redundant indeed. I will check to what extent we can simplify this.

[MartijnCuppens]

In my opinion we can deprecate the theme-color, gray, color functions. The color and gray functions are not used by Bootstrap and it's easy to remove the theme-color dependency.

@mdo, what do you think?

[mdo]

We could potentially remove those come v5? The maps are primarily meant for looping over, but I'm unsure how much we rely on the functions we introduced with them.

[retan]

Using $primary here is not an option either.
This code

$link-color:                $primary;

Throws an error: Error: Undefined variable: "$primary".
It's the same problem. If the custom _variables.scss is included before bootstrap, the SASS won't let you use undefined variable.

[dilame]

I define $primary in my own variables.scss, and it is not dirty.
But define the whole $theme-colors map and include functions just to redefine $link-color is redundant.

[retan]

Of course typically you would define your own value for $primary. But the same problem occurs with many other variables. Eg. I wanted to assign $body-color: $gray-700 (instead the default $gray-900). To do that I need to declare that $gray-700 variable in my file (though I want it to have te same value as the defaults).
I think at least the docs should clarify this.

[flexjoly]

I dont like to see these functions to disappear. Because then we need to make a separate variable for each color.
We just adopted the method of using the functions for colors and not the variables. We add colors to the maps, without making a separate var for it.

We dont use the theme-color function.... I mapped the theme-colors with the colors. So we just use color() and gray().

I found this discussion because I wanted to ask if gray() could be changed so it would accept integers and strings both. Like: gray('100') and gray(100). At the moment gray(100) returns null :-(

So please keep gray() and color(). Although if they are removed, I will add them via our own sass-functions.
What if bootstrap removes the separate vars and uses the functions? Seems more DRY to me.

Greetz, flexjoly