ClayCSS add a deep merge function

[pat270]

Sass only provides a shallow merge function, map-merge, that doesn't merge nested maps. This makes extending nested maps impossible. All properties must be redeclared when extending a nested map.

$var: (
  link: (
    hover-color: black,
  ),
);

$var: () !default;
$var: map-merge((
  color: black,
  link: (
    color: blue,
  ),
), $var);

Output: (color: black, link: (hover-color: black))
Output should be: (color: black, link: (color: blue, hover-color: black))

[duracell80]

For anyone running into compile errors with map-deep-merge. Be careful with the _clay_variables.scss file in the src of your theme. I had a $btn-link : #00558C; which was causing this error ... Error: argument $map2 of map-deep-merge($map1, $map2) must be a map.

It could happen with any variable, some of these are not namespaced or isolated enough to prevent human error.