postcss-normalize-whitespace

Normalize whitespace with PostCSS.

Install

With npm do:

npm install postcss-normalize-whitespace --save

h1{
    width: calc(10px - ( 100px / var(--test) )) 
}

h1{
    width: calc(10px - 100px / var(--test))
}

See the PostCSS documentation for examples for your environment.