Why doesn't phpstorm compile less to css if there are variables in the file?

Question

css

Good day,
Prepared for compilation in File Watcher according to the instructions :
Installed less globally via npm and locally via bower, set the path to bin: /usr/bin/lessc in Program ,
Checked immediate file immediate file synchronization
File type - less Checkbox Create output file from stdout Working Directory - $FileDir$
- default Arguments --no-color $FileName$ Scope - Project Files Output paths to refresh - $FileNameWithoutExtension$.css Show Console - Error The problem is this:





Less files with content like:

body{
     height:100%;
    p{
       color: red;
    }
}

They compile to CSS , but if there are variables in the Less file code, then the CSS file is overwritten (((
Why is this possible?