Grunt LESS force compile on error -

i wondering if it's possible force grunt compile less if there error?

the reason ask i'm outputting settings interface (moodle) less can changed users. when try see colour or math throws errors because it's either expecting rgba value or number value.

an example of syntax be:

div{background-color: rgba(0,0,0,~"[[setting:blockboxshadowalpha]]");} 

this works fine if put directly compiled css fails when using rgba() function or doing following:

a:hover{color: darken(~"[[setting:linkcolor]]", 20%);}