How to enable nano-like whitespace highlighting in vim?

Question

nano has a useful bit of syntax highlighting that actually highlights whitespace (tabs and spaces), under two conditions: (1) the whitespace does not have a non-whitespace character between either the last character or the beginning of the line and it, and (2) that the file is source code and not plain, plain text (as in a shopping list). How can I emulate this kind of behavior in vim?

Answer 1

I use set list and set listchars in .vimrc to show tabs and trailing white spaces, you can use a condition for selective file type like this.

if !(&filetype == "txt")
  set list                " show special characters
  set listchars=tab:→\ ,trail:·,nbsp:·
endif

So my files look like this when those charaters are present.

function someFunc() { // no trailing spaces here
→   var a = "hola"; // 3 trailing spaces.···
    alert(a); // this line starts with spaces instead of tab
// next a line with 4 white spaces and nothing else
····
// next a line with a couple tabs
→   →   
}

Note: · is not .

Edit

So to answer to your comment, you can do that by adding this to your ~/.vimrc, make sure to add it after the colorscheme, or it will be hi clear'd.

if !(&filetype == "txt")
  highlight WhiteSpaces ctermbg=green guibg=#55aa55
  match WhiteSpaces /\s\+$/
endif

You can change the highlight colors and refine the regular expression as needed. /\s\+$/ will match trailing spaces or tabs and lines that contain nothing but either of those 2 characters. If you only want to highlight lines with just tabs and spaces use /^\s\+$/ instead.