How can I use Tabularize to align by spaces, but ignore spaces in end-of-line comments?

Question

Simple question: I might have content formatted like

item1 item2 # this is a comment
longer_name1 foobarbaz # another comment

that I want to see aligned as follows:

item1        item2     # this is a comment
longer_name1 foobarbaz # another comment

and notice the spaces in the comments are not matched or aligned. How can I do this?

Answer 1

I solved this problem and wanted to share with everyone: just takes a little regex-magic to match the first space after non-whitespace text, except where it is preceded by a comment character anywhere in the line.

In short, you can place these lines in your .vimrc:

vnoremap <expr> -<Space> ':Tabularize /\S\(' . split(&commentstring, '%s')[0] . '.*\)\@<!\zs\ /l0<CR>'
nnoremap <expr> -<Space> ':Tabularize /\S\(' . split(&commentstring, '%s')[0] . '.*\)\@<!\zs\ /l0<CR>'

Note we can detect the filetype comment-character by parsing &commentstring (try :echo &commentstring to see what it looks like). You can also replace that call to split() as follows

vnoremap <expr> -<Space> ':Tabularize /\S\(' . b:NERDCommenterDelims['left'] . '.*\)\@<!\zs\ /l0<CR>'
nnoremap <expr> -<Space> ':Tabularize /\S\(' . b:NERDCommenterDelims['left'] . '.*\)\@<!\zs\ /l0<CR>'

if you happen to use the NERDCommenter plugin.

---

Came across a great example of where this is useful today: case statements in bash scripts -- so the following

case "$string" in
  foo) command ;; # here's a command
  foobarbaz) longer_command ;; # and another one
  abcdef) f ;; # the last command
  *) hello ;; # and the default case
esac

becomes

case "$string" in
  foo)       command        ;; # here's a command
  foobarbaz) longer_command ;; # and another one
  abcdef)    f              ;; # a final command
  *)         hello          ;; # default case
esac

note again that the spaces in end-of-line comments are ignored.