Case Study: Grep Operator, Part Three
Our shiny new "grep operator" is working great, but part of writing Vimscript is being considerate and making your users' lives easier. We can do two more things to make our operator play nicely in the Vim ecosystem.
By yanking the text into the unnamed register we destroy anything that was previously in there.
This isn't very nice to our users, so let's save the contents of that register before we yank and restore it after we've done. Change the code to look like this:
nnoremap <leader>g :set operatorfunc=GrepOperator<cr>g@ vnoremap <leader>g :<c-u>call GrepOperator(visualmode())<cr> function! GrepOperator(type) let saved_unnamed_register = @@ if a:type ==# 'v' normal! `<v`>y elseif a:type ==# 'char' normal! `[v`]y else return endif silent execute "grep! -R " . shellescape(@@) . " ." copen let @@ = saved_unnamed_register endfunction
We've added two
let statements at the top and bottom of the function. The
first saves the contents of
@@ into a variable and the second restores it.
Write and source the file. Make sure it works by yanking some text, then
<leader>giw to run our operator, then pressing
p to paste the text
you yanked before.
When writing Vim plugins you should always strive to save and restore any settings or registers your code modifies so you don't surprise and confuse your users.
Our script created a function named "GrepOperator" in the global namespace. This probably isn't a big deal, but when you're writing Vimscript it's far better to be safe than sorry.
We can avoid polluting the global namespace by tweaking a couple of lines in our code. Edit the file to look like this:
nnoremap <leader>g :set operatorfunc=<SID>GrepOperator<cr>g@ vnoremap <leader>g :<c-u>call <SID>GrepOperator(visualmode())<cr> function! s:GrepOperator(type) let saved_unnamed_register = @@ if a:type ==# 'v' normal! `<v`>y elseif a:type ==# 'char' normal! `[v`]y else return endif silent execute "grep! -R " . shellescape(@@) . " ." copen let @@ = saved_unnamed_register endfunction
The first three lines of the script have changed. First, we modified the
function name to start with
s: which places it in the current script's
We also modified the mappings and prepended the
GrepOperator function name
<SID> so they could find the function. If we hadn't done this they would
have tried to find the function in the global namespace, which wouldn't have
grep-operator.vim script is not only extremely useful,
but it's also a considerate Vimscript citizen!
Treat yourself to a snack. You deserve it!