Place a string onto the command line without execution

Question

Suppose I have a variable

let g:f_themes="./themes/**"

Suppose I want to map this command to a key:

:execute "vimgrep /".expand("<cword>")."/g ".g:f_themes." | copen"

That works, even though it may complain about not finding <cword>. I can deal with that.

But what if I want to instead place that string onto the command line and NOT execute it, which allows me to inspect and edit the command before hitting <cr>. I can't use :execute because it will go ahead and execute. And I can't get the value of g:f_themes to expand to ./themes/** if I just type the command without the :execute.

Is there a way to place a string onto the command line so that a simple <cr> would go ahead and execute the line?

Answer 1

You can insert the evaluations of expressions into the command-line (or a buffer) with the expression register, by pressing Ctrl-R=. You can also use this in a mapping:

nnoremap <leader>gt :vimgrep /<C-R>=expand("<cword>")<CR>/g <C-R>=g:f_themes<CR> <bar> copen

See :help quote_= for more details on the expression register and :help c_CTRL-R for specific notes on using it in command-line mode.

EDIT: You mention in a comment that you'd like to be able to do this without any mapping being involved. You can use feedkeys() for this:

:call feedkeys(':vimgrep /' . expand("<cword>") . '/g ' . g:f_themes . ' | copen')

This can be run from the command-line, or directly within a function (that has not been invoked by a mapping).

Answer 2

I think I got part of the answer: how to map a key to do this.

First, declare this one-line function (1):

exe "function! Temp(cword) \n return ':vimgrep /'.a:cword.'/ '.g:f_themes.' | copen' \n endfunction"

Then do this key mapping (2):

:nnoremap <expr> <Leader>gt ':'.Temp(expand("<cword>"))

It puts this on the command line:

:vimgrep /mycword/ ./themes/** | copen

Just what I wanted.

A couple of points: (1): You can't use bars (|) to separate lines in a compressed function. (2): You need <expr>. Learn something new every day. You need to quote the :. You need to use expand(). Or it won't work. I don't know if Temp() could directly refer to <cword>.

But now there is another question. What if one wanted to pump the command line directly from a function. Is it possible to do that?