Expanding variables in path

Question

Background

I work a lot in the twig template language, and make use of path variables. For example, an include might look like

{% include "@my_path_var/my_folder/my-template.twig" %}

The @my_path_var is shorthand for a full filesystem path, e.g. /Users/me/Sites/project/twig/patterns/.

Desire

I would like to be able to follow these paths using gf.

Question

Is there a way to enable this behavior, using Vim's native path variables, or some other Vim configuration? Or would this need to be a plugin?

Thanks.

Answer 1

gf and CTRL-W_F are able to search for path under directories listed in &path variable. Alas, I suspect that @my_path_var is some kind of variable related to your current twig (?) project.

Vim can't understand it natively. It has no idea @my_path_var means something, nor what it means (for what we know, it could have been %var%, {var}, @@var@@...)

So, you'll have to implement your own version of gf.

1. parse the line under the cursor, either with expand('<cfile>)', or analyse the result of expand('<cWORD>') if the first doesn't return something that can be exploited because of the @

2. split the path obtained to extract the @varname part, resolve it to build the finalpathname

3. and eventually open if with exe 'e '.finalpathname or anything more advanced that'll reuse windows already opened (I have such a function in lh-vim-lib)

---

EDIT:

As @Peter suggested (I did completely forget about that), we don't need to define a new mapping. We just have to set the options 'includeexpr' -- and 'include' which is not mandatory to answer the need you've expressed

As I'm the lazy kind of guy regarding option evaluation, I'd use a function from my toolbox library:

" To be defined in a ~/.vim/ftplugin/twig.vim file

" First we specify how include lines are recognized
setlocal inc={\%\ include

" then, we specify how variables are evaluated
setlocal includeexpr=substitute(v:fname,'\\v\\@(\\k+)','\\=lh\#option\#get(submatch(1))','g')

Note: this version, doesn't properly notifies when a pathname isn't found: the call to lh#option#get() should be encapsulated to throw something if lh#option#is_unset(lh#option#get(......)) evaluates to true. A simplified version could be defined with something like:

" to be defined in ~/.vim/autoload/my/twig.vim
function my#twig#get_var(name) abort " untested!
    let scopes = filter([b:, g:, t:], 'has_key(v:val, a:name)')
    if empty(scopes)
        throw "No variable named '".a:name. "' known in b:, g:, nor t:"
    endif
    return scopes[0][a:name]
endfunction

For visual modes mappings, I can't find anything with :h v_CTRL-W_f, yet it seems to work correctly. In case this is an artefact of my configuration, visual mode mappings could be defined with:

" edit the buffer in the current window, 
" or jump to the first window where the buffer is already displayed
xnoremap <silent> gf <c-\><c-n>:call lh#buffer#jump(
           \ substitute(lh#visual#selection(), '\v\@(\k+)', '\=lh#option#get(submatch(1))', 'g'), 
           \ 'e')<cr>

xnoremap <silent> <c-w>f <c-\><c-n>:call lh#buffer#jump(
           \ substitute(lh#visual#selection(), '\v\@(\k+)', '\=lh#option#get(submatch(1))', 'g'), 
           \ 'sp')<cr>

xnoremap <silent> <c-w>v <c-\><c-n>:call lh#buffer#jump(
           \ substitute(lh#visual#selection(), '\v\@(\k+)', '\=lh#option#get(submatch(1))', 'g'), 
           \ 'vert sp')<cr>

Last thing, you'll then need a way to define your variables in the scope of your current project.