Use Neoformat for `formatexpr`

[alecandido]

I would like to do more or less the opposite of https://github.com/sbdchd/neoformat/issues/36, i.e. use Neoformat as formatexpr, such that when I select some text and press gq it gets formatted as if I issued :Neoformat, but without a custom mapping.

I'd need a function to invoke, possibly passing parameters available to formatexpr:

          The v:lnum  variable holds the first line to be formatted.
          The v:count variable holds the number of lines to be formatted.
          The v:char  variable holds the character that is going to be
                        inserted if the expression is being evaluated due to
                        automatic formatting.  This can be empty.  Don't insert
                        it yet!

I believe it should be possible just setting formatexpr in my configurations, but I'm not familiar with Neoformat internals, that's why I'm asking for help.

[sbdchd]

Hmm I think it's tricky because a lot of the underlying formatters don't support that sort of thing

[alecandido]

But :Neoformat is already able to format a visual selection. What is available to the command that would not be available while invoking through formatexpr.

For the time being, I just mapped gQ on :Neoformat (with the effect of shadowing Ex mode on Neovim), but now I have two formatters, and in most situations I'd only need a single one.

[iamFIREcracker]

@AleCandido: you can give the following a try (I have been using it for months without much problem):

function! NeoformatExpr() abort " {{{
    " if v:char != ''
    "     return
    " endif
    let line1 = v:lnum
    let line2 = v:lnum + v:count - 1
    execute ':' . line1 . ',' . line2 . 'Neoformat'
endfunction "}}}

PS. to enable it, just run setl formatexpr=NeoformatExpr() inside the filetype specific autogroup.

[alecandido]

Thanks, that is exactly what I had in mind (the concept, I was completely missing the implementation)