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So, context: I'd like to use foldexpr to fold by indentation, but including the start and end lines (that are not indented). For example:

function TestFunction(args)
    statements
    ...
end

Would be entirely replaced by the fold text, which I have configured to place an ellipsis between the first and last lines, for example:

function TestFunction(args) ... end

I can achieve this using :lua vim.opt.foldexpr = "max([indent(v:lnum+1), indent(v:lnum), indent(v:lnum-1)])/&tabstop", but with this solution, adjacent functions are merged into one fold, for example (with fold values shown in the first column):

0 local variable = 7
1 function SayHello()
1     print("hello!")
1 end
1 function SayGoodbye()
1     print("goodbye!")
1 end

Gets folded to function SayHello() ... end, completely hiding SayGoodbye(). After reading the manual page for fold-expr, I found that returning >n and <n will start and end fold level n respectively, after which I tried using:

vim.opt.foldexpr = "indent(v:lnum+1) > indent(v:lnum) ? '>' . (indent(v:lnum+1)/&tabstop) : (indent(v:lnum-1) > indent(v:lnum) ? '<' . (indent(lnum-1)/&tabstop) : indent(v:lnum)/&tabstop)"

Sorry for the disgusting expression, it's essentially saying: "if the next line is more indented then start a fold, or if the previous line is more indented then end a fold, otherwise just use indent". However, this just excludes the last line from each fold, e.g.

function Test() ... last statement
end

I'm not sure if this is just how <n works, or if I've made a mistake. Is it even possible to differentiate between adjacent folds on the same level? If anyone has any advice I'd love to hear it! My current options are as follows:

vim.opt.foldexpr = "indent(v:lnum+1) > indent(v:lnum) ? '>' . (indent(v:lnum+1)/&tabstop) : (indent(v:lnum-1) > indent(v:lnum) ? '<' . (indent(lnum-1)/&tabstop) : indent(v:lnum)/&tabstop)"
vim.opt.foldtext = "repeat(' ', indent(v:foldstart)) . trim(getline(v:foldstart)) . ' ... ' . trim(getline(v:foldend))"

This is my first post on a forum like this so I apologize if it's terribly written/formatted and missing info. Please let me know where I've messed up if need be.

1 Answer 1

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Solved, turns out I'm just stupid because <n and >n work fine. If anyone else has a similar issue, this code worked for me and can probably be adapted into a one-line expression pretty easily:

function! FX()
    if indent(v:lnum+1) > indent(v:lnum)
        return '>' . (indent(v:lnum+1)/&tabstop)
    elseif indent(v:lnum-1) > indent(v:lnum)
        return '<' .  (indent(v:lnum-1)/&tabstop)
    else
        return (indent(v:lnum)/&tabstop)
    endif
endfunction

set foldmethod=expr
set foldexpr=FX()

(The original poster is me before I made an account)

3
  • We might be able to link the accounts. Saving for follow-up. In the meantime, have you considered leaving a blank line between functions?
    – D. Ben Knoble
    Sep 10, 2023 at 22:51
  • I did think about it, but I mostly just wanted to see if it was possible. I did end up getting it very close to how I wanted, but sadly the method I was using it consistently update folds with foldexpr (zx on InsertLeave) would open all the folds whenever they updated, so I kinda gave up.
    – Sneez
    Sep 12, 2023 at 5:42
  • See vi.stackexchange.com/help/merging-accounts
    – D. Ben Knoble
    Sep 12, 2023 at 12:36

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