feature request: expand "description" part

[trickyni]

The "description" kind seems to match every configured pattern against a secondary, hard-coded pattern that checks for the "conventional commits" syntax style.

However, being able to create custom fold texts via a simple pattern matching outside of conventional commits would be incredibly useful.

For example: I'd like to use /^##%s+(.+)/ to match individual markdown header levels, and configure each with its own custom icon and highlight pattern.

Could that be added? Either as its own "kind", or as an extension of the "description" kind?

Thank you!

EDIT: If this is doable, could there be multiple styles stemming from one pattern?
For example: if the pattern is /^#+ (.+)/, could there be multiple styles defined for different prefixes of this style, rather than having to create a whole custom type for each markdown header?
Something like

styles = {
  "/^#%s+/" = {...}
}

or

styles = {
  h2 = {
    prefix = "/^##%s+/"
    ...
  }
}

I've forked the code with a very rudimentary patch that lets me bypass the hard-coded second pattern-match, but I'm scraping at the edges of my lua know-how with the stuff I just mentioned 😅

[OXY2DEV]

Doing X -> Y is slow(as you have to match N number of patterns which makes everything slow), which is why the plugin only handles as specific type.

I have an example code which you can modify to make whichever patterns you need to add support to.

[trickyni]

The example code didn't work OOTB.
(I use vim.o.foldmethod = "expr" and vim.o.foldexpr = "v:lua.vim.treesitter.foldexpr()")

After tinkering with it (had to remove the +1 from the table.concat in the condition)
I've managed to make it render, but it only renders folded text using the "H4" icon and highlight group, and the text for every folded line is the same arbitrary line from my file.

I'd also add that the syntax for this example requires a lot more understanding of lua than what I would expect from a plugin's configuration. While I do personally enjoy the opportunity to learn some lua, I think this is worth considering.

for the sake of comparison, here's a snippet from a configuration I've managed to make work on a forked version:

        {
          kind = "description",
          condition = function()
            return vim.bo.filetype == "markdown"
          end,
          pattern = "^#%s+(.+)",
          styles = { default = { hl = "markdownH1", icon = "Ⅰ ", icon_hl = "markdownH1" } },
        },
        {
          kind = "description",
          condition = function()
            return vim.bo.filetype == "markdown"
          end,
          pattern = "^##%s+(.+)",
          styles = { default = { hl = "markdownH2", icon = "Ⅱ ", icon_hl = "markdownH2" } },
        },
        {
          kind = "description",
          condition = function()
            return vim.bo.filetype == "markdown"
          end,
          pattern = "^###%s+(.+)",
          styles = { default = { hl = "markdownH3", icon = "Ⅲ ", icon_hl = "markdownH3" } },
        },

It's certainly not elegant, and as you've pointed out- not efficient either. But the syntax is incredibly easy to read and configure.

Could there be some middle-ground to be found?

[OXY2DEV]

The example code didn't work OOTB.
(I use vim.o.foldmethod = "expr" and vim.o.foldexpr = "v:lua.vim.treesitter.foldexpr()")

That's because another style already uses that as the condition.

You can simply modify that style.

    ts_expr = {
      condition = function (_, window)
        return vim.wo[window].foldmethod == "expr" and vim.wo[window].foldexpr == "v:lua.vim.treesitter.foldexpr()";
      end,

      parts = {
        {
          kind = "bufline",
          condition = function (buffer)
            local start_line = table.concat(
              vim.fn.getbufline(buffer, vim.v.lnum)
            );

            return not string.match(start_line, "(#+)%s+(.+)$");
          end,

          delimiter = " ... ",
          hl = "@comment"
        },
        require("foldtext.examples").headings.parts[1],
      },
    }

[OXY2DEV]

It's certainly not elegant, and as you've pointed out- not efficient either. But the syntax is incredibly easy to read and configure.

Could there be some middle-ground to be found?

That depends entirely on how much should be configurable.

If it's something like adding an icon in the front based on some pattern, then simple enough.

If it's something like showing some custom text based on pattern, this method becomes messy & hard to read pretty quickly.

[trickyni]

require("foldtext").setup({
  condition = function()
    return true
  end,
  styles = {
    default = {},
    ts_expr = {
      condition = function(_, window)
        return vim.wo[window].foldmethod == "expr" and vim.wo[window].foldexpr == "v:lua.vim.treesitter.foldexpr()"
      end,
      parts = {
        {
          kind = "bufline",
          condition = function(buffer)
            local start_line = table.concat(vim.fn.getbufline(buffer, vim.v.lnum), "")
            -- return not string.match(start_line, "(#+)%s+(.+)$")
            return false
          end,
          delimiter = " ... ",
          hl = "@comment",
        },
        {
          kind = "section",
          output = function(buffer)
            local start_line = table.concat(vim.fn.getbufline(buffer, vim.v.lnum), "")
            local headings, content = string.match(start_line, "^(#+)%s+(.+)$")
            if not headings or not content then
              return { "nope", "@comment" }
            end

            ---@type { icon: string, hl: string, icon_hl?: string }[]
            local config = {
              { icon = "󰼏  ", hl = "markdownH1" },
              { icon = "󰎨  ", hl = "markdownH2" },
              { icon = "󰼑  ", hl = "markdownH3" },
              { icon = "󰎲  ", hl = "markdownH4" },
              { icon = "󰼓  ", hl = "markdownH5" },
              { icon = "󰎴  ", hl = "markdownH6" },
            }

            local heading_config = config[#headings] or config[1]

            return {
              { heading_config.icon, heading_config.icon_hl or heading_config.hl },
              { content, heading_config.hl },
            }
          end,
        },
      },
    },
  },
})

this is my foldtext config right now. (had to copy examples.header.part[1] from the file because I needed to change the highlight groups)

After completely removing the first part's condition, it "displays" the correct part, but it renders every line as a blank line.

[OXY2DEV]

but it renders every line as a blank line.

You have set default to {} so it renders nothing.

If you only plan on using 1 style move everything inside ts_expr.parts into default.

[trickyni]

That depends entirely on how much should be configurable.

If it's something like adding an icon in the front based on some pattern, then simple enough.

I would love to see any kind of syntax that enables me to match a line to a pattern, display a capture group for it, append/prepend an icon or a text string to it, and define hl groups.
Anything more than that might be cool, but I don't see myself using anything above what I've described

[OXY2DEV]

Your config can be simplified,

styles = {
    default = {
        {
          kind = "section",
          output = function(buffer)
            local start_line = table.concat(vim.fn.getbufline(buffer, vim.v.lnum), "")
            local headings, content = string.match(start_line, "^(#+)%s+(.+)$")
            if not headings or not content then
              return { "nope", "@comment" }
            end

            ---@type { icon: string, hl: string, icon_hl?: string }[]
            local config = {
              { icon = "󰼏  ", hl = "markdownH1" },
              { icon = "󰎨  ", hl = "markdownH2" },
              { icon = "󰼑  ", hl = "markdownH3" },
              { icon = "󰎲  ", hl = "markdownH4" },
              { icon = "󰼓  ", hl = "markdownH5" },
              { icon = "󰎴  ", hl = "markdownH6" },
            }

            local heading_config = config[#headings] or config[1]

            return {
              { heading_config.icon, heading_config.icon_hl or heading_config.hl },
              { content, heading_config.hl },
            }
          end,
        },
    },
    ts_expr = {
        condition = false
    },
}

[OXY2DEV]

I would love to see any kind of syntax that enables me to match a line to a pattern, display a capture group for it, append/prepend an icon or a text string to it, and define hl groups.

"match a line to a pattern" is the problematic part. You probably expect the config to look like,

{
  "^foo" = { ... },
  "bar" = { ... },
  "baz" = { ... },
}

But if a line matches both bar & baz, it would randomly pick one of them.

[trickyni]

But if a line matches both bar & baz, it would randomly pick one of them.

Wouldn't it just pick the first one that matches?

[OXY2DEV]

@trickyni nope. One of the quirks of Lua is that table key value pairs are accessed in random order(at least in Lua 5.1).

Since the pattern matching is done in a sequence, the sequence can change randomly.

[OXY2DEV]

It's dependent on the hash value of the fields of a table so it's hard to replicate & hard to debug.

One way around it is to manually sort the keys first. But this comes at the cost of needing to add ^ to keys so that they get picked up first.

[trickyni]

Incredible. absolutely incredible.
Personally I wouldn't mind taking the extra minute to make sure my patterns are all mutually-exclusive, but I can the issue haha

---

Still trying to make the simplified config work btw. It's latching the same way as the less-simplified mess, but somehow it's still returning empty lines

I'm very confused. The code seems fine, and it's clearly understanding where the headers are... Something isn't returning what it's intending to return, and I have no idea why.

[OXY2DEV]

Share the actual text. It's hard to tell the issue from a screenshot.