feat(folding): add configuration for folding

Author: mehalter

README.md

@@ -51,6 +51,13 @@ require("astroui").setup({
 {
   -- Colorscheme set on startup, a string that is used with `:colorscheme astrodark`
   colorscheme = "astrodark",
+  -- Configure how folding works
+  folding = {
+    -- whether a buffer should have folding can be true/false for global enable/disable or fun(bufnr:integer):boolean
+    enabled = function(bufnr) return require("astrocore.buffer").is_valid(bufnr) end,
+    -- a priority list of fold methods to try using, available methods are "lsp", "treesitter", and "indent"
+    methods = { "lsp", "treesitter", "indent" },
+  },
   -- Override highlights in any colorscheme
   -- Keys can be:
   --   `init`: table of highlights to apply to all colorschemes

lua/astroui/config.lua

@@ -29,6 +29,15 @@
 ---```
 ---@field file_icon AstroUIFileIconHighlights?
 
+---@alias AstroUIFoldingMethod
+---| "indent" # indentation based folding (`:h fold-indent`)
+---| "lsp" # LSP based folding (`:h vim.lsp.foldexpr`)
+---| "treesitter" # Treesitter based folding (`:h vim.treesitter.foldexpr`)
+
+---@class AstroUIFoldingOpts
+---@field enabled (boolean|fun(bufnr:integer):boolean)? whether folding should be enabled in a buffer or not
+---@field methods AstroUIFoldingMethod[]? a table of folding methods in priority order
+
 ---@class AstroUILazygitOpts
 ---@field theme_path string? the path to the storage location for the lazygit theme configuration
 ---@field theme table<string|number,{fg:string?,bg:string?,bold:boolean?,reverse:boolean?,underline:boolean?,strikethrough:boolean?}>? table of highlight groups to use for the lazygit theme
@@ -131,6 +140,16 @@
 ---colorscheme = "astrodark"
 ---```
 ---@field colorscheme string?
+---Configure how folding works
+---Example:
+---
+---```lua
+---folding = {
+---  enabled = function(bufnr) return require("astrocore.buffer").is_valid(bufnr) end,
+---  methods = { "lsp", "treesitter", "indent" },
+---}
+---```
+---@field folding AstroUIFoldingOpts|false?
 ---Override highlights in any colorscheme
 ---Keys can be:
 ---  `init`: table of highlights to apply to all colorschemes
@@ -218,6 +237,7 @@
 ---@type AstroUIOpts
 local M = {
   colorscheme = nil,
+  folding = {},
   highlights = {},
   icons = {},
   text_icons = {},

lua/astroui/folding.lua

@@ -6,35 +6,55 @@
 --
 -- copyright 2024
 -- license GNU General Public License v3.0
-
 local M = {}
 
+local config = require("astroui").config.folding
+
 local is_setup = false
 local lsp_bufs = {}
 
+local fold_methods = {
+  lsp = function(lnum, bufnr)
+    if lsp_bufs[bufnr or vim.api.nvim_get_current_buf()] then return vim.lsp.foldexpr(lnum) end
+  end,
+  treesitter = function(lnum, bufnr)
+    if vim.bo.filetype and vim.treesitter.get_parser(bufnr, nil, { error = false }) then
+      return vim.treesitter.foldexpr(lnum)
+    end
+  end,
+  indent = function(lnum, bufnr)
+    if not lnum then lnum = vim.v.lnum end
+    if not bufnr then bufnr = vim.api.nvim_get_current_buf() end
+    return vim.api.nvim_buf_get_lines(bufnr, lnum - 1, lnum, false)[1]:match "^%s*$" and "="
+      or math.floor(vim.fn.indent(lnum) / vim.bo[bufnr].shiftwidth)
+  end,
+}
+
 --- A fold expression for doing LSP and Treesitter based folding
 ---@param lnum? integer the current line number
 ---@return string the calculated fold level
 function M.foldexpr(lnum)
   if not is_setup then M.setup() end
   local bufnr = vim.api.nvim_get_current_buf()
-  -- only fold real file buffers
-  if not require("astrocore.buffer").is_valid(bufnr) then return "0" end
-  -- if an LSP with folding is attached us it for folding
-  if lsp_bufs[bufnr] then return vim.lsp.foldexpr(lnum) end
-  local filetype = vim.bo[bufnr].filetype
-  -- don't fold dashboards
-  if filetype:find "dashboard" then return "0" end
-  -- if filetype and a treesitter parser exists, use treesitter for folding
-  if filetype and vim.treesitter.get_parser(bufnr, nil, { error = false }) then return vim.treesitter.foldexpr(lnum) end
-  -- fallback to indentation based folding
-  if not lnum then lnum = vim.v.lnum end
-  return vim.fn.getline(lnum):match "^%s*$" and "=" or math.floor(vim.fn.indent(lnum) / vim.bo[bufnr].shiftwidth)
+  -- check if folding is enabled
+  local enabled = config and config.enabled
+  if type(enabled) == "function" then enabled = enabled(bufnr) end
+  if enabled then
+    for _, method in ipairs(config and config.methods or {}) do
+      local fold_method = fold_methods[method]
+      if fold_method then
+        local fold = fold_method(lnum, bufnr)
+        if fold then return fold end
+      end
+    end
+  end
+  -- fallback to no folds
+  return "0"
 end
 
 function M.setup()
   -- TODO: remove check when dropping support for Neovim v0.10
-  if vim.fn.has "nvim-0.11" == 1 then
+  if vim.lsp.foldexpr then
     local augroup = vim.api.nvim_create_augroup("astroui_foldexpr", { clear = true })
     vim.api.nvim_create_autocmd("LspAttach", {
       desc = "Monitor attached LSP clients with fold providers",