feat(editorconfig): add builtin EditorConfig support

1 files changed, 246 insertions, 0 deletions

diff --git a/runtime/lua/editorconfig.lua b/runtime/lua/editorconfig.lua
new file mode 100644
index 0000000000..2079006234
--- /dev/null
+++ b/runtime/lua/editorconfig.lua
@@ -0,0 +1,246 @@
+local M = {}
+
+M.properties = {}
+
+--- Modified version of the builtin assert that does not include error position information
+---
+---@param v any Condition
+---@param message string Error message to display if condition is false or nil
+---@return any v if not false or nil, otherwise an error is displayed
+---
+---@private
+local function assert(v, message)
+  return v or error(message, 0)
+end
+
+--- Show a warning message
+---
+---@param msg string Message to show
+---
+---@private
+local function warn(msg, ...)
+  vim.notify(string.format(msg, ...), vim.log.levels.WARN, {
+    title = 'editorconfig',
+  })
+end
+
+function M.properties.charset(bufnr, val)
+  assert(
+    vim.tbl_contains({ 'utf-8', 'utf-8-bom', 'latin1', 'utf-16be', 'utf-16le' }, val),
+    'charset must be one of "utf-8", "utf-8-bom", "latin1", "utf-16be", or "utf-16le"'
+  )
+  if val == 'utf-8' or val == 'utf-8-bom' then
+    vim.bo[bufnr].fileencoding = 'utf-8'
+    vim.bo[bufnr].bomb = val == 'utf-8-bom'
+  elseif val == 'utf-16be' then
+    vim.bo[bufnr].fileencoding = 'utf-16'
+  else
+    vim.bo[bufnr].fileencoding = val
+  end
+end
+
+function M.properties.end_of_line(bufnr, val)
+  vim.bo[bufnr].fileformat = assert(
+    ({ lf = 'unix', crlf = 'dos', cr = 'mac' })[val],
+    'end_of_line must be one of "lf", "crlf", or "cr"'
+  )
+end
+
+function M.properties.indent_style(bufnr, val, opts)
+  assert(val == 'tab' or val == 'space', 'indent_style must be either "tab" or "space"')
+  vim.bo[bufnr].expandtab = val == 'space'
+  if val == 'tab' and not opts.indent_size then
+    vim.bo[bufnr].shiftwidth = 0
+    vim.bo[bufnr].softtabstop = 0
+  end
+end
+
+function M.properties.indent_size(bufnr, val, opts)
+  if val == 'tab' then
+    vim.bo[bufnr].shiftwidth = 0
+    vim.bo[bufnr].softtabstop = 0
+  else
+    local n = assert(tonumber(val), 'indent_size must be a number')
+    vim.bo[bufnr].shiftwidth = n
+    vim.bo[bufnr].softtabstop = -1
+    if not opts.tab_width then
+      vim.bo[bufnr].tabstop = n
+    end
+  end
+end
+
+function M.properties.tab_width(bufnr, val)
+  vim.bo[bufnr].tabstop = assert(tonumber(val), 'tab_width must be a number')
+end
+
+function M.properties.max_line_length(bufnr, val)
+  local n = tonumber(val)
+  if n then
+    vim.bo[bufnr].textwidth = n
+  else
+    assert(val == 'off', 'max_line_length must be a number or "off"')
+    vim.bo[bufnr].textwidth = 0
+  end
+end
+
+function M.properties.trim_trailing_whitespace(bufnr, val)
+  assert(
+    val == 'true' or val == 'false',
+    'trim_trailing_whitespace must be either "true" or "false"'
+  )
+  if val == 'true' then
+    vim.api.nvim_create_autocmd('BufWritePre', {
+      group = 'editorconfig',
+      buffer = bufnr,
+      callback = function()
+        local view = vim.fn.winsaveview()
+        vim.api.nvim_command('silent! undojoin')
+        vim.api.nvim_command('silent keepjumps keeppatterns %s/\\s\\+$//e')
+        vim.fn.winrestview(view)
+      end,
+    })
+  else
+    vim.api.nvim_clear_autocmds({
+      event = 'BufWritePre',
+      group = 'editorconfig',
+      buffer = bufnr,
+    })
+  end
+end
+
+function M.properties.insert_final_newline(bufnr, val)
+  assert(val == 'true' or val == 'false', 'insert_final_newline must be either "true" or "false"')
+  vim.bo[bufnr].fixendofline = val == 'true'
+  vim.bo[bufnr].endofline = val == 'true'
+end
+
+--- Modified version of |glob2regpat()| that does not match path separators on *.
+---
+--- This function replaces single instances of * with the regex pattern [^/]*. However, the star in
+--- the replacement pattern also gets interpreted by glob2regpat, so we insert a placeholder, pass
+--- it through glob2regpat, then replace the placeholder with the actual regex pattern.
+---
+---@param glob string Glob to convert into a regular expression
+---@return string Regular expression
+---
+---@private
+local function glob2regpat(glob)
+  local placeholder = '@@PLACEHOLDER@@'
+  return (
+    string.gsub(
+      vim.fn.glob2regpat(
+        vim.fn.substitute(
+          string.gsub(glob, '{(%d+)%.%.(%d+)}', '[%1-%2]'),
+          '\\*\\@<!\\*\\*\\@!',
+          placeholder,
+          'g'
+        )
+      ),
+      placeholder,
+      '[^/]*'
+    )
+  )
+end
+
+--- Parse a single line in an EditorConfig file
+---
+---@param line string Line
+---@return string|nil If the line contains a pattern, the glob pattern
+---@return string|nil If the line contains a key-value pair, the key
+---@return string|nil If the line contains a key-value pair, the value
+---
+---@private
+local function parse_line(line)
+  if line:find('^%s*[^ #;]') then
+    local glob = (line:match('%b[]') or ''):match('^%s*%[(.*)%]%s*$')
+    if glob then
+      return glob, nil, nil
+    end
+
+    local key, val = line:match('^%s*([^:= ][^:=]-)%s*[:=]%s*(.-)%s*$')
+    if key ~= nil and val ~= nil then
+      return nil, key:lower(), val:lower()
+    end
+  end
+end
+
+--- Parse options from an .editorconfig file
+---
+---@param filepath string File path of the file to apply EditorConfig settings to
+---@param dir string Current directory
+---@return table Table of options to apply to the given file
+---
+---@private
+local function parse(filepath, dir)
+  local pat = nil
+  local opts = {}
+  local f = io.open(dir .. '/.editorconfig')
+  if f then
+    for line in f:lines() do
+      local glob, key, val = parse_line(line)
+      if glob then
+        glob = glob:find('/') and (dir .. '/' .. glob:gsub('^/', '')) or ('**/' .. glob)
+        local ok, regpat = pcall(glob2regpat, glob)
+        if ok then
+          pat = vim.regex(regpat)
+        else
+          pat = nil
+          warn('editorconfig: Error occurred while parsing glob pattern "%s": %s', glob, regpat)
+        end
+      elseif key ~= nil and val ~= nil then
+        if key == 'root' then
+          opts.root = val == 'true'
+        elseif pat and pat:match_str(filepath) then
+          opts[key] = val
+        end
+      end
+    end
+    f:close()
+  end
+  return opts
+end
+
+--- Configure the given buffer with options from an .editorconfig file
+---
+---@param bufnr number Buffer number to configure
+---
+---@private
+function M.config(bufnr)
+  bufnr = bufnr or vim.api.nvim_get_current_buf()
+  local path = vim.fs.normalize(vim.api.nvim_buf_get_name(bufnr))
+  if vim.bo[bufnr].buftype ~= '' or not vim.bo[bufnr].modifiable or path == '' then
+    return
+  end
+
+  local opts = {}
+  for parent in vim.fs.parents(path) do
+    for k, v in pairs(parse(path, parent)) do
+      if opts[k] == nil then
+        opts[k] = v
+      end
+    end
+
+    if opts.root then
+      break
+    end
+  end
+
+  local applied = {}
+  for opt, val in pairs(opts) do
+    if val ~= 'unset' then
+      local func = M.properties[opt]
+      if func then
+        local ok, err = pcall(func, bufnr, val, opts)
+        if ok then
+          applied[opt] = val
+        else
+          warn('editorconfig: invalid value for option %s: %s. %s', opt, val, err)
+        end
+      end
+    end
+  end
+
+  vim.b[bufnr].editorconfig = applied
+end
+
+return M