neovim/scripts/gen_filetype.lua

local do_not_run = true
if do_not_run then
  print([[
    This script was used to bootstrap the filetype patterns in runtime/lua/vim/filetype.lua. It
    should no longer be used except for testing purposes. New filetypes, or changes to existing
    filetypes, should be ported manually as part of the vim-patch process.
  ]])
  return
end

local filetype_vim = "runtime/filetype.vim"
local filetype_lua = "runtime/lua/vim/filetype.lua"

local keywords = {
  ["for"] = true,
  ["or"] = true,
  ["and"] = true,
  ["end"] = true,
  ["do"] = true,
  ["if"] = true,
  ["while"] = true,
  ["repeat"] = true,
}

local sections = {
  extension = { str = {}, func = {} },
  filename = { str = {}, func = {} },
  pattern = { str = {}, func = {} },
}

local specialchars = "%*%?\\%$%[%]%{%}"

local function add_pattern(pat, ft)
  local ok = true

  -- Patterns that start or end with { or } confuse splitting on commas and make parsing harder, so just skip those
  if not string.find(pat, "^%{") and not string.find(pat, "%}$") then
    for part in string.gmatch(pat, "[^,]+") do
      if not string.find(part, "[" .. specialchars .. "]") then
        if type(ft) == "string" then
          sections.filename.str[part] = ft
        else
          sections.filename.func[part] = ft
        end
      elseif string.match(part, "^%*%.[^%./" .. specialchars .. "]+$") then
        if type(ft) == "string" then
          sections.extension.str[part:sub(3)] = ft
        else
          sections.extension.func[part:sub(3)] = ft
        end
      else
        if string.match(part, "^%*/[^" .. specialchars .. "]+$") then
          -- For patterns matching */some/pattern we want to easily match files
          -- with path /some/pattern, so include those in filename detection
          if type(ft) == "string" then
            sections.filename.str[part:sub(2)] = ft
          else
            sections.filename.func[part:sub(2)] = ft
          end
        end

        if string.find(part, "^[%w-_.*?%[%]/]+$") then
          local p = part:gsub("%.", "%%."):gsub("%*", ".*"):gsub("%?", ".")
          -- Insert into array to maintain order rather than setting
          -- key-value directly
          if type(ft) == "string" then
            sections.pattern.str[p] = ft
          else
            sections.pattern.func[p] = ft
          end
        else
          ok = false
        end
      end
    end
  end

  return ok
end

local function parse_line(line)
  local pat, ft
  pat, ft = line:match("^%s*au%a* Buf[%a,]+%s+(%S+)%s+setf%s+(%S+)")
  if pat then
    return add_pattern(pat, ft)
  else
    local func
    pat, func = line:match("^%s*au%a* Buf[%a,]+%s+(%S+)%s+call%s+(%S+)")
    if pat then
      return add_pattern(pat, function() return func end)
    end
  end
end

local unparsed = {}
local full_line
for line in io.lines(filetype_vim) do
  local cont = string.match(line, "^%s*\\%s*(.*)$")
  if cont then
    full_line = full_line .. " " .. cont
  else
    if full_line then
      if not parse_line(full_line) and string.find(full_line, "^%s*au%a* Buf") then
        table.insert(unparsed, full_line)
      end
    end
    full_line = line
  end
end

if #unparsed > 0 then
  print("Failed to parse the following patterns:")
  for _, v in ipairs(unparsed) do
    print(v)
  end
end

local function add_item(indent, key, ft)
  if type(ft) == "string" then
    if string.find(key, "%A") or keywords[key] then
      key = string.format("[\"%s\"]", key)
    end
    return string.format([[%s%s = "%s",]], indent, key, ft)
  elseif type(ft) == "function" then
    local func = ft()
    if string.find(key, "%A") or keywords[key] then
      key = string.format("[\"%s\"]", key)
    end
    -- Right now only a single argument is supported, which covers
    -- everything in filetype.vim as of this writing
    local arg = string.match(func, "%((.*)%)$")
    func = string.gsub(func, "%(.*$", "")
    if arg == "" then
      -- Function with no arguments, call the function directly
      return string.format([[%s%s = function() vim.fn["%s"]() end,]], indent, key, func)
    elseif string.match(arg, [[^(["']).*%1$]]) then
      -- String argument
      if func == "s:StarSetf" then
        return string.format([[%s%s = starsetf(%s),]], indent, key, arg)
      else
        return string.format([[%s%s = function() vim.fn["%s"](%s) end,]], indent, key, func, arg)
      end
    elseif string.find(arg, "%(") then
      -- Function argument
      return string.format([[%s%s = function() vim.fn["%s"](vim.fn.%s) end,]], indent, key, func, arg)
    else
      assert(false, arg)
    end
  end
end

do
  local lines = {}
  local start = false
  for line in io.lines(filetype_lua) do
    if line:match("^%s+-- END [A-Z]+$") then
      start = false
    end

    if not start then
      table.insert(lines, line)
    end

    local indent, section = line:match("^(%s+)-- BEGIN ([A-Z]+)$")
    if section then
      start = true
      local t = sections[string.lower(section)]

      local sorted = {}
      for k, v in pairs(t.str) do
        table.insert(sorted, {[k] = v})
      end

      table.sort(sorted, function(a, b)
        return a[next(a)] < b[next(b)]
      end)

      for _, v in ipairs(sorted) do
        local k = next(v)
        table.insert(lines, add_item(indent, k, v[k]))
      end

      sorted = {}
      for k, v in pairs(t.func) do
        table.insert(sorted, {[k] = v})
      end

      table.sort(sorted, function(a, b)
        return next(a) < next(b)
      end)

      for _, v in ipairs(sorted) do
        local k = next(v)
        table.insert(lines, add_item(indent, k, v[k]))
      end
    end
  end
  local f = io.open(filetype_lua, "w")
  f:write(table.concat(lines, "\n") .. "\n")
  f:close()
end