Improve flexibility around vendored librariesmain

compat53 is vendored since #1757 as it is required to run luarocks with lua 5.1 or 5.2.

However, this introduced some issues as the GNUmakefile install rule places these in the same place where `luarocks install compat53` would install them. This means you get conflicts if you install the actual package:
```
Warning: /.../prefix/share/lua/5.1/compat53/init.lua is not tracked by this installation of LuaRocks. Moving it to /.../prefix/share/lua/5.1/compat53/init.lua~
Warning: /.../prefix/share/lua/5.1/compat53/module.lua is not tracked by this installation of LuaRocks. Moving it to /.../prefix/share/lua/5.1/compat53/module.lua~
Warning: /.../prefix/share/lua/5.1/compat53/file_mt.lua is not tracked by this installation of LuaRocks. Moving it to /.../prefix/share/lua/5.1/compat53/file_mt.lua~
```

It is also not ideal for linux package maintainers to include a vendored package, see: https://github.com/luarocks/luarocks/pull/1757#issuecomment-3409873412.

To solve these issues, this patchset makes the following changes:
- GNUmakefile now places the compat53 files under `luarocks/vendor/compat53` (which is added internally to the luarocks script's `package.path`). This way a user's installation of compat53 does not interfere at all with luarocks one.
- Added `--with-system-compat53` option to configure script for external packaging systems.
- Fixed install.bat's logic for deciding whether to vendor compat53, as the current script includes it for every version.

install.bat already places luarocks sources outside of LUAPATH, so that part can stay as is.

I've also inverted the version check to avoid the need for future patches like: #1850.

1 files changed, 2103 insertions, 0 deletions

diff --git a/vendor/argparse.lua b/vendor/argparse.lua
new file mode 100644
index 00000000..2c2585dd
--- /dev/null
+++ b/vendor/argparse.lua
@@ -0,0 +1,2103 @@
+-- The MIT License (MIT)
+
+-- Copyright (c) 2013 - 2018 Peter Melnichenko
+--                      2019 Paul Ouellette
+
+-- Permission is hereby granted, free of charge, to any person obtaining a copy of
+-- this software and associated documentation files (the "Software"), to deal in
+-- the Software without restriction, including without limitation the rights to
+-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+-- the Software, and to permit persons to whom the Software is furnished to do so,
+-- subject to the following conditions:
+
+-- The above copyright notice and this permission notice shall be included in all
+-- copies or substantial portions of the Software.
+
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+-- FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+-- COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+-- IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+-- CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+local function deep_update(t1, t2)
+   for k, v in pairs(t2) do
+      if type(v) == "table" then
+         v = deep_update({}, v)
+      end
+
+      t1[k] = v
+   end
+
+   return t1
+end
+
+-- A property is a tuple {name, callback}.
+-- properties.args is number of properties that can be set as arguments
+-- when calling an object.
+local function class(prototype, properties, parent)
+   -- Class is the metatable of its instances.
+   local cl = {}
+   cl.__index = cl
+
+   if parent then
+      cl.__prototype = deep_update(deep_update({}, parent.__prototype), prototype)
+   else
+      cl.__prototype = prototype
+   end
+
+   if properties then
+      local names = {}
+
+      -- Create setter methods and fill set of property names.
+      for _, property in ipairs(properties) do
+         local name, callback = property[1], property[2]
+
+         cl[name] = function(self, value)
+            if not callback(self, value) then
+               self["_" .. name] = value
+            end
+
+            return self
+         end
+
+         names[name] = true
+      end
+
+      function cl.__call(self, ...)
+         -- When calling an object, if the first argument is a table,
+         -- interpret keys as property names, else delegate arguments
+         -- to corresponding setters in order.
+         if type((...)) == "table" then
+            for name, value in pairs((...)) do
+               if names[name] then
+                  self[name](self, value)
+               end
+            end
+         else
+            local nargs = select("#", ...)
+
+            for i, property in ipairs(properties) do
+               if i > nargs or i > properties.args then
+                  break
+               end
+
+               local arg = select(i, ...)
+
+               if arg ~= nil then
+                  self[property[1]](self, arg)
+               end
+            end
+         end
+
+         return self
+      end
+   end
+
+   -- If indexing class fails, fallback to its parent.
+   local class_metatable = {}
+   class_metatable.__index = parent
+
+   function class_metatable.__call(self, ...)
+      -- Calling a class returns its instance.
+      -- Arguments are delegated to the instance.
+      local object = deep_update({}, self.__prototype)
+      setmetatable(object, self)
+      return object(...)
+   end
+
+   return setmetatable(cl, class_metatable)
+end
+
+local function typecheck(name, types, value)
+   for _, type_ in ipairs(types) do
+      if type(value) == type_ then
+         return true
+      end
+   end
+
+   error(("bad property '%s' (%s expected, got %s)"):format(name, table.concat(types, " or "), type(value)))
+end
+
+local function typechecked(name, ...)
+   local types = {...}
+   return {name, function(_, value) typecheck(name, types, value) end}
+end
+
+local multiname = {"name", function(self, value)
+   typecheck("name", {"string"}, value)
+
+   for alias in value:gmatch("%S+") do
+      self._name = self._name or alias
+      table.insert(self._aliases, alias)
+      table.insert(self._public_aliases, alias)
+      -- If alias contains '_', accept '-' also.
+      if alias:find("_", 1, true) then
+         table.insert(self._aliases, (alias:gsub("_", "-")))
+      end
+   end
+
+   -- Do not set _name as with other properties.
+   return true
+end}
+
+local multiname_hidden = {"hidden_name", function(self, value)
+   typecheck("hidden_name", {"string"}, value)
+
+   for alias in value:gmatch("%S+") do
+      table.insert(self._aliases, alias)
+      if alias:find("_", 1, true) then
+         table.insert(self._aliases, (alias:gsub("_", "-")))
+      end
+   end
+
+   return true
+end}
+
+local function parse_boundaries(str)
+   if tonumber(str) then
+      return tonumber(str), tonumber(str)
+   end
+
+   if str == "*" then
+      return 0, math.huge
+   end
+
+   if str == "+" then
+      return 1, math.huge
+   end
+
+   if str == "?" then
+      return 0, 1
+   end
+
+   if str:match "^%d+%-%d+$" then
+      local min, max = str:match "^(%d+)%-(%d+)$"
+      return tonumber(min), tonumber(max)
+   end
+
+   if str:match "^%d+%+$" then
+      local min = str:match "^(%d+)%+$"
+      return tonumber(min), math.huge
+   end
+end
+
+local function boundaries(name)
+   return {name, function(self, value)
+      typecheck(name, {"number", "string"}, value)
+
+      local min, max = parse_boundaries(value)
+
+      if not min then
+         error(("bad property '%s'"):format(name))
+      end
+
+      self["_min" .. name], self["_max" .. name] = min, max
+   end}
+end
+
+local actions = {}
+
+local option_action = {"action", function(_, value)
+   typecheck("action", {"function", "string"}, value)
+
+   if type(value) == "string" and not actions[value] then
+      error(("unknown action '%s'"):format(value))
+   end
+end}
+
+local option_init = {"init", function(self)
+   self._has_init = true
+end}
+
+local option_default = {"default", function(self, value)
+   if type(value) ~= "string" then
+      self._init = value
+      self._has_init = true
+      return true
+   end
+end}
+
+local add_help = {"add_help", function(self, value)
+   typecheck("add_help", {"boolean", "string", "table"}, value)
+
+   if self._help_option_idx then
+      table.remove(self._options, self._help_option_idx)
+      self._help_option_idx = nil
+   end
+
+   if value then
+      local help = self:flag()
+         :description "Show this help message and exit."
+         :action(function()
+            print(self:get_help())
+            os.exit(0)
+         end)
+
+      if value ~= true then
+         help = help(value)
+      end
+
+      if not help._name then
+         help "-h" "--help"
+      end
+
+      self._help_option_idx = #self._options
+   end
+end}
+
+local Parser = class({
+   _arguments = {},
+   _options = {},
+   _commands = {},
+   _mutexes = {},
+   _groups = {},
+   _require_command = true,
+   _handle_options = true
+}, {
+   args = 3,
+   typechecked("name", "string"),
+   typechecked("description", "string"),
+   typechecked("epilog", "string"),
+   typechecked("usage", "string"),
+   typechecked("help", "string"),
+   typechecked("require_command", "boolean"),
+   typechecked("handle_options", "boolean"),
+   typechecked("action", "function"),
+   typechecked("command_target", "string"),
+   typechecked("help_vertical_space", "number"),
+   typechecked("usage_margin", "number"),
+   typechecked("usage_max_width", "number"),
+   typechecked("help_usage_margin", "number"),
+   typechecked("help_description_margin", "number"),
+   typechecked("help_max_width", "number"),
+   add_help
+})
+
+local Command = class({
+   _aliases = {},
+   _public_aliases = {}
+}, {
+   args = 3,
+   multiname,
+   typechecked("description", "string"),
+   typechecked("epilog", "string"),
+   multiname_hidden,
+   typechecked("summary", "string"),
+   typechecked("target", "string"),
+   typechecked("usage", "string"),
+   typechecked("help", "string"),
+   typechecked("require_command", "boolean"),
+   typechecked("handle_options", "boolean"),
+   typechecked("action", "function"),
+   typechecked("command_target", "string"),
+   typechecked("help_vertical_space", "number"),
+   typechecked("usage_margin", "number"),
+   typechecked("usage_max_width", "number"),
+   typechecked("help_usage_margin", "number"),
+   typechecked("help_description_margin", "number"),
+   typechecked("help_max_width", "number"),
+   typechecked("hidden", "boolean"),
+   add_help
+}, Parser)
+
+local Argument = class({
+   _minargs = 1,
+   _maxargs = 1,
+   _mincount = 1,
+   _maxcount = 1,
+   _defmode = "unused",
+   _show_default = true
+}, {
+   args = 5,
+   typechecked("name", "string"),
+   typechecked("description", "string"),
+   option_default,
+   typechecked("convert", "function", "table"),
+   boundaries("args"),
+   typechecked("target", "string"),
+   typechecked("defmode", "string"),
+   typechecked("show_default", "boolean"),
+   typechecked("argname", "string", "table"),
+   typechecked("choices", "table"),
+   typechecked("hidden", "boolean"),
+   option_action,
+   option_init
+})
+
+local Option = class({
+   _aliases = {},
+   _public_aliases = {},
+   _mincount = 0,
+   _overwrite = true
+}, {
+   args = 6,
+   multiname,
+   typechecked("description", "string"),
+   option_default,
+   typechecked("convert", "function", "table"),
+   boundaries("args"),
+   boundaries("count"),
+   multiname_hidden,
+   typechecked("target", "string"),
+   typechecked("defmode", "string"),
+   typechecked("show_default", "boolean"),
+   typechecked("overwrite", "boolean"),
+   typechecked("argname", "string", "table"),
+   typechecked("choices", "table"),
+   typechecked("hidden", "boolean"),
+   option_action,
+   option_init
+}, Argument)
+
+function Parser:_inherit_property(name, default)
+   local element = self
+
+   while true do
+      local value = element["_" .. name]
+
+      if value ~= nil then
+         return value
+      end
+
+      if not element._parent then
+         return default
+      end
+
+      element = element._parent
+   end
+end
+
+function Argument:_get_argument_list()
+   local buf = {}
+   local i = 1
+
+   while i <= math.min(self._minargs, 3) do
+      local argname = self:_get_argname(i)
+
+      if self._default and self._defmode:find "a" then
+         argname = "[" .. argname .. "]"
+      end
+
+      table.insert(buf, argname)
+      i = i+1
+   end
+
+   while i <= math.min(self._maxargs, 3) do
+      table.insert(buf, "[" .. self:_get_argname(i) .. "]")
+      i = i+1
+
+      if self._maxargs == math.huge then
+         break
+      end
+   end
+
+   if i < self._maxargs then
+      table.insert(buf, "...")
+   end
+
+   return buf
+end
+
+function Argument:_get_usage()
+   local usage = table.concat(self:_get_argument_list(), " ")
+
+   if self._default and self._defmode:find "u" then
+      if self._maxargs > 1 or (self._minargs == 1 and not self._defmode:find "a") then
+         usage = "[" .. usage .. "]"
+      end
+   end
+
+   return usage
+end
+
+function actions.store_true(result, target)
+   result[target] = true
+end
+
+function actions.store_false(result, target)
+   result[target] = false
+end
+
+function actions.store(result, target, argument)
+   result[target] = argument
+end
+
+function actions.count(result, target, _, overwrite)
+   if not overwrite then
+      result[target] = result[target] + 1
+   end
+end
+
+function actions.append(result, target, argument, overwrite)
+   result[target] = result[target] or {}
+   table.insert(result[target], argument)
+
+   if overwrite then
+      table.remove(result[target], 1)
+   end
+end
+
+function actions.concat(result, target, arguments, overwrite)
+   if overwrite then
+      error("'concat' action can't handle too many invocations")
+   end
+
+   result[target] = result[target] or {}
+
+   for _, argument in ipairs(arguments) do
+      table.insert(result[target], argument)
+   end
+end
+
+function Argument:_get_action()
+   local action, init
+
+   if self._maxcount == 1 then
+      if self._maxargs == 0 then
+         action, init = "store_true", nil
+      else
+         action, init = "store", nil
+      end
+   else
+      if self._maxargs == 0 then
+         action, init = "count", 0
+      else
+         action, init = "append", {}
+      end
+   end
+
+   if self._action then
+      action = self._action
+   end
+
+   if self._has_init then
+      init = self._init
+   end
+
+   if type(action) == "string" then
+      action = actions[action]
+   end
+
+   return action, init
+end
+
+-- Returns placeholder for `narg`-th argument.
+function Argument:_get_argname(narg)
+   local argname = self._argname or self:_get_default_argname()
+
+   if type(argname) == "table" then
+      return argname[narg]
+   else
+      return argname
+   end
+end
+
+function Argument:_get_choices_list()
+   return "{" .. table.concat(self._choices, ",") .. "}"
+end
+
+function Argument:_get_default_argname()
+   if self._choices then
+      return self:_get_choices_list()
+   else
+      return "<" .. self._name .. ">"
+   end
+end
+
+function Option:_get_default_argname()
+   if self._choices then
+      return self:_get_choices_list()
+   else
+      return "<" .. self:_get_default_target() .. ">"
+   end
+end
+
+-- Returns labels to be shown in the help message.
+function Argument:_get_label_lines()
+   if self._choices then
+      return {self:_get_choices_list()}
+   else
+      return {self._name}
+   end
+end
+
+function Option:_get_label_lines()
+   local argument_list = self:_get_argument_list()
+
+   if #argument_list == 0 then
+      -- Don't put aliases for simple flags like `-h` on different lines.
+      return {table.concat(self._public_aliases, ", ")}
+   end
+
+   local longest_alias_length = -1
+
+   for _, alias in ipairs(self._public_aliases) do
+      longest_alias_length = math.max(longest_alias_length, #alias)
+   end
+
+   local argument_list_repr = table.concat(argument_list, " ")
+   local lines = {}
+
+   for i, alias in ipairs(self._public_aliases) do
+      local line = (" "):rep(longest_alias_length - #alias) .. alias .. " " .. argument_list_repr
+
+      if i ~= #self._public_aliases then
+         line = line .. ","
+      end
+
+      table.insert(lines, line)
+   end
+
+   return lines
+end
+
+function Command:_get_label_lines()
+   return {table.concat(self._public_aliases, ", ")}
+end
+
+function Argument:_get_description()
+   if self._default and self._show_default then
+      if self._description then
+         return ("%s (default: %s)"):format(self._description, self._default)
+      else
+         return ("default: %s"):format(self._default)
+      end
+   else
+      return self._description or ""
+   end
+end
+
+function Command:_get_description()
+   return self._summary or self._description or ""
+end
+
+function Option:_get_usage()
+   local usage = self:_get_argument_list()
+   table.insert(usage, 1, self._name)
+   usage = table.concat(usage, " ")
+
+   if self._mincount == 0 or self._default then
+      usage = "[" .. usage .. "]"
+   end
+
+   return usage
+end
+
+function Argument:_get_default_target()
+   return self._name
+end
+
+function Option:_get_default_target()
+   local res
+
+   for _, alias in ipairs(self._public_aliases) do
+      if alias:sub(1, 1) == alias:sub(2, 2) then
+         res = alias:sub(3)
+         break
+      end
+   end
+
+   res = res or self._name:sub(2)
+   return (res:gsub("-", "_"))
+end
+
+function Option:_is_vararg()
+   return self._maxargs ~= self._minargs
+end
+
+function Parser:_get_fullname(exclude_root)
+   local parent = self._parent
+   if exclude_root and not parent then
+      return ""
+   end
+   local buf = {self._name}
+
+   while parent do
+      if not exclude_root or parent._parent then
+         table.insert(buf, 1, parent._name)
+      end
+      parent = parent._parent
+   end
+
+   return table.concat(buf, " ")
+end
+
+function Parser:_update_charset(charset)
+   charset = charset or {}
+
+   for _, command in ipairs(self._commands) do
+      command:_update_charset(charset)
+   end
+
+   for _, option in ipairs(self._options) do
+      for _, alias in ipairs(option._aliases) do
+         charset[alias:sub(1, 1)] = true
+      end
+   end
+
+   return charset
+end
+
+function Parser:argument(...)
+   local argument = Argument(...)
+   table.insert(self._arguments, argument)
+   return argument
+end
+
+function Parser:option(...)
+   local option = Option(...)
+   table.insert(self._options, option)
+   return option
+end
+
+function Parser:flag(...)
+   return self:option():args(0)(...)
+end
+
+function Parser:command(...)
+   local command = Command():add_help(true)(...)
+   command._parent = self
+   table.insert(self._commands, command)
+   return command
+end
+
+function Parser:mutex(...)
+   local elements = {...}
+
+   for i, element in ipairs(elements) do
+      local mt = getmetatable(element)
+      assert(mt == Option or mt == Argument, ("bad argument #%d to 'mutex' (Option or Argument expected)"):format(i))
+   end
+
+   table.insert(self._mutexes, elements)
+   return self
+end
+
+function Parser:group(name, ...)
+   assert(type(name) == "string", ("bad argument #1 to 'group' (string expected, got %s)"):format(type(name)))
+
+   local group = {name = name, ...}
+
+   for i, element in ipairs(group) do
+      local mt = getmetatable(element)
+      assert(mt == Option or mt == Argument or mt == Command,
+         ("bad argument #%d to 'group' (Option or Argument or Command expected)"):format(i + 1))
+   end
+
+   table.insert(self._groups, group)
+   return self
+end
+
+local usage_welcome = "Usage: "
+
+function Parser:get_usage()
+   if self._usage then
+      return self._usage
+   end
+
+   local usage_margin = self:_inherit_property("usage_margin", #usage_welcome)
+   local max_usage_width = self:_inherit_property("usage_max_width", 70)
+   local lines = {usage_welcome .. self:_get_fullname()}
+
+   local function add(s)
+      if #lines[#lines]+1+#s <= max_usage_width then
+         lines[#lines] = lines[#lines] .. " " .. s
+      else
+         lines[#lines+1] = (" "):rep(usage_margin) .. s
+      end
+   end
+
+   -- Normally options are before positional arguments in usage messages.
+   -- However, vararg options should be after, because they can't be reliable used
+   -- before a positional argument.
+   -- Mutexes come into play, too, and are shown as soon as possible.
+   -- Overall, output usages in the following order:
+   -- 1. Mutexes that don't have positional arguments or vararg options.
+   -- 2. Options that are not in any mutexes and are not vararg.
+   -- 3. Positional arguments - on their own or as a part of a mutex.
+   -- 4. Remaining mutexes.
+   -- 5. Remaining options.
+
+   local elements_in_mutexes = {}
+   local added_elements = {}
+   local added_mutexes = {}
+   local argument_to_mutexes = {}
+
+   local function add_mutex(mutex, main_argument)
+      if added_mutexes[mutex] then
+         return
+      end
+
+      added_mutexes[mutex] = true
+      local buf = {}
+
+      for _, element in ipairs(mutex) do
+         if not element._hidden and not added_elements[element] then
+            if getmetatable(element) == Option or element == main_argument then
+               table.insert(buf, element:_get_usage())
+               added_elements[element] = true
+            end
+         end
+      end
+
+      if #buf == 1 then
+         add(buf[1])
+      elseif #buf > 1 then
+         add("(" .. table.concat(buf, " | ") .. ")")
+      end
+   end
+
+   local function add_element(element)
+      if not element._hidden and not added_elements[element] then
+         add(element:_get_usage())
+         added_elements[element] = true
+      end
+   end
+
+   for _, mutex in ipairs(self._mutexes) do
+      local is_vararg = false
+      local has_argument = false
+
+      for _, element in ipairs(mutex) do
+         if getmetatable(element) == Option then
+            if element:_is_vararg() then
+               is_vararg = true
+            end
+         else
+            has_argument = true
+            argument_to_mutexes[element] = argument_to_mutexes[element] or {}
+            table.insert(argument_to_mutexes[element], mutex)
+         end
+
+         elements_in_mutexes[element] = true
+      end
+
+      if not is_vararg and not has_argument then
+         add_mutex(mutex)
+      end
+   end
+
+   for _, option in ipairs(self._options) do
+      if not elements_in_mutexes[option] and not option:_is_vararg() then
+         add_element(option)
+      end
+   end
+
+   -- Add usages for positional arguments, together with one mutex containing them, if they are in a mutex.
+   for _, argument in ipairs(self._arguments) do
+      -- Pick a mutex as a part of which to show this argument, take the first one that's still available.
+      local mutex
+
+      if elements_in_mutexes[argument] then
+         for _, argument_mutex in ipairs(argument_to_mutexes[argument]) do
+            if not added_mutexes[argument_mutex] then
+               mutex = argument_mutex
+            end
+         end
+      end
+
+      if mutex then
+         add_mutex(mutex, argument)
+      else
+         add_element(argument)
+      end
+   end
+
+   for _, mutex in ipairs(self._mutexes) do
+      add_mutex(mutex)
+   end
+
+   for _, option in ipairs(self._options) do
+      add_element(option)
+   end
+
+   if #self._commands > 0 then
+      if self._require_command then
+         add("<command>")
+      else
+         add("[<command>]")
+      end
+
+      add("...")
+   end
+
+   return table.concat(lines, "\n")
+end
+
+local function split_lines(s)
+   if s == "" then
+      return {}
+   end
+
+   local lines = {}
+
+   if s:sub(-1) ~= "\n" then
+      s = s .. "\n"
+   end
+
+   for line in s:gmatch("([^\n]*)\n") do
+      table.insert(lines, line)
+   end
+
+   return lines
+end
+
+local function autowrap_line(line, max_length)
+   -- Algorithm for splitting lines is simple and greedy.
+   local result_lines = {}
+
+   -- Preserve original indentation of the line, put this at the beginning of each result line.
+   -- If the first word looks like a list marker ('*', '+', or '-'), add spaces so that starts
+   -- of the second and the following lines vertically align with the start of the second word.
+   local indentation = line:match("^ *")
+
+   if line:find("^ *[%*%+%-]") then
+      indentation = indentation .. " " .. line:match("^ *[%*%+%-]( *)")
+   end
+
+   -- Parts of the last line being assembled.
+   local line_parts = {}
+
+   -- Length of the current line.
+   local line_length = 0
+
+   -- Index of the next character to consider.
+   local index = 1
+
+   while true do
+      local word_start, word_finish, word = line:find("([^ ]+)", index)
+
+      if not word_start then
+         -- Ignore trailing spaces, if any.
+         break
+      end
+
+      local preceding_spaces = line:sub(index, word_start - 1)
+      index = word_finish + 1
+
+      if (#line_parts == 0) or (line_length + #preceding_spaces + #word <= max_length) then
+         -- Either this is the very first word or it fits as an addition to the current line, add it.
+         table.insert(line_parts, preceding_spaces) -- For the very first word this adds the indentation.
+         table.insert(line_parts, word)
+         line_length = line_length + #preceding_spaces + #word
+      else
+         -- Does not fit, finish current line and put the word into a new one.
+         table.insert(result_lines, table.concat(line_parts))
+         line_parts = {indentation, word}
+         line_length = #indentation + #word
+      end
+   end
+
+   if #line_parts > 0 then
+      table.insert(result_lines, table.concat(line_parts))
+   end
+
+   if #result_lines == 0 then
+      -- Preserve empty lines.
+      result_lines[1] = ""
+   end
+
+   return result_lines
+end
+
+-- Automatically wraps lines within given array,
+-- attempting to limit line length to `max_length`.
+-- Existing line splits are preserved.
+local function autowrap(lines, max_length)
+   local result_lines = {}
+
+   for _, line in ipairs(lines) do
+      local autowrapped_lines = autowrap_line(line, max_length)
+
+      for _, autowrapped_line in ipairs(autowrapped_lines) do
+         table.insert(result_lines, autowrapped_line)
+      end
+   end
+
+   return result_lines
+end
+
+function Parser:_get_element_help(element)
+   local label_lines = element:_get_label_lines()
+   local description_lines = split_lines(element:_get_description())
+
+   local result_lines = {}
+
+   -- All label lines should have the same length (except the last one, it has no comma).
+   -- If too long, start description after all the label lines.
+   -- Otherwise, combine label and description lines.
+
+   local usage_margin_len = self:_inherit_property("help_usage_margin", 3)
+   local usage_margin = (" "):rep(usage_margin_len)
+   local description_margin_len = self:_inherit_property("help_description_margin", 25)
+   local description_margin = (" "):rep(description_margin_len)
+
+   local help_max_width = self:_inherit_property("help_max_width")
+
+   if help_max_width then
+      local description_max_width = math.max(help_max_width - description_margin_len, 10)
+      description_lines = autowrap(description_lines, description_max_width)
+   end
+
+   if #label_lines[1] >= (description_margin_len - usage_margin_len) then
+      for _, label_line in ipairs(label_lines) do
+         table.insert(result_lines, usage_margin .. label_line)
+      end
+
+      for _, description_line in ipairs(description_lines) do
+         table.insert(result_lines, description_margin .. description_line)
+      end
+   else
+      for i = 1, math.max(#label_lines, #description_lines) do
+         local label_line = label_lines[i]
+         local description_line = description_lines[i]
+
+         local line = ""
+
+         if label_line then
+            line = usage_margin .. label_line
+         end
+
+         if description_line and description_line ~= "" then
+            line = line .. (" "):rep(description_margin_len - #line) .. description_line
+         end
+
+         table.insert(result_lines, line)
+      end
+   end
+
+   return table.concat(result_lines, "\n")
+end
+
+local function get_group_types(group)
+   local types = {}
+
+   for _, element in ipairs(group) do
+      types[getmetatable(element)] = true
+   end
+
+   return types
+end
+
+function Parser:_add_group_help(blocks, added_elements, label, elements)
+   local buf = {label}
+
+   for _, element in ipairs(elements) do
+      if not element._hidden and not added_elements[element] then
+         added_elements[element] = true
+         table.insert(buf, self:_get_element_help(element))
+      end
+   end
+
+   if #buf > 1 then
+      table.insert(blocks, table.concat(buf, ("\n"):rep(self:_inherit_property("help_vertical_space", 0) + 1)))
+   end
+end
+
+function Parser:get_help()
+   if self._help then
+      return self._help
+   end
+
+   local blocks = {self:get_usage()}
+
+   local help_max_width = self:_inherit_property("help_max_width")
+
+   if self._description then
+      local description = self._description
+
+      if help_max_width then
+         description = table.concat(autowrap(split_lines(description), help_max_width), "\n")
+      end
+
+      table.insert(blocks, description)
+   end
+
+   -- 1. Put groups containing arguments first, then other arguments.
+   -- 2. Put remaining groups containing options, then other options.
+   -- 3. Put remaining groups containing commands, then other commands.
+   -- Assume that an element can't be in several groups.
+   local groups_by_type = {
+      [Argument] = {},
+      [Option] = {},
+      [Command] = {}
+   }
+
+   for _, group in ipairs(self._groups) do
+      local group_types = get_group_types(group)
+
+      for _, mt in ipairs({Argument, Option, Command}) do
+         if group_types[mt] then
+            table.insert(groups_by_type[mt], group)
+            break
+         end
+      end
+   end
+
+   local default_groups = {
+      {name = "Arguments", type = Argument, elements = self._arguments},
+      {name = "Options", type = Option, elements = self._options},
+      {name = "Commands", type = Command, elements = self._commands}
+   }
+
+   local added_elements = {}
+
+   for _, default_group in ipairs(default_groups) do
+      local type_groups = groups_by_type[default_group.type]
+
+      for _, group in ipairs(type_groups) do
+         self:_add_group_help(blocks, added_elements, group.name .. ":", group)
+      end
+
+      local default_label = default_group.name .. ":"
+
+      if #type_groups > 0 then
+         default_label = "Other " .. default_label:gsub("^.", string.lower)
+      end
+
+      self:_add_group_help(blocks, added_elements, default_label, default_group.elements)
+   end
+
+   if self._epilog then
+      local epilog = self._epilog
+
+      if help_max_width then
+         epilog = table.concat(autowrap(split_lines(epilog), help_max_width), "\n")
+      end
+
+      table.insert(blocks, epilog)
+   end
+
+   return table.concat(blocks, "\n\n")
+end
+
+function Parser:add_help_command(value)
+   if value then
+      assert(type(value) == "string" or type(value) == "table",
+         ("bad argument #1 to 'add_help_command' (string or table expected, got %s)"):format(type(value)))
+   end
+
+   local help = self:command()
+      :description "Show help for commands."
+   help:argument "command"
+      :description "The command to show help for."
+      :args "?"
+      :action(function(_, _, cmd)
+         if not cmd then
+            print(self:get_help())
+            os.exit(0)
+         else
+            for _, command in ipairs(self._commands) do
+               for _, alias in ipairs(command._aliases) do
+                  if alias == cmd then
+                     print(command:get_help())
+                     os.exit(0)
+                  end
+               end
+            end
+         end
+         help:error(("unknown command '%s'"):format(cmd))
+      end)
+
+   if value then
+      help = help(value)
+   end
+
+   if not help._name then
+      help "help"
+   end
+
+   help._is_help_command = true
+   return self
+end
+
+function Parser:_is_shell_safe()
+   if self._basename then
+      if self._basename:find("[^%w_%-%+%.]") then
+         return false
+      end
+   else
+      for _, alias in ipairs(self._aliases) do
+         if alias:find("[^%w_%-%+%.]") then
+            return false
+         end
+      end
+   end
+   for _, option in ipairs(self._options) do
+      for _, alias in ipairs(option._aliases) do
+         if alias:find("[^%w_%-%+%.]") then
+            return false
+         end
+      end
+      if option._choices then
+         for _, choice in ipairs(option._choices) do
+            if choice:find("[%s'\"]") then
+               return false
+            end
+         end
+      end
+   end
+   for _, argument in ipairs(self._arguments) do
+      if argument._choices then
+         for _, choice in ipairs(argument._choices) do
+            if choice:find("[%s'\"]") then
+               return false
+            end
+         end
+      end
+   end
+   for _, command in ipairs(self._commands) do
+      if not command:_is_shell_safe() then
+         return false
+      end
+   end
+   return true
+end
+
+function Parser:add_complete(value)
+   if value then
+      assert(type(value) == "string" or type(value) == "table",
+         ("bad argument #1 to 'add_complete' (string or table expected, got %s)"):format(type(value)))
+   end
+
+   local complete = self:option()
+      :description "Output a shell completion script for the specified shell."
+      :args(1)
+      :choices {"bash", "zsh", "fish"}
+      :action(function(_, _, shell)
+         io.write(self["get_" .. shell .. "_complete"](self))
+         os.exit(0)
+      end)
+
+   if value then
+      complete = complete(value)
+   end
+
+   if not complete._name then
+      complete "--completion"
+   end
+
+   return self
+end
+
+function Parser:add_complete_command(value)
+   if value then
+      assert(type(value) == "string" or type(value) == "table",
+         ("bad argument #1 to 'add_complete_command' (string or table expected, got %s)"):format(type(value)))
+   end
+
+   local complete = self:command()
+      :description "Output a shell completion script."
+   complete:argument "shell"
+      :description "The shell to output a completion script for."
+      :choices {"bash", "zsh", "fish"}
+      :action(function(_, _, shell)
+         io.write(self["get_" .. shell .. "_complete"](self))
+         os.exit(0)
+      end)
+
+   if value then
+      complete = complete(value)
+   end
+
+   if not complete._name then
+      complete "completion"
+   end
+
+   return self
+end
+
+local function base_name(pathname)
+   return pathname:gsub("[/\\]*$", ""):match(".*[/\\]([^/\\]*)") or pathname
+end
+
+local function get_short_description(element)
+   local short = element:_get_description():match("^(.-)%.%s")
+   return short or element:_get_description():match("^(.-)%.?$")
+end
+
+function Parser:_get_options()
+   local options = {}
+   for _, option in ipairs(self._options) do
+      for _, alias in ipairs(option._aliases) do
+         table.insert(options, alias)
+      end
+   end
+   return table.concat(options, " ")
+end
+
+function Parser:_get_commands()
+   local commands = {}
+   for _, command in ipairs(self._commands) do
+      for _, alias in ipairs(command._aliases) do
+         table.insert(commands, alias)
+      end
+   end
+   return table.concat(commands, " ")
+end
+
+function Parser:_bash_option_args(buf, indent)
+   local opts = {}
+   for _, option in ipairs(self._options) do
+      if option._choices or option._minargs > 0 then
+         local compreply
+         if option._choices then
+            compreply = 'COMPREPLY=($(compgen -W "' .. table.concat(option._choices, " ") .. '" -- "$cur"))'
+         else
+            compreply = 'COMPREPLY=($(compgen -f -- "$cur"))'
+         end
+         table.insert(opts, (" "):rep(indent + 4) .. table.concat(option._aliases, "|") .. ")")
+         table.insert(opts, (" "):rep(indent + 8) .. compreply)
+         table.insert(opts, (" "):rep(indent + 8) .. "return 0")
+         table.insert(opts, (" "):rep(indent + 8) .. ";;")
+      end
+   end
+
+   if #opts > 0 then
+      table.insert(buf, (" "):rep(indent) .. 'case "$prev" in')
+      table.insert(buf, table.concat(opts, "\n"))
+      table.insert(buf, (" "):rep(indent) .. "esac\n")
+   end
+end
+
+function Parser:_bash_get_cmd(buf, indent)
+   if #self._commands == 0 then
+      return
+   end
+
+   table.insert(buf, (" "):rep(indent) .. 'args=("${args[@]:1}")')
+   table.insert(buf, (" "):rep(indent) .. 'for arg in "${args[@]}"; do')
+   table.insert(buf, (" "):rep(indent + 4) .. 'case "$arg" in')
+
+   for _, command in ipairs(self._commands) do
+      table.insert(buf, (" "):rep(indent + 8) .. table.concat(command._aliases, "|") .. ")")
+      if self._parent then
+         table.insert(buf, (" "):rep(indent + 12) .. 'cmd="$cmd ' .. command._name .. '"')
+      else
+         table.insert(buf, (" "):rep(indent + 12) .. 'cmd="' .. command._name .. '"')
+      end
+      table.insert(buf, (" "):rep(indent + 12) .. 'opts="$opts ' .. command:_get_options() .. '"')
+      command:_bash_get_cmd(buf, indent + 12)
+      table.insert(buf, (" "):rep(indent + 12) .. "break")
+      table.insert(buf, (" "):rep(indent + 12) .. ";;")
+   end
+
+   table.insert(buf, (" "):rep(indent + 4) .. "esac")
+   table.insert(buf, (" "):rep(indent) .. "done")
+end
+
+function Parser:_bash_cmd_completions(buf)
+   local cmd_buf = {}
+   if self._parent then
+      self:_bash_option_args(cmd_buf, 12)
+   end
+   if #self._commands > 0 then
+      table.insert(cmd_buf, (" "):rep(12) .. 'COMPREPLY=($(compgen -W "' .. self:_get_commands() .. '" -- "$cur"))')
+   elseif self._is_help_command then
+      table.insert(cmd_buf, (" "):rep(12)
+         .. 'COMPREPLY=($(compgen -W "'
+         .. self._parent:_get_commands()
+         .. '" -- "$cur"))')
+   end
+   if #cmd_buf > 0 then
+      table.insert(buf, (" "):rep(8) .. "'" .. self:_get_fullname(true) .. "')")
+      table.insert(buf, table.concat(cmd_buf, "\n"))
+      table.insert(buf, (" "):rep(12) .. ";;")
+   end
+
+   for _, command in ipairs(self._commands) do
+      command:_bash_cmd_completions(buf)
+   end
+end
+
+function Parser:get_bash_complete()
+   self._basename = base_name(self._name)
+   assert(self:_is_shell_safe())
+   local buf = {([[
+_%s() {
+    local IFS=$' \t\n'
+    local args cur prev cmd opts arg
+    args=("${COMP_WORDS[@]}")
+    cur="${COMP_WORDS[COMP_CWORD]}"
+    prev="${COMP_WORDS[COMP_CWORD-1]}"
+    opts="%s"
+]]):format(self._basename, self:_get_options())}
+
+   self:_bash_option_args(buf, 4)
+   self:_bash_get_cmd(buf, 4)
+   if #self._commands > 0 then
+      table.insert(buf, "")
+      table.insert(buf, (" "):rep(4) .. 'case "$cmd" in')
+      self:_bash_cmd_completions(buf)
+      table.insert(buf, (" "):rep(4) .. "esac\n")
+   end
+
+   table.insert(buf, ([=[
+    if [[ "$cur" = -* ]]; then
+        COMPREPLY=($(compgen -W "$opts" -- "$cur"))
+    fi
+}
+
+complete -F _%s -o bashdefault -o default %s
+]=]):format(self._basename, self._basename))
+
+   return table.concat(buf, "\n")
+end
+
+function Parser:_zsh_arguments(buf, cmd_name, indent)
+   if self._parent then
+      table.insert(buf, (" "):rep(indent) .. "options=(")
+      table.insert(buf, (" "):rep(indent + 2) .. "$options")
+   else
+      table.insert(buf, (" "):rep(indent) .. "local -a options=(")
+   end
+
+   for _, option in ipairs(self._options) do
+      local line = {}
+      if #option._aliases > 1 then
+         if option._maxcount > 1 then
+            table.insert(line, '"*"')
+         end
+         table.insert(line, "{" .. table.concat(option._aliases, ",") .. '}"')
+      else
+         table.insert(line, '"')
+         if option._maxcount > 1 then
+            table.insert(line, "*")
+         end
+         table.insert(line, option._name)
+      end
+      if option._description then
+         local description = get_short_description(option):gsub('["%]:`$]', "\\%0")
+         table.insert(line, "[" .. description .. "]")
+      end
+      if option._maxargs == math.huge then
+         table.insert(line, ":*")
+      end
+      if option._choices then
+         table.insert(line, ": :(" .. table.concat(option._choices, " ") .. ")")
+      elseif option._maxargs > 0 then
+         table.insert(line, ": :_files")
+      end
+      table.insert(line, '"')
+      table.insert(buf, (" "):rep(indent + 2) .. table.concat(line))
+   end
+
+   table.insert(buf, (" "):rep(indent) .. ")")
+   table.insert(buf, (" "):rep(indent) .. "_arguments -s -S \\")
+   table.insert(buf, (" "):rep(indent + 2) .. "$options \\")
+
+   if self._is_help_command then
+      table.insert(buf, (" "):rep(indent + 2) .. '": :(' .. self._parent:_get_commands() .. ')" \\')
+   else
+      for _, argument in ipairs(self._arguments) do
+         local spec
+         if argument._choices then
+            spec = ": :(" .. table.concat(argument._choices, " ") .. ")"
+         else
+            spec = ": :_files"
+         end
+         if argument._maxargs == math.huge then
+            table.insert(buf, (" "):rep(indent + 2) .. '"*' .. spec .. '" \\')
+            break
+         end
+         for _ = 1, argument._maxargs do
+            table.insert(buf, (" "):rep(indent + 2) .. '"' .. spec .. '" \\')
+         end
+      end
+
+      if #self._commands > 0 then
+         table.insert(buf, (" "):rep(indent + 2) .. '": :_' .. cmd_name .. '_cmds" \\')
+         table.insert(buf, (" "):rep(indent + 2) .. '"*:: :->args" \\')
+      end
+   end
+
+   table.insert(buf, (" "):rep(indent + 2) .. "&& return 0")
+end
+
+function Parser:_zsh_cmds(buf, cmd_name)
+   table.insert(buf, "\n_" .. cmd_name .. "_cmds() {")
+   table.insert(buf, "  local -a commands=(")
+
+   for _, command in ipairs(self._commands) do
+      local line = {}
+      if #command._aliases > 1 then
+         table.insert(line, "{" .. table.concat(command._aliases, ",") .. '}"')
+      else
+         table.insert(line, '"' .. command._name)
+      end
+      if command._description then
+         table.insert(line, ":" .. get_short_description(command):gsub('["`$]', "\\%0"))
+      end
+      table.insert(buf, "    " .. table.concat(line) .. '"')
+   end
+
+   table.insert(buf, '  )\n  _describe "command" commands\n}')
+end
+
+function Parser:_zsh_complete_help(buf, cmds_buf, cmd_name, indent)
+   if #self._commands == 0 then
+      return
+   end
+
+   self:_zsh_cmds(cmds_buf, cmd_name)
+   table.insert(buf, "\n" .. (" "):rep(indent) .. "case $words[1] in")
+
+   for _, command in ipairs(self._commands) do
+      local name = cmd_name .. "_" .. command._name
+      table.insert(buf, (" "):rep(indent + 2) .. table.concat(command._aliases, "|") .. ")")
+      command:_zsh_arguments(buf, name, indent + 4)
+      command:_zsh_complete_help(buf, cmds_buf, name, indent + 4)
+      table.insert(buf, (" "):rep(indent + 4) .. ";;\n")
+   end
+
+   table.insert(buf, (" "):rep(indent) .. "esac")
+end
+
+function Parser:get_zsh_complete()
+   self._basename = base_name(self._name)
+   assert(self:_is_shell_safe())
+   local buf = {("#compdef %s\n"):format(self._basename)}
+   local cmds_buf = {}
+   table.insert(buf, "_" .. self._basename .. "() {")
+   if #self._commands > 0 then
+      table.insert(buf, "  local context state state_descr line")
+      table.insert(buf, "  typeset -A opt_args\n")
+   end
+   self:_zsh_arguments(buf, self._basename, 2)
+   self:_zsh_complete_help(buf, cmds_buf, self._basename, 2)
+   table.insert(buf, "\n  return 1")
+   table.insert(buf, "}")
+
+   local result = table.concat(buf, "\n")
+   if #cmds_buf > 0 then
+      result = result .. "\n" .. table.concat(cmds_buf, "\n")
+   end
+   return result .. "\n\n_" .. self._basename .. "\n"
+end
+
+local function fish_escape(string)
+   return string:gsub("[\\']", "\\%0")
+end
+
+function Parser:_fish_get_cmd(buf, indent)
+   if #self._commands == 0 then
+      return
+   end
+
+   table.insert(buf, (" "):rep(indent) .. "set -e cmdline[1]")
+   table.insert(buf, (" "):rep(indent) .. "for arg in $cmdline")
+   table.insert(buf, (" "):rep(indent + 4) .. "switch $arg")
+
+   for _, command in ipairs(self._commands) do
+      table.insert(buf, (" "):rep(indent + 8) .. "case " .. table.concat(command._aliases, " "))
+      table.insert(buf, (" "):rep(indent + 12) .. "set cmd $cmd " .. command._name)
+      command:_fish_get_cmd(buf, indent + 12)
+      table.insert(buf, (" "):rep(indent + 12) .. "break")
+   end
+
+   table.insert(buf, (" "):rep(indent + 4) .. "end")
+   table.insert(buf, (" "):rep(indent) .. "end")
+end
+
+function Parser:_fish_complete_help(buf, basename)
+   local prefix = "complete -c " .. basename
+   table.insert(buf, "")
+
+   for _, command in ipairs(self._commands) do
+      local aliases = table.concat(command._aliases, " ")
+      local line
+      if self._parent then
+         line = ("%s -n '__fish_%s_using_command %s' -xa '%s'")
+            :format(prefix, basename, self:_get_fullname(true), aliases)
+      else
+         line = ("%s -n '__fish_%s_using_command' -xa '%s'"):format(prefix, basename, aliases)
+      end
+      if command._description then
+         line = ("%s -d '%s'"):format(line, fish_escape(get_short_description(command)))
+      end
+      table.insert(buf, line)
+   end
+
+   if self._is_help_command then
+      local line = ("%s -n '__fish_%s_using_command %s' -xa '%s'")
+         :format(prefix, basename, self:_get_fullname(true), self._parent:_get_commands())
+      table.insert(buf, line)
+   end
+
+   for _, option in ipairs(self._options) do
+      local parts = {prefix}
+
+      if self._parent then
+         table.insert(parts, "-n '__fish_" .. basename .. "_seen_command " .. self:_get_fullname(true) .. "'")
+      end
+
+      for _, alias in ipairs(option._aliases) do
+         if alias:match("^%-.$") then
+            table.insert(parts, "-s " .. alias:sub(2))
+         elseif alias:match("^%-%-.+") then
+            table.insert(parts, "-l " .. alias:sub(3))
+         end
+      end
+
+      if option._choices then
+         table.insert(parts, "-xa '" .. table.concat(option._choices, " ") .. "'")
+      elseif option._minargs > 0 then
+         table.insert(parts, "-r")
+      end
+
+      if option._description then
+         table.insert(parts, "-d '" .. fish_escape(get_short_description(option)) .. "'")
+      end
+
+      table.insert(buf, table.concat(parts, " "))
+   end
+
+   for _, command in ipairs(self._commands) do
+      command:_fish_complete_help(buf, basename)
+   end
+end
+
+function Parser:get_fish_complete()
+   self._basename = base_name(self._name)
+   assert(self:_is_shell_safe())
+   local buf = {}
+
+   if #self._commands > 0 then
+      table.insert(buf, ([[
+function __fish_%s_print_command
+    set -l cmdline (commandline -poc)
+    set -l cmd]]):format(self._basename))
+      self:_fish_get_cmd(buf, 4)
+      table.insert(buf, ([[
+    echo "$cmd"
+end
+
+function __fish_%s_using_command
+    test (__fish_%s_print_command) = "$argv"
+    and return 0
+    or return 1
+end
+
+function __fish_%s_seen_command
+    string match -q "$argv*" (__fish_%s_print_command)
+    and return 0
+    or return 1
+end]]):format(self._basename, self._basename, self._basename, self._basename))
+   end
+
+   self:_fish_complete_help(buf, self._basename)
+   return table.concat(buf, "\n") .. "\n"
+end
+
+local function get_tip(context, wrong_name)
+   local context_pool = {}
+   local possible_name
+   local possible_names = {}
+
+   for name in pairs(context) do
+      if type(name) == "string" then
+         for i = 1, #name do
+            possible_name = name:sub(1, i - 1) .. name:sub(i + 1)
+
+            if not context_pool[possible_name] then
+               context_pool[possible_name] = {}
+            end
+
+            table.insert(context_pool[possible_name], name)
+         end
+      end
+   end
+
+   for i = 1, #wrong_name + 1 do
+      possible_name = wrong_name:sub(1, i - 1) .. wrong_name:sub(i + 1)
+
+      if context[possible_name] then
+         possible_names[possible_name] = true
+      elseif context_pool[possible_name] then
+         for _, name in ipairs(context_pool[possible_name]) do
+            possible_names[name] = true
+         end
+      end
+   end
+
+   local first = next(possible_names)
+
+   if first then
+      if next(possible_names, first) then
+         local possible_names_arr = {}
+
+         for name in pairs(possible_names) do
+            table.insert(possible_names_arr, "'" .. name .. "'")
+         end
+
+         table.sort(possible_names_arr)
+         return "\nDid you mean one of these: " .. table.concat(possible_names_arr, " ") .. "?"
+      else
+         return "\nDid you mean '" .. first .. "'?"
+      end
+   else
+      return ""
+   end
+end
+
+local ElementState = class({
+   invocations = 0
+})
+
+function ElementState:__call(state, element)
+   self.state = state
+   self.result = state.result
+   self.element = element
+   self.target = element._target or element:_get_default_target()
+   self.action, self.result[self.target] = element:_get_action()
+   return self
+end
+
+function ElementState:error(fmt, ...)
+   self.state:error(fmt, ...)
+end
+
+function ElementState:convert(argument, index)
+   local converter = self.element._convert
+
+   if converter then
+      local ok, err
+
+      if type(converter) == "function" then
+         ok, err = converter(argument)
+      elseif type(converter[index]) == "function" then
+         ok, err = converter[index](argument)
+      else
+         ok = converter[argument]
+      end
+
+      if ok == nil then
+         self:error(err and "%s" or "malformed argument '%s'", err or argument)
+      end
+
+      argument = ok
+   end
+
+   return argument
+end
+
+function ElementState:default(mode)
+   return self.element._defmode:find(mode) and self.element._default
+end
+
+local function bound(noun, min, max, is_max)
+   local res = ""
+
+   if min ~= max then
+      res = "at " .. (is_max and "most" or "least") .. " "
+   end
+
+   local number = is_max and max or min
+   return res .. tostring(number) .. " " .. noun ..  (number == 1 and "" or "s")
+end
+
+function ElementState:set_name(alias)
+   self.name = ("%s '%s'"):format(alias and "option" or "argument", alias or self.element._name)
+end
+
+function ElementState:invoke()
+   self.open = true
+   self.overwrite = false
+
+   if self.invocations >= self.element._maxcount then
+      if self.element._overwrite then
+         self.overwrite = true
+      else
+         local num_times_repr = bound("time", self.element._mincount, self.element._maxcount, true)
+         self:error("%s must be used %s", self.name, num_times_repr)
+      end
+   else
+      self.invocations = self.invocations + 1
+   end
+
+   self.args = {}
+
+   if self.element._maxargs <= 0 then
+      self:close()
+   end
+
+   return self.open
+end
+
+function ElementState:check_choices(argument)
+   if self.element._choices then
+      for _, choice in ipairs(self.element._choices) do
+         if argument == choice then
+            return
+         end
+      end
+      local choices_list = "'" .. table.concat(self.element._choices, "', '") .. "'"
+      local is_option = getmetatable(self.element) == Option
+      self:error("%s%s must be one of %s", is_option and "argument for " or "", self.name, choices_list)
+   end
+end
+
+function ElementState:pass(argument)
+   self:check_choices(argument)
+   argument = self:convert(argument, #self.args + 1)
+   table.insert(self.args, argument)
+
+   if #self.args >= self.element._maxargs then
+      self:close()
+   end
+
+   return self.open
+end
+
+function ElementState:complete_invocation()
+   while #self.args < self.element._minargs do
+      self:pass(self.element._default)
+   end
+end
+
+function ElementState:close()
+   if self.open then
+      self.open = false
+
+      if #self.args < self.element._minargs then
+         if self:default("a") then
+            self:complete_invocation()
+         else
+            if #self.args == 0 then
+               if getmetatable(self.element) == Argument then
+                  self:error("missing %s", self.name)
+               elseif self.element._maxargs == 1 then
+                  self:error("%s requires an argument", self.name)
+               end
+            end
+
+            self:error("%s requires %s", self.name, bound("argument", self.element._minargs, self.element._maxargs))
+         end
+      end
+
+      local args
+
+      if self.element._maxargs == 0 then
+         args = self.args[1]
+      elseif self.element._maxargs == 1 then
+         if self.element._minargs == 0 and self.element._mincount ~= self.element._maxcount then
+            args = self.args
+         else
+            args = self.args[1]
+         end
+      else
+         args = self.args
+      end
+
+      self.action(self.result, self.target, args, self.overwrite)
+   end
+end
+
+local ParseState = class({
+   result = {},
+   options = {},
+   arguments = {},
+   argument_i = 1,
+   element_to_mutexes = {},
+   mutex_to_element_state = {},
+   command_actions = {}
+})
+
+function ParseState:__call(parser, error_handler)
+   self.parser = parser
+   self.error_handler = error_handler
+   self.charset = parser:_update_charset()
+   self:switch(parser)
+   return self
+end
+
+function ParseState:error(fmt, ...)
+   self.error_handler(self.parser, fmt:format(...))
+end
+
+function ParseState:switch(parser)
+   self.parser = parser
+
+   if parser._action then
+      table.insert(self.command_actions, {action = parser._action, name = parser._name})
+   end
+
+   for _, option in ipairs(parser._options) do
+      option = ElementState(self, option)
+      table.insert(self.options, option)
+
+      for _, alias in ipairs(option.element._aliases) do
+         self.options[alias] = option
+      end
+   end
+
+   for _, mutex in ipairs(parser._mutexes) do
+      for _, element in ipairs(mutex) do
+         if not self.element_to_mutexes[element] then
+            self.element_to_mutexes[element] = {}
+         end
+
+         table.insert(self.element_to_mutexes[element], mutex)
+      end
+   end
+
+   for _, argument in ipairs(parser._arguments) do
+      argument = ElementState(self, argument)
+      table.insert(self.arguments, argument)
+      argument:set_name()
+      argument:invoke()
+   end
+
+   self.handle_options = parser._handle_options
+   self.argument = self.arguments[self.argument_i]
+   self.commands = parser._commands
+
+   for _, command in ipairs(self.commands) do
+      for _, alias in ipairs(command._aliases) do
+         self.commands[alias] = command
+      end
+   end
+end
+
+function ParseState:get_option(name)
+   local option = self.options[name]
+
+   if not option then
+      self:error("unknown option '%s'%s", name, get_tip(self.options, name))
+   else
+      return option
+   end
+end
+
+function ParseState:get_command(name)
+   local command = self.commands[name]
+
+   if not command then
+      if #self.commands > 0 then
+         self:error("unknown command '%s'%s", name, get_tip(self.commands, name))
+      else
+         self:error("too many arguments")
+      end
+   else
+      return command
+   end
+end
+
+function ParseState:check_mutexes(element_state)
+   if self.element_to_mutexes[element_state.element] then
+      for _, mutex in ipairs(self.element_to_mutexes[element_state.element]) do
+         local used_element_state = self.mutex_to_element_state[mutex]
+
+         if used_element_state and used_element_state ~= element_state then
+            self:error("%s can not be used together with %s", element_state.name, used_element_state.name)
+         else
+            self.mutex_to_element_state[mutex] = element_state
+         end
+      end
+   end
+end
+
+function ParseState:invoke(option, name)
+   self:close()
+   option:set_name(name)
+   self:check_mutexes(option, name)
+
+   if option:invoke() then
+      self.option = option
+   end
+end
+
+function ParseState:pass(arg)
+   if self.option then
+      if not self.option:pass(arg) then
+         self.option = nil
+      end
+   elseif self.argument then
+      self:check_mutexes(self.argument)
+
+      if not self.argument:pass(arg) then
+         self.argument_i = self.argument_i + 1
+         self.argument = self.arguments[self.argument_i]
+      end
+   else
+      local command = self:get_command(arg)
+      self.result[command._target or command._name] = true
+
+      if self.parser._command_target then
+         self.result[self.parser._command_target] = command._name
+      end
+
+      self:switch(command)
+   end
+end
+
+function ParseState:close()
+   if self.option then
+      self.option:close()
+      self.option = nil
+   end
+end
+
+function ParseState:finalize()
+   self:close()
+
+   for i = self.argument_i, #self.arguments do
+      local argument = self.arguments[i]
+      if #argument.args == 0 and argument:default("u") then
+         argument:complete_invocation()
+      else
+         argument:close()
+      end
+   end
+
+   if self.parser._require_command and #self.commands > 0 then
+      self:error("a command is required")
+   end
+
+   for _, option in ipairs(self.options) do
+      option.name = option.name or ("option '%s'"):format(option.element._name)
+
+      if option.invocations == 0 then
+         if option:default("u") then
+            option:invoke()
+            option:complete_invocation()
+            option:close()
+         end
+      end
+
+      local mincount = option.element._mincount
+
+      if option.invocations < mincount then
+         if option:default("a") then
+            while option.invocations < mincount do
+               option:invoke()
+               option:close()
+            end
+         elseif option.invocations == 0 then
+            self:error("missing %s", option.name)
+         else
+            self:error("%s must be used %s", option.name, bound("time", mincount, option.element._maxcount))
+         end
+      end
+   end
+
+   for i = #self.command_actions, 1, -1 do
+      self.command_actions[i].action(self.result, self.command_actions[i].name)
+   end
+end
+
+function ParseState:parse(args)
+   for _, arg in ipairs(args) do
+      local plain = true
+
+      if self.handle_options then
+         local first = arg:sub(1, 1)
+
+         if self.charset[first] then
+            if #arg > 1 then
+               plain = false
+
+               if arg:sub(2, 2) == first then
+                  if #arg == 2 then
+                     if self.options[arg] then
+                        local option = self:get_option(arg)
+                        self:invoke(option, arg)
+                     else
+                        self:close()
+                     end
+
+                     self.handle_options = false
+                  else
+                     local equals = arg:find "="
+                     if equals then
+                        local name = arg:sub(1, equals - 1)
+                        local option = self:get_option(name)
+
+                        if option.element._maxargs <= 0 then
+                           self:error("option '%s' does not take arguments", name)
+                        end
+
+                        self:invoke(option, name)
+                        self:pass(arg:sub(equals + 1))
+                     else
+                        local option = self:get_option(arg)
+                        self:invoke(option, arg)
+                     end
+                  end
+               else
+                  for i = 2, #arg do
+                     local name = first .. arg:sub(i, i)
+                     local option = self:get_option(name)
+                     self:invoke(option, name)
+
+                     if i ~= #arg and option.element._maxargs > 0 then
+                        self:pass(arg:sub(i + 1))
+                        break
+                     end
+                  end
+               end
+            end
+         end
+      end
+
+      if plain then
+         self:pass(arg)
+      end
+   end
+
+   self:finalize()
+   return self.result
+end
+
+function Parser:error(msg)
+   io.stderr:write(("%s\n\nError: %s\n"):format(self:get_usage(), msg))
+   os.exit(1)
+end
+
+-- Compatibility with strict.lua and other checkers:
+local default_cmdline = rawget(_G, "arg") or {}
+
+function Parser:_parse(args, error_handler)
+   return ParseState(self, error_handler):parse(args or default_cmdline)
+end
+
+function Parser:parse(args)
+   return self:_parse(args, self.error)
+end
+
+local function xpcall_error_handler(err)
+   if not debug then
+      return tostring(err)
+   end
+   return tostring(err) .. "\noriginal " .. debug.traceback("", 2):sub(2)
+end
+
+function Parser:pparse(args)
+   local parse_error
+
+   local ok, result = xpcall(function()
+      return self:_parse(args, function(_, err)
+         parse_error = err
+         error(err, 0)
+      end)
+   end, xpcall_error_handler)
+
+   if ok then
+      return true, result
+   elseif not parse_error then
+      error(result, 0)
+   else
+      return false, parse_error
+   end
+end
+
+local argparse = {}
+
+argparse.version = "0.7.0"
+
+setmetatable(argparse, {__call = function(_, ...)
+   return Parser(default_cmdline[0]):add_help(true)(...)
+end})
+
+return argparse