Allow using multiple constructor arguments for configuring elements

Disable undocumented ability to specify aliases as arguments
for constructors, e.g. parser:option("-f", "--foo"), and instead
order properties and pass constructor arguments to them.
E.g. parser:argument("foo", "A foo that bars") sets argument
name to foo and description to "A foo that bars".

TODO: remove "aliases" property, instead allow setting several
names in one string by separating them using space.
TODO: reorder properties so that most useful ones could be used
as constructor arguments.

spec/arguments_spec.lua

@@ -34,30 +34,30 @@ describe("tests related to positional arguments", function()
 
       it("handles multi-argument correctly", function()
          local parser = Parser()
-         parser:argument("foo", {
+         parser:argument "foo" {
             args = "*"
-         })
+         }
          local args = parser:parse({"bar", "baz", "qu"})
          assert.same({foo = {"bar", "baz", "qu"}}, args)
       end)
 
       it("handles restrained multi-argument correctly", function()
          local parser = Parser()
-         parser:argument("foo", {
+         parser:argument "foo" {
             args = "2-4"
-         })
+         }
          local args = parser:parse({"bar", "baz"})
          assert.same({foo = {"bar", "baz"}}, args)
       end)
 
       it("handles several multi-arguments correctly", function()
          local parser = Parser()
-         parser:argument("foo1", {
+         parser:argument "foo1" {
             args = "1-2"
-         })
+         }
-         parser:argument("foo2", {
+         parser:argument "foo2" {
             args = "*"
-         })
+         }
          local args = parser:parse({"bar"})
          assert.same({foo1 = {"bar"}, foo2 = {}}, args)
          args = parser:parse({"bar", "baz", "qu"})
@@ -134,31 +134,31 @@ describe("tests related to positional arguments", function()
 
       it("handles too few arguments with multi-argument correctly", function()
          local parser = Parser()
-         parser:argument("foo", {
+         parser:argument "foo" {
             args = "2-4"
-         })
+         }
          assert.has_error(function() parser:parse{"foo"} end, "too few arguments")
       end)
 
       it("handles too many arguments with several multi-arguments correctly", function()
          local parser = Parser()
-         parser:argument("foo1", {
+         parser:argument "foo1" {
             args = "1-2"
-         })
+         }
-         parser:argument("foo2", {
+         parser:argument "foo2" {
             args = "0-1"
-         })
+         }
          assert.has_error(function() parser:parse{"foo", "bar", "baz", "qu"} end, "too many arguments")
       end)
 
       it("handles too few arguments with several multi-arguments correctly", function()
          local parser = Parser()
-         parser:argument("foo1", {
+         parser:argument "foo1" {
             args = "1-2"
-         })
+         }
-         parser:argument("foo2", {
+         parser:argument "foo2" {
             args = "*"
-         })
+         }
          assert.has_error(function() parser:parse{} end, "too few arguments")
       end)
    end)

spec/default_spec.lua

@@ -15,31 +15,31 @@ describe("tests related to default values", function()
 
       it("handles default argument for multi-argument correctly", function()
          local parser = Parser()
-         parser:argument("foo", {
+         parser:argument "foo" {
             args = 3,
             default = "bar",
             defmode = "arg"
-         })
+         }
          local args = parser:parse{"baz"}
          assert.same({foo = {"baz", "bar", "bar"}}, args)
       end)
 
       it("handles default value for multi-argument correctly", function()
          local parser = Parser()
-         parser:argument("foo", {
+         parser:argument "foo" {
             args = 3,
             default = "bar"
-         })
+         }
          local args = parser:parse{}
          assert.same({foo = {"bar", "bar", "bar"}}, args)
       end)
 
       it("does not use default values if not needed", function()
          local parser = Parser()
-         parser:argument("foo", {
+         parser:argument "foo" {
             args = "1-2",
             default = "bar"
-         })
+         }
          local args = parser:parse({"baz"})
          assert.same({foo = {"baz"}}, args)
       end)
@@ -60,20 +60,20 @@ describe("tests related to default values", function()
 
       it("handles option with default value for multi-argument option correctly", function()
          local parser = Parser()
-         parser:option("-s", "--several", {
+         parser:option "-s" "--several" {
             default = "foo",
             args = "2-3"
-         })
+         }
          local args = parser:parse{}
          assert.same({several = {"foo", "foo"}}, args)
       end)
 
       it("handles option with default value and argument", function()
          local parser = Parser()
-         parser:option("-o", "--output", {
+         parser:option "-o" "--output" {
             default = "a.out",
             defmode = "arg+count"
-         })
+         }
          local args = parser:parse{}
          assert.same({output = "a.out"}, args)
          args = parser:parse{"-o"}
@@ -94,43 +94,43 @@ describe("tests related to default values", function()
 
       it("doesn't use default argument if option is not invoked", function()
          local parser = Parser()
-         parser:option("-f", "--foo", {
+         parser:option "-f" "--foo" {
             default = "bar",
             defmode = "arg"
-         })
+         }
          local args = parser:parse{}
          assert.same({}, args)
       end)
 
       it("handles default multi-argument correctly", function()
          local parser = Parser()
-         parser:option("-f", "--foo", {
+         parser:option "-f" "--foo" {
             args = 3,
             default = "bar",
             defmode = "arg"
-         })
+         }
          local args = parser:parse({"--foo=baz"})
          assert.same({foo = {"baz", "bar", "bar"}}, args)
       end)
 
       it("does not use default values if not needed", function()
          local parser = Parser()
-          parser:option("-f", "--foo", {
+          parser:option "-f" "--foo" {
             args = "1-2",
             default = "bar",
             defmode = "arg"
-         })
+         }
          local args = parser:parse({"-f", "baz"})
          assert.same({foo = {"baz"}}, args)
       end)
 
       it("handles multi-count options with default value correctly", function()
          local parser = Parser()
-          parser:option("-f", "--foo", {
+          parser:option "-f" "--foo" {
             count = "*",
             default = "bar",
             defmode = "arg + count"
-         })
+         }
          local args = parser:parse({"-f", "--foo=baz", "--foo"})
          assert.same({foo = {"bar", "baz", "bar"}}, args)
       end)

spec/help_spec.lua

@@ -53,8 +53,7 @@ An epilog. ]], parser:get_help())
          :args "2"
       parser:argument "maybe-fourth"
          :args "?"
-      parser:argument "others"
+      parser:argument("others", "Optional. ")
-         :description "Optional. "
          :args "*"
 
       assert.equal([[

spec/options_spec.lua

@@ -5,21 +5,21 @@ describe("tests related to options", function()
    describe("passing correct options", function()
       it("handles no options passed correctly", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          local args = parser:parse({})
          assert.same({}, args)
       end)
 
       it("handles one option correctly", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          local args = parser:parse({"--server", "foo"})
          assert.same({server = "foo"}, args)
       end)
 
       it("normalizes default target", function()
          local parser = Parser()
-         parser:option("--from-server")
+         parser:option "--from-server"
          local args = parser:parse({"--from-server", "foo"})
          assert.same({from_server = "foo"}, args)
       end)
@@ -34,39 +34,39 @@ describe("tests related to options", function()
 
       it("handles GNU-style long options", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          local args = parser:parse({"--server=foo"})
          assert.same({server = "foo"}, args)
       end)
 
       it("handles GNU-style long options even when it could take more arguments", function()
          local parser = Parser()
-         parser:option("-s", "--server", {
+         parser:option "-s" "--server" {
             args = "*"
-         })
+         }
          local args = parser:parse({"--server=foo"})
          assert.same({server = {"foo"}}, args)
       end)
 
       it("handles GNU-style long options for multi-argument options", function()
          local parser = Parser()
-         parser:option("-s", "--server", {
+         parser:option "-s" "--server" {
             args = "1-2"
-         })
+         }
          local args = parser:parse({"--server=foo", "bar"})
          assert.same({server = {"foo", "bar"}}, args)
       end)
 
       it("handles short option correclty", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          local args = parser:parse({"-s", "foo"})
          assert.same({server = "foo"}, args)
       end)
 
       it("handles flag correclty", function()
          local parser = Parser()
-         parser:flag("-q", "--quiet")
+         parser:flag "-q" "--quiet"
          local args = parser:parse({"--quiet"})
          assert.same({quiet = true}, args)
          args = parser:parse({})
@@ -75,23 +75,23 @@ describe("tests related to options", function()
 
       it("handles combined flags correclty", function()
          local parser = Parser()
-         parser:flag("-q", "--quiet")
+         parser:flag "-q" "--quiet"
-         parser:flag("-f", "--fast")
+         parser:flag "-f" "--fast"
          local args = parser:parse({"-qf"})
          assert.same({quiet = true, fast = true}, args)
       end)
 
       it("handles short options without space between option and argument", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          local args = parser:parse({"-sfoo"})
          assert.same({server = "foo"}, args)
       end)
 
       it("handles flags combined with short option correclty", function()
          local parser = Parser()
-         parser:flag("-q", "--quiet")
+         parser:flag "-q" "--quiet"
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          local args = parser:parse({"-qsfoo"})
          assert.same({quiet = true, server = "foo"}, args)
       end)
@@ -152,27 +152,27 @@ describe("tests related to options", function()
       describe("Options with optional argument", function()
          it("handles emptiness correctly", function()
             local parser = Parser()
-            parser:option("-p", "--password", {
+            parser:option "-p" "--password" {
                args = "?"
-            })
+            }
             local args = parser:parse({})
             assert.same({}, args)
          end)
 
          it("handles option without argument correctly", function()
             local parser = Parser()
-            parser:option("-p", "--password", {
+            parser:option "-p" "--password" {
                args = "?"
-            })
+            }
             local args = parser:parse({"-p"})
             assert.same({password = {}}, args)
          end)
 
          it("handles option with argument correctly", function()
             local parser = Parser()
-            parser:option("-p", "--password", {
+            parser:option "-p" "--password" {
                args = "?"
-            })
+            }
             local args = parser:parse({"-p", "password"})
             assert.same({password = {"password"}}, args)
          end)
@@ -180,9 +180,9 @@ describe("tests related to options", function()
 
       it("handles multi-argument options correctly", function()
          local parser = Parser()
-         parser:option("--pair", {
+         parser:option "--pair" {
             args = 2
-         })
+         }
          local args = parser:parse({"--pair", "Alice", "Bob"})
          assert.same({pair = {"Alice", "Bob"}}, args)
       end)
@@ -190,55 +190,55 @@ describe("tests related to options", function()
       describe("Multi-count options", function()
          it("handles multi-count option correctly", function()
             local parser = Parser()
-            parser:option("-e", "--exclude", {
+            parser:option "-e" "--exclude" {
                count = "*"
-            })
+            }
             local args = parser:parse({"-efoo", "--exclude=bar", "-e", "baz"})
             assert.same({exclude = {"foo", "bar", "baz"}}, args)
          end)
 
          it("handles not used multi-count option correctly", function()
             local parser = Parser()
-            parser:option("-e", "--exclude", {
+            parser:option "-e" "--exclude" {
                count = "*"
-            })
+            }
             local args = parser:parse({})
             assert.same({exclude = {}}, args)
          end)
 
          it("handles multi-count multi-argument option correctly", function()
             local parser = Parser()
-            parser:option("-e", "--exclude", {
+            parser:option "-e" "--exclude" {
                count = "*",
                args = 2
-            })
+            }
             local args = parser:parse({"-e", "Alice", "Bob", "-e", "Emma", "Jacob"})
             assert.same({exclude = {{"Alice", "Bob"}, {"Emma", "Jacob"}}}, args)
          end)
 
          it("handles multi-count flag correctly", function()
             local parser = Parser()
-            parser:flag("-q", "--quiet", {
+            parser:flag "-q" "--quiet" {
                count = "*"
-            })
+            }
             local args = parser:parse({"-qq", "--quiet"})
             assert.same({quiet = 3}, args)
          end)
 
          it("overwrites old invocations", function()
             local parser = Parser()
-            parser:option("-u", "--user", {
+            parser:option "-u" "--user" {
                count = "0-2"
-            })
+            }
             local args = parser:parse({"-uAlice", "--user=Bob", "--user", "John"})
             assert.same({user = {"Bob", "John"}}, args)
          end)
 
          it("handles not used multi-count flag correctly", function()
             local parser = Parser()
-            parser:flag("-q", "--quiet", {
+            parser:flag "-q" "--quiet" {
                count = "*"
-            })
+            }
             local args = parser:parse({})
             assert.same({quiet = 0}, args)
          end)
@@ -248,7 +248,7 @@ describe("tests related to options", function()
    describe("passing incorrect options", function()
       it("handles lack of required argument correctly", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          assert.has_error(function() parser:parse{"--server"} end, "too few arguments")
       end)
 
@@ -264,30 +264,30 @@ describe("tests related to options", function()
 
       it("handles too many arguments correctly", function()
          local parser = Parser()
-         parser:option("-s", "--server")
+         parser:option "-s" "--server"
          assert.has_error(function() parser:parse{"-sfoo", "bar"} end, "too many arguments")
       end)
 
       it("doesn't accept GNU-like long options when it doesn't need arguments", function()
          local parser = Parser()
-         parser:flag("-q", "--quiet")
+         parser:flag "-q" "--quiet"
          assert.has_error(function() parser:parse{"--quiet=very_quiet"} end, "option '--quiet' does not take arguments")
       end)
 
       it("handles too many invocations correctly", function()
          local parser = Parser()
-         parser:flag("-q", "--quiet", {
+         parser:flag "-q" "--quiet" {
             count = 1,
             overwrite = false
-         })
+         }
          assert.has_error(function() parser:parse{"-qq"} end, "option '-q' must be used at most 1 time")
       end)
 
       it("handles too few invocations correctly", function()
          local parser = Parser()
-         parser:option("-f", "--foo", {
+         parser:option "-f" "--foo" {
             count = "3-4"
-         })
+         }
          assert.has_error(function() parser:parse{"-fFOO", "-fBAR"} end, "option '-f' must be used at least 3 times")
       end)
    end)

src/argparse.lua

@@ -1,7 +1,3 @@
-local Parser, Command, Argument, Option
-
--- Create classes with setters
-do
 local function deep_update(t1, t2)
    for k, v in pairs(t2) do
       if type(v) == "table" then
@@ -14,164 +10,168 @@ do
    return t1
 end
 
+-- A property is a tuple {name, callback}.
+local function new_class(prototype, properties, parent)
+   -- Class is the metatable of its instances.
+   local class = {}
+   class.__index = class
+
+   if parent then
+      class.__prototype = deep_update(deep_update({}, parent.__prototype), prototype)
+   else
+      class.__prototype = prototype
+   end
+
+   local names = {}
+
+   -- Create setter methods and fill set of property names. 
+   for _, property in ipairs(properties) do
+      local name, callback = property[1], property[2]
+
+      class[name] = function(self, value)
+         if not callback(self, value) then
+            self["_" .. name] = value
+         end
+
+         return self
+      end
+
+      names[name] = true
+   end
+
+   function class.__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 then
+               break
+            end
+
+            local arg = select(i, ...)
+
+            if arg ~= nil then
+               self[property[1]](self, arg)
+            end
+         end
+      end
+
+      return self
+   end
+
+   -- If indexing class fails, fallback to its parent.
    local class_metatable = {}
+   class_metatable.__index = parent
 
-   function class_metatable.__call(cls, ...)
+   function class_metatable.__call(self, ...)
-      return setmetatable(deep_update({}, cls.__proto), cls)(...)
+      -- Calling a class returns its instance.
+      -- Arguments are delegated to the instance.
+      local object = deep_update({}, self.__prototype)
+      setmetatable(object, self)
+      return object(...)
    end
 
-   function class_metatable.__index(cls, key)
+   return setmetatable(class, class_metatable)
-      return cls.__parent and cls.__parent[key]
 end
 
-   local function class(proto)
+local function typecheck(name, types, value)
-      local cls = setmetatable({__proto = proto, __parent = {}}, class_metatable)
+   for _, type_ in ipairs(types) do
-      cls.__index = cls
+      if type(value) == type_ then
-      return cls
+         return true
-   end
-
-   local function extend(cls, proto)
-      local new_cls = class(deep_update(deep_update({}, cls.__proto), proto))
-      new_cls.__parent = cls
-      return new_cls
-   end
-
-   local function add_setters(cl, fields)
-      for field, setter in pairs(fields) do
-         cl[field] = function(self, value)
-            setter(self, value)
-            self["_"..field] = value
-            return self
       end
    end
 
-      cl.__call = function(self, ...)
+   error(("bad property '%s' (%s expected, got %s)"):format(name, table.concat(types, " or "), type(value)))
-         local name_or_options
-
-         for i=1, select("#", ...) do
-            name_or_options = select(i, ...)
-
-            if type(name_or_options) == "string" then
-               if self._aliases then
-                  table.insert(self._aliases, name_or_options)
 end
 
-               if not self._aliases or not self._name then
+local function typechecked(name, ...)
-                  self._name = name_or_options
+   local types = {...}
-               end
+   return {name, function(_, value) typecheck(name, types, value) end}
-            elseif type(name_or_options) == "table" then
-               for field in pairs(fields) do
-                  if name_or_options[field] ~= nil then
-                     self[field](self, name_or_options[field])
-                  end
-               end
-            end
 end
 
-         return self
+local aliased_name = {"name", function(self, value)
-      end
+   typecheck("name", {"string"}, value)
+   table.insert(self._aliases, value)
+   -- Do not set _name to value if there is a name already.
+   return self._name
+end}
 
-      return cl
+local aliased_aliases = {"aliases", function(self, value)
-   end
+   typecheck("aliases", {"table"}, value)
-
-   local typecheck = setmetatable({}, {
-      __index = function(self, type_)
-         local typechecker_factory = function(field)
-            return function(_, value)
-               if type(value) ~= type_ then
-                  error(("bad field '%s' (%s expected, got %s)"):format(field, type_, type(value)))
-               end
-            end
-         end
-
-         self[type_] = typechecker_factory
-         return typechecker_factory
-      end
-   })
-
-   local function aliased_name(self, name)
-      typecheck.string "name" (self, name)
-
-      table.insert(self._aliases, name)
-   end
-
-   local function aliased_aliases(self, aliases)
-      typecheck.table "aliases" (self, aliases)
 
    if not self._name then
-         self._name = aliases[1]
+      self._name = value[1]
    end
+end}
+
+local function parse_boundaries(str)
+   if tonumber(str) then
+      return tonumber(str), tonumber(str)
    end
 
-   local function parse_boundaries(boundaries)
+   if str == "*" then
-      if tonumber(boundaries) then
-         return tonumber(boundaries), tonumber(boundaries)
-      end
-
-      if boundaries == "*" then
       return 0, math.huge
    end
 
-      if boundaries == "+" then
+   if str == "+" then
       return 1, math.huge
    end
 
-      if boundaries == "?" then
+   if str == "?" then
       return 0, 1
    end
 
-      if boundaries:match "^%d+%-%d+$" then
+   if str:match "^%d+%-%d+$" then
-         local min, max = boundaries:match "^(%d+)%-(%d+)$"
+      local min, max = str:match "^(%d+)%-(%d+)$"
       return tonumber(min), tonumber(max)
    end
 
-      if boundaries:match "^%d+%+$" then
+   if str:match "^%d+%+$" then
-         local min = boundaries:match "^(%d+)%+$"
+      local min = str:match "^(%d+)%+$"
       return tonumber(min), math.huge
    end
 end
 
-   local function boundaries(field)
+local function boundaries(name)
-      return function(self, value)
+   return {name, function(self, value)
+      typecheck(name, {"number", "string"}, value)
+
       local min, max = parse_boundaries(value)
 
       if not min then
-            error(("bad field '%s'"):format(field))
+         error(("bad property '%s'"):format(name))
       end
 
-         self["_min"..field], self["_max"..field] = min, max
+      self["_min" .. name], self["_max" .. name] = min, max
-      end
+   end}
 end
 
-   local function convert(_, value)
+local add_help = {"add_help", function(self, value)
-      if type(value) ~= "function" then
-         if type(value) ~= "table" then
-            error(("bad field 'convert' (function or table expected, got %s)"):format(type(value)))
-         end
-      end
-   end
-
-   local function argname(_, value)
-      if type(value) ~= "string" then
-         if type(value) ~= "table" then
-            error(("bad field 'argname' (string or table expected, got %s)"):format(type(value)))
-         end
-      end
-   end
-
-   local function add_help(self, param)
    if self._has_help then
       table.remove(self._options)
       self._has_help = false
    end
 
-      if param then
+   if value then
       local help = self:flag()
          :description "Show this help message and exit."
          :action(function()
-               io.stdout:write(self:get_help() .. "\n")
+            print(self:get_help())
             os.exit(0)
-            end)(param)
+         end)
+
+      if value ~= true then
+         help = help(value)
+      end
 
       if not help._name then
          help "-h" "--help"
@@ -179,40 +179,40 @@ do
 
       self._has_help = true
    end
-   end
+end}
 
-   Parser = add_setters(class {
+local Parser = new_class({
    _arguments = {},
    _options = {},
    _commands = {},
    _mutexes = {},
    _require_command = true
 }, {
-      name = typecheck.string "name",
+   typechecked("name", "string"),
-      description = typecheck.string "description",
+   typechecked("description", "string"),
-      epilog = typecheck.string "epilog",
+   typechecked("epilog", "string"),
-      require_command = typecheck.boolean "require_command",
+   typechecked("usage", "string"),
-      usage = typecheck.string "usage",
+   typechecked("help", "string"),
-      help = typecheck.string "help",
+   typechecked("require_command", "boolean"),
-      add_help = add_help
+   add_help
 })
 
-   Command = add_setters(extend(Parser, {
+local Command = new_class({
    _aliases = {}
-   }), {
+}, {
-      name = aliased_name,
+   aliased_name,
-      aliases = aliased_aliases,
+   aliased_aliases,
-      description = typecheck.string "description",
+   typechecked("description", "string"),
-      epilog = typecheck.string "epilog",
+   typechecked("epilog", "string"),
-      target = typecheck.string "target",
+   typechecked("target", "string"),
-      require_command = typecheck.boolean "require_command",
+   typechecked("usage", "string"),
-      action = typecheck["function"] "action",
+   typechecked("help", "string"),
-      usage = typecheck.string "usage",
+   typechecked("require_command", "boolean"),
-      help = typecheck.string "help",
+   typechecked("action", "function"),
-      add_help = add_help
+   add_help
-   })
+}, Parser)
 
-   Argument = add_setters(class {
+local Argument = new_class({
    _minargs = 1,
    _maxargs = 1,
    _mincount = 1,
@@ -220,37 +220,36 @@ do
    _defmode = "unused",
    _show_default = true
 }, {
-      name = typecheck.string "name",
+   typechecked("name", "string"),
-      description = typecheck.string "description",
+   typechecked("description", "string"),
-      target = typecheck.string "target",
+   typechecked("target", "string"),
-      args = boundaries "args",
+   boundaries("args"),
-      default = typecheck.string "default",
+   typechecked("default", "string"),
-      defmode = typecheck.string "defmode",
+   typechecked("defmode", "string"),
-      convert = convert,
+   typechecked("show_default", "boolean"),
-      argname = argname,
+   typechecked("argname", "string", "table"),
-      show_default = typecheck.boolean "show_default"
+   typechecked("convert", "function", "table")
 })
 
-   Option = add_setters(extend(Argument, {
+local Option = new_class({
    _aliases = {},
    _mincount = 0,
    _overwrite = true
-   }), {
+}, {
-      name = aliased_name,
+   aliased_name,
-      aliases = aliased_aliases,
+   aliased_aliases,
-      description = typecheck.string "description",
+   typechecked("description", "string"),
-      target = typecheck.string "target",
+   typechecked("target", "string"),
-      args = boundaries "args",
+   boundaries("args"),
-      count = boundaries "count",
+   boundaries("count"),
-      default = typecheck.string "default",
+   typechecked("default", "string"),
-      defmode = typecheck.string "defmode",
+   typechecked("defmode", "string"),
-      convert = convert,
+   typechecked("show_default", "boolean"),
-      overwrite = typecheck.boolean "overwrite",
+   typechecked("overwrite", "boolean"),
-      action = typecheck["function"] "action",
+   typechecked("argname", "string", "table"),
-      argname = argname,
+   typechecked("convert", "function", "table"),
-      show_default = typecheck.boolean "show_default"
+   typechecked("action", "function")
-   })
+}, Argument)
-end
 
 function Argument:_get_argument_list()
    local buf = {}