Another DSL in lua, for Vasiliy

dsl.lua

print"TABLE"

function directory(path)
    print("directory", path)

    return function(attrs)
	for key,value in pairs(attrs) do
	    print("", key, value)
	end
    end
end

directory "/etc/" {
    owner  = "root";
    group  = "wheel";
    mode   = "0755";
    action = "create";
}

print"WITHOUT ="

function directory(path)
    print("directory", path)

    return function(attrs)
	for _,attr in pairs(attrs) do
	    key, value = next(attr)
	    print("", key, value)
	end
    end
end

function owner(value)   return { owner  = value } end
function group(value)   return { group  = value } end
function mode(value)    return { mode   = value } end
function action(value)  return { action = value } end

directory "/etc/" {
    owner  "root";
    group  "wheel";
    mode   "0755";
    action "create";
}

print "LESS TYPING"

function ConfigBlock(type, ...)
    _G[type] = function (name)
	print(type, name)
	return function(attrs)
	    for _,attr in pairs(attrs) do
		key, value = next(attr)
		print("", key, value)
	    end
	end
    end

    for _,key in ipairs{...} do
	_G[key] = function (value)
	    return { [key] = value }
	end
    end
end

ConfigBlock("directory", "owner", "group", "mode", "action")

directory "/etc/" {
    owner  "root";
    group  "wheel";
    mode   "0755";
    action "create";
}

-- wipe globals away
for _,v in ipairs{"directory", "owner", "group", "mode", "action"} do
    _G[v] = nil
end

print "NO GLOBALS, LOAD DATA"

env = {}

function ConfigBlock(type, ...)
    env[type] = function (name)
	print(type, name)
	return function(attrs)
	    for _,attr in pairs(attrs) do
		key, value = next(attr)
		print("", key, value)
	    end
	end
    end

    for _,key in ipairs{...} do
	env[key] = function (value)
	    return { [key] = value }
	end
    end
end

function ConfigLoad(loader, config)
    local cfg = assert(loader(config))

    assert(setfenv(cfg, env))

    cfg()
end

ConfigBlock("directory", "owner", "group", "mode", "action")

-- ConfigLoad(loadfile, "filename") would load cfg from file, for
-- sake of example, this loads from a string
ConfigLoad(loadstring, [[
directory "/etc/" {
    owner  "root";
    group  "wheel";
    mode   "0755";
    action "create";
}
]])

print "OOPS!"

env = {}

function ConfigBlock(type, ...)
    env[type] = function (name)
	print(type, name)
	return function(attrs)
	    for _,attr in pairs(attrs) do
		key, value = next(attr)
		print("", key, value)
	    end
	end
    end

    for _,key in ipairs{...} do
	env[key] = function (value)
	    return { [key] = value }
	end
    end
end

function ConfigLoad(loader, config)
    local cfg = assert(loader(config))

    assert(setfenv(cfg, env))

    cfg()
end

ConfigBlock("directory", "owner", "group", "mode", "action")
ConfigBlock("phone", "model", "colour")

-- ConfigLoad(loadfile, "filename") would load cfg from file, for
-- sake of example, this loads from a string
ConfigLoad(loadstring, [[
directory "/etc/" {
    owner  "root";
    group  "wheel";
    mode   "0755";
    action "create";
    colour "black";
}
phone "class" {
    model  "1.2";
    colour "black";
    mode   "0755";
}
]])

print "AAH, BETTER"

env = setmetatable({}, {
    __index = function (t, key)
	return function (value)
	    return { [key] = value }
	end
    end
})

function ConfigBlock(type, ...)
    local allowed = {}
    for _,v in ipairs{...} do
	allowed[v] = true
    end
    env[type] = function (name)
	print(type, name)
	return function(attrs)
	    for _,attr in pairs(attrs) do
		key, value = next(attr)
		assert(allowed[key], type.." does not support attribute "..key)
		print("", key, value)
	    end
	end
    end
end

function ConfigLoad(loader, config)
    local cfg = assert(loader(config))

    assert(setfenv(cfg, env))

    local ok, emsg = xpcall(cfg, debug.traceback)

    if not ok then
	print("config syntax error!\n"..emsg)
    end
end

ConfigBlock("directory", "owner", "group", "mode", "action")
ConfigBlock("phone", "model", "colour")

-- ConfigLoad(loadfile, "filename") would load cfg from file, for
-- sake of example, this loads from a string
ConfigLoad(loadstring, [[
directory "/etc/" {
    owner  "root";
    group  "wheel";
    mode   "0755";
    action "create";
}
phone "class" {
    mode   "0755";
}
]])