这是 Rake 的初稿

# Rakefile

task "third_task", %w[first_task second_task] do
  puts "third task"
end

task "first_task", %w[before_task] do
  puts "first task"
end

task "second_task", %w[before_task] do
  puts "second task"
end

task "before_task" do
  puts "before"
end

让我们来执行 Rake 任务

$> rake third_task
before
first task
second task
third task

这是 Rake 最初如何工作的，让我们再来看看 Rake 脚本内容。

# micro-rake.rb

TASKS = {}

class Task
  def initialize(name, deps, action)
    @name = name
    @deps = deps
    @action = action
  end

  def invoke
    return if @already_run # 避免重复执行任务

    @deps.each do |dep| TASKS[dep].invoke end # 解决依赖问题
    execute                                   # 执行任务
    @already_run = true                       # 标记此任务已执行
  end

  def execute
    @action.call # 在Rakefile里执行block的“task”命令
  end
end

def task(name, deps=[], &block)
  TASKS[name] = Task.new(name, deps, block)
end

load './Rakefile'

ARGV.each do |arg| TASKS[arg].invoke end

$> ruby micro-rake.rb third_task
before
first task
second task
third task