耙异常管理答案

【问题标题】：Rake exception management耙异常管理
【发布时间】：2016-01-20 18:50:38
【问题描述】：

考虑这个 Rake 任务：

namespace :foo do
  task :bar do
    begin
      raise 'foo'
    rescue RuntimeError => ex
      raise ex.class, 'bar', ex.backtrace
    end
  end
end

结果如下：

rake aborted!
bar
/home/vagrant/proj/lib/tasks/foo.rake:52:in `block (2 levels) in <top (required)>'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `load'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `block in load'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:240:in `load_dependency'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `load'
-e:1:in `<main>'
foo
/home/vagrant/proj/lib/tasks/foo.rake:52:in `block (2 levels) in <top (required)>'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `load'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `block in load'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:240:in `load_dependency'
/home/vagrant/.gem/ruby/2.3.0/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `load'
-e:1:in `<main>'
Tasks: TOP => foo:bar
(See full trace by running task with --trace)

如您所见，原始异常 (foo) 和新异常 (bar) 都有。这是为什么？我本以为 foo 异常已被妥善救出，不会出现在这里。

【问题讨论】：

标签： ruby-on-rails ruby rake rake-task

【解决方案1】：

原来的例外 (foo) 都不存在。

瑞克文件：

namespace :foo do
  task :bar do
    begin
      raise "message from foo"
    rescue RuntimeError => ex
      puts "#{ex.message}. foo is rescued"             # <= 1st
      raise ex.class, 'message from bar', ex.backtrace # <= 2nd
    end
  end
end

输出：

message from foo. foo is rescued # <= 1st
rake aborted!
message from bar # <= 2nd
/home/vagrant/Rakefile:4:in `block (2 levels) in <top (required)>'
message from foo # <= from backtrace
/home/vagrant/Rakefile:4:in `block (2 levels) in <top (required)>'
Tasks: TOP => foo:bar
(See full trace by running task with --trace)

【讨论】：

感谢您的回答@yhirano55。但是，恐怕我仍然不明白为什么第一个异常的消息会在回溯中？据我所知，这不是标准的 Ruby 行为？