如何在ruby回溯中获取源和变量值？

Question

这是典型的Ruby on Rails回溯的最后几帧:

以下是Python中典型Nevow回溯的最后几帧:

它不仅仅是网络环境,你可以在ipython和irb之间进行类似的比较.我怎样才能在Ruby中获得更多这类细节？

Answer 1

AFAIK曾经被捕获过,因此抓住它被引发的背景为时已晚.如果你捕获异常的新调用,你可以使用evil.rb的Binding.of_caller来获取调用范围,并且

eval("local_variables.collect { |l| [l, eval(l)] }", Binding.of_caller)

但这是一个非常大的黑客.正确的答案可能是扩展Ruby以允许对调用堆栈进行一些检查.我不确定是否有一些新的Ruby实现允许这样做,但我确实记得对Binding.of_caller的强烈反对,因为它会使优化变得更加困难.

(说实话,我不理解这种反弹:只要解释器​​记录了关于所执行的优化的足够信息,Binding.of_caller应该能够工作,尽管可能很慢.)

更新

好的,我明白了.Longish代码如下:

class Foo < Exception
  attr_reader :call_binding

  def initialize
    # Find the calling location
    expected_file, expected_line = caller(1).first.split(':')[0,2]
    expected_line = expected_line.to_i
    return_count = 5  # If we see more than 5 returns, stop tracing

    # Start tracing until we see our caller.
    set_trace_func(proc do |event, file, line, id, binding, kls|
      if file == expected_file && line == expected_line
        # Found it: Save the binding and stop tracing
        @call_binding = binding
        set_trace_func(nil)
      end

      if event == :return
        # Seen too many returns, give up. :-(
        set_trace_func(nil) if (return_count -= 1) <= 0
      end
    end)
  end
end

class Hello
  def a
    x = 10
    y = 20
    raise Foo
  end
end
class World
  def b
    Hello.new.a
  end
end

begin World.new.b
rescue Foo => e
  b = e.call_binding
  puts eval("local_variables.collect {|l| [l, eval(l)]}", b).inspect
end