Recursively inspect Exception#cause to trace where the error condition originated.

0_cause.rb

name = ->(i){ "method_#{i}" }
methods = 10.times.map do |i|
  define_method(name[i]) do
    if i == 0
      raise "Top level error from #{name[i]}"
    else
      begin
        send name[i - 1]
      rescue
        raise "Error from rescue in #{name[i]}"
      end
    end
  end
end

def explain(error, depth: 0)
  print("  " * depth)
  p error
  explain(error.cause, depth: depth + 1) if error.cause
end

begin
  send(methods[-1])
rescue => e
  explain(e)
end

1_output.txt

#<RuntimeError: Error from rescue in method_9>
  #<RuntimeError: Error from rescue in method_8>
    #<RuntimeError: Error from rescue in method_7>
      #<RuntimeError: Error from rescue in method_6>
        #<RuntimeError: Error from rescue in method_5>
          #<RuntimeError: Error from rescue in method_4>
            #<RuntimeError: Error from rescue in method_3>
              #<RuntimeError: Error from rescue in method_2>
                #<RuntimeError: Error from rescue in method_1>
                  #<RuntimeError: Top level error from method_0>