Automatically start the REPL and show trace on an exception to debug.

• Ruby 2.0.0 or later

• Pry(optional)

$ gem install dexc

$ cat t.rb
def m(obj)
  obj.to_s + 1
end

m(0)

$ ruby -rdexc t.rb
 0:lib/dexc.rb:82>     tp.enable
   TracePoint#enable: false
 1:lib/dexc.rb:83>   end
   Dexc#start: false
 2:lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45>       return gem_original_require(path)
   Kernel#gem_original_require: true
 3:lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45>       return gem_original_require(path)
   Kernel#require: true
 4:t.rb:0>
   IO#set_encoding: #<File:t.rb (closed)>
 5:t.rb:0>
   IO#set_encoding: #<File:t.rb (closed)>
 6:t.rb:1> def m(obj)
   Module#method_added: nil
 7:t.rb:2>   obj.to_s + 1
   Fixnum#to_s: "0"
 8:t.rb:2>   obj.to_s + 1
   Exception#initialize: #<TypeError: no implicit conversion of Fixnum into String>
 9:t.rb:2>   obj.to_s + 1
   Class#new: #<TypeError: no implicit conversion of Fixnum into String>
10:t.rb:2>   obj.to_s + 1
   Exception#exception: #<TypeError: no implicit conversion of Fixnum into String>
11:t.rb:2>   obj.to_s + 1
   Exception#backtrace: nil

TypeError: no implicit conversion of Fixnum into String
        from t.rb:2:in `+'
        from t.rb:2:in `m'
        from t.rb:4:in `<main>'

From: t.rb @ line 2 Object#m:

    1: def m(obj)
 => 2:   obj.to_s + 1
    3: end

[1] pry(main)> obj
=> 0
[2] pry(main)> hist[7] # or dexc_hist[7]
=> "0"