Using Pry outside of the REPL

pry_outside_the_repl.rb

require 'pry'

def a() b end
def b() c end
def c() x = 1; binding; end

io = Object.new
io.instance_eval { @printed = [] }
def io.printed() @printed.tap { @printed = [] } end
def io.readline(prompt) nil end
def io.print(str) @printed << str; nil end

pry = Pry.new(
  input:         io,
  output:        io,
  output_prefix: '',
  prompt:        [proc { '> ' }, proc { '* ' }],
  target:        a(),
  auto_indent:   true,
)
indent = Pry::Indent.new pry

repl = Object.new
repl.define_singleton_method :eval do |str|
  vars = { raw_input: str }
  str += "\n" unless str.end_with? "\n"
  indent.reset if pry.eval_string.empty?
  vars[:prev_prompt]      = pry.select_prompt
  vars[:prev_indentation] = pry.config.auto_indent ? indent.current_prefix.dup : ''
  vars[:cooked_input]     = str.dup
  vars[:alive]            = pry.eval(pry.config.auto_indent ? indent.indent(str) : str) # The real eval is here
  vars[:next_prompt]      = pry.select_prompt
  vars[:next_indentation] = pry.config.auto_indent ? indent.current_prefix.dup : ''
  vars[:is_command]       = ::Pry.current[:pry_cmd_result].command?
  vars[:retval]           = ::Pry.current[:pry_cmd_result].retval
  vars[:printed]          = io.printed
  vars
end

repl.eval "def omg"  
# => {:raw_input=>"def omg",
#     :prev_prompt=>"> ",
#     :prev_indentation=>"",
#     :cooked_input=>"def omg\n",
#     :alive=>true,
#     :next_prompt=>"* ",
#     :next_indentation=>"  ",
#     :is_command=>false,
#     :retval=>nil,
#     :printed=>[]}
repl.eval "1+1"      
# => {:raw_input=>"1+1",
#     :prev_prompt=>"* ",
#     :prev_indentation=>"  ",
#     :cooked_input=>"1+1\n",
#     :alive=>true,
#     :next_prompt=>"* ",
#     :next_indentation=>"  ",
#     :is_command=>false,
#     :retval=>nil,
#     :printed=>[]}
repl.eval "end"      
# => {:raw_input=>"end",
#     :prev_prompt=>"* ",
#     :prev_indentation=>"  ",
#     :cooked_input=>"end\n",
#     :alive=>true,
#     :next_prompt=>"> ",
#     :next_indentation=>"",
#     :is_command=>false,
#     :retval=>nil,
#     :printed=>[":omg\n"]}

repl.eval "omg"     
# => {:raw_input=>"omg",
#     :prev_prompt=>"> ",
#     :prev_indentation=>"",
#     :cooked_input=>"omg\n",
#     :alive=>true,
#     :next_prompt=>"> ",
#     :next_indentation=>"",
#     :is_command=>false,
#     :retval=>nil,
#     :printed=>["2\n"]}

repl.eval "x + 5"
# => {:raw_input=>"x + 5",
#     :prev_prompt=>"> ",
#     :prev_indentation=>"",
#     :cooked_input=>"x + 5\n",
#     :alive=>true,
#     :next_prompt=>"> ",
#     :next_indentation=>"",
#     :is_command=>false,
#     :retval=>nil,
#     :printed=>["6\n"]}

require 'json'
repl.eval "ls -l"
# => {:raw_input=>"ls -l",
#     :prev_prompt=>"> ",
#     :prev_indentation=>"",
#     :cooked_input=>"ls -l\n",
#     :alive=>true,
#     :next_prompt=>"> ",
#     :next_indentation=>"",
#     :is_command=>true,
#     :retval=>void,
#     :printed=>["x = 1\n"]}

This is helpful! I also noticed that I could call pry_instance.evaluate_ruby("1 + 1") which seems to almost be intentional as a public method.