pry_debug.rb

require 'pry'

module PryDebug
  class FileBreakpoint < Struct.new(:id, :file, :line)
    def to_s
      "breakpoint #{id} at #{file}:#{line}"
    end

    def is_at?(other_file, other_line)
      other_file.end_with?(file) && other_line == line
    end
  end

  Commands = Pry::CommandSet.new do
    command "breakpoint", "adds a breakpoint" do |argument|
      if argument =~ /(.+):(\d+)/
        file, line = $1, $2.to_i

        if other = PryDebug.breakpoints.find { |bp| bp.is_at?(file, line) }
          output.puts "breakpoint #{other.id} is already located at #{argument}"
        else
          bp = PryDebug.add_breakpoint(file, line)
          output.puts "adedd #{bp}"
        end
      else
        output.puts "usage: breakpoint FILE:LINE"
        output.puts
        output.puts "FILE can be foo.rb or /full/path/to/foo.rb"
      end
    end

    command "file", "sets the file to start the debugger at" do |file|
      PryDebug.file = file
      output.puts "debugged file set to #{file}"
    end

    command "run", "starts the debugger" do |arg|
      if arg
        PryDebug.file = arg
      end

      if PryDebug.file and File.exist? PryDebug.file
        throw :start_debugging!, :now!
      else
        output.puts "error: file does not exist: #{PryDebug.file}"
        output.puts "create it or set a new file using the 'file' command."
      end
    end
  end

  ShortCommands = Pry::CommandSet.new Commands do
    alias_command "b", "breakpoint"
    alias_command "bp", "breakpoint"

    alias_command "r", "run"
  end

  @breakpoints = []
  @file        = nil

  class << self
    attr_reader :breakpoints
    attr_accessor :file
  end

  module_function
  def start
    should_start = catch(:start_debugging!) do
      Pry.start(TOPLEVEL_BINDING, :commands => ShortCommands)
    end

    if should_start == :now!
      set_trace_func proc { |*args| PryDebug.trace_func(*args) }
      load PryDebug.file
    end
  end

  def trace_func(event, file, line, method, binding, class_name)
    case event
    when 'line'
      if bp = PryDebug.breakpoints.find { |bp| bp.is_at?(file, line) }
        puts "reached #{bp}"
        Pry.start(binding, :commands => ShortCommands)
      end
    end
  end

  def add_breakpoint(file, line)
    bp = FileBreakpoint.new(PryDebug.breakpoints.size, file, line)
    PryDebug.breakpoints << bp
    bp
  end
end

if $PROGRAM_NAME == __FILE__
  PryDebug.start
end