Initial attempt at basic 'step' and 'next' commands

Based on set_trace_func and similar logic to stdlib's debug.rb.

.gitignore

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+*.gem
+*.rbc
+.bundle
+.config
+.yardoc
+Gemfile.lock
+InstalledFiles
+_yardoc
+coverage
+doc/
+lib/bundler/man
+pkg
+rdoc
+spec/reports
+test/tmp
+test/version_tmp
+tmp

Gemfile

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+source 'http://rubygems.org'
+
+# Specify your gem's dependencies in pry-nav.gemspec
+gemspec

README.md

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+pry-nav
+=======
+
+_Simple execution control in Pry_
+
+Adds **step** and **next** commands to your [Pry][pry]
+console. Makes for a simple but ghetto debugger.
+
+Note: In order to get the correct flow control, `Pry.start` is overriden. Use at
+your own risk.
+
+
+## Acknowledgments
+
+- Ruby stdlib [debug.rb][debug.rb]
+- [@Mon-Ouie][Mon-Ouie]'s [pry_debug][pry_debug]
+
+
+## TODO
+
+- Thread safety
+- Compatibility with [pry-remote][pry-remote]
+
+
+[pry]:         http://pry.github.com
+[debug.rb]:    https://github.com/ruby/ruby/blob/trunk/lib/debug.rb
+[Mon-Ouie]:    https://github.com/Mon-Ouie
+[pry_debug]:   https://github.com/Mon-Ouie/pry_debug
+[pry-remote]:  https://github.com/Mon-Ouie/pry-remote

Rakefile

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+#!/usr/bin/env rake
+require "bundler/gem_tasks"

lib/pry-nav.rb

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+require 'pry-nav/version'
+require 'pry-nav/pry_ext'
+require 'pry-nav/commands'
+require 'pry-nav/tracer'

lib/pry-nav/commands.rb

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+require 'pry'
+
+module PryNav
+  Commands = Pry::CommandSet.new do
+    command 'step', 'Step execution into the next line or method.' do |steps|
+      breakout_navigation :step, steps
+    end
+
+    command 'next', 'Execute the next line within the same stack frame.' do |lines|
+      breakout_navigation :next, lines
+    end
+
+    alias_command 'n', 'next'
+    alias_command 's', 'step'
+
+    helpers do
+      def breakout_navigation(action, times)
+        _pry_.binding_stack.clear     # Clear the binding stack.
+        throw :breakout_nav, {        # Break out of the REPL loop and
+          action: action,             #   signal the tracer.
+          times:  times
+        }
+      end
+    end
+  end
+end
+
+Pry.commands.import PryNav::Commands

lib/pry-nav/pry_ext.rb

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+require 'pry'
+
+class << Pry
+  alias_method :start_existing, :start
+
+  def start(target = TOPLEVEL_BINDING, options = {})
+    PryNav::Tracer.new(options) do
+      start_existing(target, options)
+    end
+  end
+end

lib/pry-nav/tracer.rb

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+require 'pry'
+
+module PryNav
+  class Tracer
+    FILE = File.expand_path(__FILE__)
+
+    def initialize(pry_start_options = {}, &block)
+      @step_in_lines = -1                      # Break after this many lines
+      @frames_when_stepping = nil              # Only break at this frame level
+      @frames = []                             # Traced stack frames
+      @pry_start_options = pry_start_options   # Options to use for Pry.start
+
+      run &block
+    end
+
+    def run(&block)
+      start    # Set the trace function
+
+      return_value = nil
+      command = catch(:breakout_nav) do      # Coordinate with PryNav::Commands
+        return_value = yield
+        {}    # Nothing thrown == no navigational command
+      end
+
+      process_command command
+
+      return_value
+    end
+
+    def start
+      set_trace_func method(:tracer).to_proc
+    end
+
+    def stop
+      set_trace_func nil
+    end
+
+    def process_command(command = {})
+      times = (command[:times] || 1).to_i
+      times = 1 if times <= 0
+
+      case command[:action]
+      when :step
+        @step_in_lines = times
+        @frames_when_stepping = nil
+      when :next
+        @step_in_lines = times
+        @frames_when_stepping = @frames.size
+      else
+        stop
+      end
+    end
+
+
+   private
+
+    def tracer(event, file, line, id, binding, klass)
+      # Ignore traces inside pry-nav code
+      return if (file && File.expand_path(file) == FILE)
+
+      case event
+      when 'line'
+        # Are we stepping? Or continuing by line ('next') and we're at the right
+        # frame? Then decrement our line counter cause this line counts.
+        if !@frames_when_stepping || @frames.size == @frames_when_stepping
+          @step_in_lines -= 1
+          @step_in_lines = -1 if @step_in_lines < 0
+
+        # Did we go up a frame and not break for a 'next' yet?
+        elsif @frames.size < @frames_when_stepping
+          @step_in_lines = 0   # Break right away
+        end
+
+        # Break on this line?
+        Pry.start(binding, @pry_start_options) if @step_in_lines == 0
+
+      when 'call', 'class'
+        @frames.unshift [binding, file, line, id]   # Track entering a frame
+
+      when 'return', 'end'
+        @frames.shift                          # Track leaving a stack frame
+      end
+    end
+  end
+end

lib/pry-nav/version.rb

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+module PryNav
+  VERSION = '0.0.1'
+end

pry-nav.gemspec

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+# -*- encoding: utf-8 -*-
+
+require File.expand_path('../lib/pry-nav/version', __FILE__)
+
+Gem::Specification.new do |gem|
+  gem.name          = 'pry-nav'
+  gem.version       = PryNav::VERSION
+  gem.author        = 'Gopal Patel'
+  gem.email         = 'nixme@stillhope.com'
+  gem.license       = 'MIT'
+  gem.homepage      = 'https://github.com/nixme/pry-nav'
+  gem.summary       = 'Simple execution navigation for Pry.'
+  gem.description   = "Turn Pry into a primitive debugger. Adds 'step' and 'next' commands to control execution."
+
+  gem.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
+  gem.files         = `git ls-files`.split("\n")
+  gem.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
+  gem.require_paths = ["lib"]
+
+  # Dependencies
+  gem.required_ruby_version = '>= 1.9.2'
+  gem.add_runtime_dependency 'pry', '~> 0.9.7.4'
+end