Debugging the Unknown - A script to help bring clarity to complex domains.

README.md

Debugging the Unknown

When exploring a new Ruby codebase, I have a pattern of using caller to understand the callstack and build out a visual representation - E.G:

.
└── ApplicationController/
    └── UsersController#create/
        └── UsersService.create/
            ├── UsersService::UsersCreate#call/
            │   ├── UsersService::UsersValidator#validate
            │   └── MetricsService.increment_new_users
            └── UsersService.build_create_response

Getting Started

• Put a breakpoint somewhere.
• Get the current callstack via caller.
• Collect callstack via: data = callee.reject { |l| l.include?("/gems/") }
• Dump the callstack via: puts Base64.encode64(Marshal.dump(data))
• Paste the data into a file next to the script with the name: callee-to-tree.txt.
• Execute the script: ./callee-to-tree.rb.
• Format the indentation such that invoked methods are nested 1 level deeper than the callee.
• Paste the output to an ASCII tree maker like https://tree.nathanfriend.com/.

Tips

• Keep a plain version of your output so that you can add to it easily as you explore more parts of the codebase and regenerate a new tree.
• Keep a file per flow (Users Create, Users Delete, etc).

call-to-tree.rb

#!/usr/bin/env ruby

require 'base64'

class CalleeToTree
  def build_stack
    locs = load_callers!

    locs.reject! { |p| p.include?('/gems/') }

    locs.reverse!

    indent = 0
    tree = locs.each_with_object([]) do |l, memo|
      fq_path, fq_loc = l.split(" ")
      path, line_number, _extra = fq_path.split(":")
      path.gsub!('/home/bt/', '')

      loc = fq_loc.gsub(/[`'"<>]/, '')

      if loc.include?('block')
        indent += 1
      elsif indent > 0
        indent -= 1
      end

      padding = '  ' * indent
      memo << "#{padding}#{loc} - #{path}:#{line_number}"
    end

    tree
  end

  def load_callers!
    contents = File.read("callstack.txt")
    ::Marshal.load(Base64.decode64(contents))
  end

  def print(data)
    puts data
  end

  class << self
    def print_callers
      util = self.new
      callers = util.build_stack
      util.print(callers)
    end
  end
end

if __FILE__ == $PROGRAM_NAME
  puts CalleeToTree.print_callers
end