Debugging, Linting and Code Quality

43.1 Debugging

Alternatives: pry / pry-byebug (popular REPL debugger). VS Code and RubyMine have integrated debugging. error_highlight (3.1+) shows exactly where an error happened in the line.

require "debug"            # the default debugger (Ruby 3.1+)
binding.break              # breakpoint (also: debugger)
# commands: n(ext), s(tep), c(ontinue), info, bt (backtrace), p expr, watch @var, break file.rb:10, finish

binding.irb                # drop into an IRB session at this point
p obj                      # quick inspection
pp complex_structure
puts caller.first(5)       # call stack

rdbg app.rb                          # run under the debugger
rdbg -c -- bundle exec rspec         # debug a command
ruby -r debug/open app.rb            # remote debugging (VS Code attaches)

43.2 Linting and Formatting

Standard (standardrb): a zero-config RuboCop wrapper. Ruby LSP formats with RuboCop or Syntax Tree.

Quality tools: Reek (code smells), Flog/Flay (complexity/duplication), RubyCritic (reports), Brakeman (Rails security), bundler-audit (vulnerable gems), SimpleCov (coverage), YARD (documentation).

gem install rubocop rubocop-performance rubocop-rspec
rubocop                       # check
rubocop -a                    # safe autocorrect
rubocop -A                    # all autocorrect
rubocop --auto-gen-config     # create .rubocop_todo.yml for legacy code

# .rubocop.yml
AllCops:
  TargetRubyVersion: 3.3
  NewCops: enable
plugins:
  - rubocop-performance
  - rubocop-rspec
Style/StringLiterals:
  EnforcedStyle: double_quotes
Metrics/MethodLength:
  Max: 15