ruby

Ruby / Rails Rules

Style

• Match existing style: RuboCop / Standard. Don't reformat unrelated lines.
• Match existing string-quote preference (single vs double).
• Don't add # frozen_string_literal: true unless other files have it.

Output

• Method change → show only the method.
• Class/module change → show only the changed methods. Use # ... rest of class unchanged.
• Don't reprint require lines unless adding new ones.

Rails-Specific

• Match existing controller pattern: thin controller / service objects / form objects.
• Don't add before_action callbacks beyond what siblings use.
• Don't add concerns or service objects unless the codebase uses them.
• Match existing Active Record style (scope vs class methods, where chaining vs Arel).

Migrations

• Never edit a migration that has already been run in production. Create a new one.
• Match existing migration style (change vs up/down).

Tests

• Match existing framework: RSpec vs Minitest. Don't switch.
• For RSpec: match describe/context/it nesting style already in the file.
• Don't add let! or before blocks beyond what's needed for the new test.

Never

• Don't monkey-patch core classes.
• Don't add attr_accessor for things that don't need to be public.
• Don't introduce metaprogramming (define_method, method_missing) into a codebase that doesn't use it.
• Don't change Gem versions unless that's the explicit task.