Class: WhyClasses::Rules::InvalidInitialState

Inherits:
WhyClasses::Rule show all
Defined in:
lib/why_classes/rules/invalid_initial_state.rb

Overview

A red-flag pattern: initialize leaves a field nil, so the object is invalid until a setter is called after .new. A signal the "object" is really a sequence of function calls in disguise.

Constant Summary

Constants inherited from WhyClasses::Rule

WhyClasses::Rule::H

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from WhyClasses::Rule

autocorrectable?, #call, inherited, #initialize, rule_name, tier

Constructor Details

This class inherits a constructor from WhyClasses::Rule

Class Method Details

.description ⇒ Object 



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# File 'lib/why_classes/rules/invalid_initial_state.rb', line 11

def self.description
  "Object constructed in an invalid state (initialize sets a field to nil, needs a setter first)."
end

Instance Method Details

#on_class(node) ⇒ Object 



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# File 'lib/why_classes/rules/invalid_initial_state.rb', line 15

def on_class(node)
  s = shape(node)
  return if s.name.nil?

  init = s.initialize_method
  return if init.nil?

  writers = s.attr_macros[:attr_writer] + s.attr_macros[:attr_accessor]
  nils = nil_assigned_ivars(init)
  return if nils.empty?

  nils.each do |ivar|
    field = ivar.to_s.delete_prefix("@").to_sym
    next unless writers.include?(field)
    next unless field_read_in_behavior?(s, ivar)

    add_offense(
      node,
      message: "#{s.name}#initialize sets #{ivar} = nil and exposes a setter, so a " \
               "#{s.name} is invalid until `#{field}=` is called.",
      suggestion: "Require #{field} up front instead:\n" \
                  "    def initialize(#{field})\n      @#{field} = #{field}\n    end\n" \
                  "  or drop the object entirely and pass #{field} to a module function."
    )
  end
end