Add Inheritance Rules, Minor Bug Fixes

Attributes previously were not inherited.  This adds the ability
for attributes to be inherited both through classes and modules
through the `@parent` property on the AttributeList.

.rubocop.yml

@@ -1,9 +1,40 @@
-Style/StringLiterals:
-  EnforcedStyle: double_quotes
+AllCops:
+  TargetRubyVersion: 2.3
+
+Metrics/LineLength:
+  Enabled: false
+Metrics/MethodLength:
+  Max: 15
+Metrics/BlockLength:
+  Exclude:
+    - 'spec/*.rb'
+    - 'spec/**/*.rb'
+Metrics/AbcSize:
+  Max: 25
+
+Style/AlignParameters:
+  EnforcedStyle: with_fixed_indentation
+Style/SignalException:
+  EnforcedStyle: only_fail
+Style/AccessModifierIndentation:
+  EnforcedStyle: outdent
+Style/Documentation:
+  Enabled: false
 Style/Encoding:
   Enabled: true
+  EnforcedStyle: always
   AutoCorrectEncodingComment: "# encoding: utf-8\n"
 Style/RegexpLiteral:
   EnforcedStyle: mixed
-Metrics/MethodLength:
-  Max: 15
+Style/StringLiterals:
+  EnforcedStyle: double_quotes
+Style/AlignHash:
+  EnforcedLastArgumentHashStyle: ignore_implicit
+Style/AlignArray:
+  Enabled: false
+Style/IndentArray:
+  Enabled: false
+Style/Alias:
+  EnforcedStyle: prefer_alias_method
+Style/ParallelAssignment:
+  Enabled: false

Gemfile

@@ -1,10 +1,11 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 source "https://rubygems.org"
 
 # These are in here for reasons.
+gem "coveralls"
 gem "pry"
 gem "rubocop"
-gem "coveralls"
 
 gemspec

Rakefile

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require "bundler/gem_tasks"
 require "rspec/core/rake_task"

lib/mixture.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require "set"
 require "time"

lib/mixture/attribute.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   # An attribute for a mixture object.

lib/mixture/attribute_list.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require "set"
 require "forwardable"
@@ -13,7 +14,36 @@ class AttributeList
     # If it quacks like a duck...
     include Comparable
     # Then it must be a duck.
-    delegate [:fetch, :[], :[]=, :key?, :each, :<=>] => :@list
+    delegate [:<=>, :[]=, :to_h] => :@list
+
+    # @!method fetch(key, value = Undefined, &block)
+    #   Fetches the given key from the attribute list.  If the current attribute
+    #   list does not have the key, it passes it up to the parent, if there is
+    #   one.  If there is no parent, it behaves as normal.
+    #
+    #   @param key [::Symbol]
+    #   @param value [::Object]
+    #   @return [Attribute]
+    # @!method [](key)
+    #   Looks up the given key.  If the current attribute list does not have the
+    #   key, it passes it up to the parent, if there is one.  Otherwise, it
+    #   returns the default value for the list (`nil`).
+    #
+    #   @param key [::Symbol]
+    #   @return [Attribute]
+    # @!method key?(key)
+    #   Returns if the attribute exists.  If it doesn't exist on this list,
+    #   it passes it up to the parent.
+    #
+    #   @param key [::Symbol]
+    #   @return [::Boolean]
+    # @!method each(&block)
+    #   Iterates over the attribute list.  If there is a parent, the current
+    #   attribute list is merged into the parent, then iterated over; otherwise,
+    #   it iterates over the current.
+    #
+    #   @return [void]
+    delegate [:fetch, :[], :key?, :keys, :values, :each, :has_key?] => :with_parent
 
     # Returns a set of options used for the attributes.  This isn't
     # used at the moment.
@@ -27,10 +57,18 @@ class AttributeList
     # @return [Hash{Symbol => Array<Proc>}]
     attr_reader :callbacks
 
+    # The parent of this attribute list.  This is "merged" into this attribute
+    # list.
+    attr_reader :parent
+
     # Initializes the attribute list.
-    def initialize
+    #
+    # @param parent [AttributeList] The parent {AttributeList}.  This is used
+    #   primarily for inheritance.
+    def initialize(parent = nil)
       @list = {}
       @options = {}
+      @parent = parent
       @callbacks = Hash.new { |h, k| h[k] = Set.new }
     end
 
@@ -42,5 +80,11 @@ def initialize
     def create(name, options = {})
       @list[name] = Attribute.new(name, self, options)
     end
+
+  protected
+
+    def with_parent
+      @parent ? @list.merge(@parent.with_parent) : @list
+    end
   end
 end

lib/mixture/coerce.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require "mixture/coerce/base"
 require "mixture/coerce/array"
@@ -65,13 +66,11 @@ def self.perform(type, value)
       begin
         block.call(value, to)
       rescue CoercionError
-        raise
+        fail
       rescue StandardError => e
-        raise CoercionError, "#{e.class}: #{e.message}", e.backtrace
+        fail CoercionError, "#{e.class}: #{e.message}", e.backtrace
       end
     end
-
-    # rubocop:disable Metrics/AbcSize
     # rubocop:disable Metrics/MethodLength
 
     # Registers the default coercions.

lib/mixture/coerce/array.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/base.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require "singleton"
 
@@ -101,12 +102,11 @@ def self.coerce_to(to, data = Undefined, &block)
       # @yieldreturn (see .coerce_to)
       # @return [void]
       def self.data_block(data, &block)
-        case
-        when data.is_a?(::Symbol)
+        if data.is_a?(::Symbol)
           proc { |value| value.public_send(data) }
-        when data.is_a?(::Proc)
+        elsif data.is_a?(::Proc)
           data
-        when block_given?
+        elsif block_given?
           block
         else
           fail ArgumentError, "Expected a block, got #{data.inspect}"
@@ -127,9 +127,11 @@ def self.to(type)
       def to(type)
         coercions = self.class.coercions
         coercable = type.inheritable
-                    .find { |ancestor| coercions.key?(ancestor) }
-        fail CoercionError, "Undefined coercion #{self.class.type} " \
-          "=> #{type}" unless coercable
+                        .find { |ancestor| coercions.key?(ancestor) }
+        unless coercable
+          fail CoercionError, "Undefined coercion #{self.class.type} " \
+            "=> #{type}"
+        end
 
         public_send(coercions[coercable])
       end

lib/mixture/coerce/boolean.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/class.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce
@@ -9,8 +10,10 @@ class Class < Base
       coerce_to(Types::Object, Itself)
       coerce_to(Types::Class) do |value, type|
         member = type.options.fetch(:members).first
-        fail CoercionError, "Cannot coerce #{value.class} =>" \
-             " #{member}" unless value.is_a?(member)
+        unless value.is_a?(member)
+          fail CoercionError, "Cannot coerce #{value.class} =>" \
+               " #{member}"
+        end
         value
       end
     end

lib/mixture/coerce/date.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/datetime.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/float.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/hash.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/integer.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/nil.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/object.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce
@@ -13,11 +14,8 @@ class Object < Base
       TryMethods = proc do |*methods|
         proc do |value|
           method = methods.find { |m| value.respond_to?(m) }
-          if method
-            value.public_send(method)
-          else
-            fail CoercionError, "Could not coerce #{value.class}"
-          end
+          fail CoercionError, "Could not coerce #{value.class}" unless method
+          value.public_send(method)
         end
       end
 

lib/mixture/coerce/range.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/rational.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/set.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/string.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/symbol.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/coerce/time.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Coerce

lib/mixture/errors.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   # All mixture errors inherit this.

lib/mixture/extensions.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 require "mixture/extensions/attributable"
 require "mixture/extensions/coercable"

lib/mixture/extensions/attributable.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Extensions
@@ -16,8 +17,10 @@ module ClassMethods
         def attribute(name, options = {})
           name = name.to_s.intern
           attr = attributes.create(name, options)
-          define_method(attr.getter) {     attribute(name)    }
-          define_method(attr.setter) { |v| attribute(name, v) }
+          define_method(attr.getter) {     attribute(name)    } unless
+            options[:wo] || options[:write_only]
+          define_method(attr.setter) { |v| attribute(name, v) } unless
+            options[:ro] || options[:read_only]
           attr
         end
 
@@ -26,7 +29,12 @@ def attribute(name, options = {})
         # @see AttributeList
         # @return [AttributeList]
         def attributes
-          @_attributes ||= AttributeList.new
+          return @_attributes if @_attributes
+          available = ancestors[1..-1]
+                      .select { |c| c.respond_to?(:attributes) }
+                      .first
+          parent = available ? available.attributes : nil
+          @_attributes = AttributeList.new(parent)
         end
       end
 

lib/mixture/extensions/coercable.rb

@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: true
 
 module Mixture
   module Extensions