Add Hashie::Extensions::Dash::AllowList

Extends a Dash with the ability to
accept only predefined values on a property.

#61

5 files changed, 163 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c26a19e..a2b77b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ Any violations of this scheme are considered to be bugs.
 
 * [#523](https://github.com/hashie/hashie/pull/523): Added TOC, ensure a keep-a-changelog formatted CHANGELOG - [@dblock](https://github.com/dblock).
 * [#522](https://github.com/hashie/hashie/pull/522): Added eierlegende Wollmilchsau mascot graphic - [@carolineartz](https://github.com/carolineartz).
+* [#530](https://github.com/hashie/hashie/pull/530): Added Hashie::Extensions::Dash::PredefinedValues - [@caalberts](https://github.com/caalberts).
 * Your contribution here.
 
 ### Changed
diff --git a/README.md b/README.md
index 4280e7b..4cf0214 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,7 @@
   - [PropertyTranslation](#propertytranslation)
   - [Mash and Rails 4 Strong Parameters](#mash-and-rails-4-strong-parameters)
   - [Coercion](#coercion-1)
+  - [PredefinedValues](#predefinedvalues)
 - [Trash](#trash)
 - [Clash](#clash)
 - [Rash](#rash)
@@ -968,6 +969,20 @@ class UserHash < Hashie::Dash
 end
 ```
 
+### PredefinedValues
+
+The `Hashie::Extensions::Dash::PredefinedValues` mixin extends a Dash with
+the ability to accept predefined values on a property.
+
+```ruby
+class UserHash < Hashie::Dash
+  include Hashie::Extensions::PredefinedValues
+
+  property :gender, values: %i[male female prefer_not_to_say]
+  property :age, values: (0..150)
+end
+```
+
 ## Trash
 
 A Trash is a Dash that allows you to translate keys on initialization. It mixes
diff --git a/lib/hashie.rb b/lib/hashie.rb
index 7f88ed4..8f526c4 100644
--- a/lib/hashie.rb
+++ b/lib/hashie.rb
@@ -41,6 +41,7 @@ module Hashie
       autoload :IndifferentAccess, 'hashie/extensions/dash/indifferent_access'
       autoload :PropertyTranslation, 'hashie/extensions/dash/property_translation'
       autoload :Coercion, 'hashie/extensions/dash/coercion'
+      autoload :PredefinedValues, 'hashie/extensions/dash/predefined_values'
     end
 
     module Mash
diff --git a/lib/hashie/extensions/dash/predefined_values.rb b/lib/hashie/extensions/dash/predefined_values.rb
new file mode 100644
index 0000000..2a0b7ca
--- /dev/null
+++ b/lib/hashie/extensions/dash/predefined_values.rb
@@ -0,0 +1,88 @@
+module Hashie
+  module Extensions
+    module Dash
+      # Extends a Dash with the ability to accept only predefined values on a property.
+      #
+      # == Example
+      #
+      #   class PersonHash < Hashie::Dash
+      #     include Hashie::Extensions::Dash::PredefinedValues
+      #
+      #     property :gender, values: [:male, :female, :prefer_not_to_say]
+      #     property :age, values: (0..150) # a Range
+      #   end
+      #
+      #   person = PersonHash.new(gender: :male, age: -1)
+      #   # => ArgumentError: The value '-1' is not accepted for property 'age'
+      module PredefinedValues
+        def self.included(base)
+          base.instance_variable_set(:@values_for_properties, {})
+          base.extend(ClassMethods)
+          base.include(InstanceMethods)
+        end
+
+        module ClassMethods
+          attr_reader :values_for_properties
+
+          def inherited(klass)
+            super
+            klass.instance_variable_set(:@values_for_properties, values_for_properties.dup)
+          end
+
+          def property(property_name, options = {})
+            super
+
+            return unless (predefined_values = options[:values])
+
+            assert_predefined_values!(predefined_values)
+            set_predefined_values(property_name, predefined_values)
+          end
+
+          private
+
+          def assert_predefined_values!(predefined_values)
+            return if supported_type?(predefined_values)
+
+            raise ArgumentError, %(`values` accepts an Array or a Range.)
+          end
+
+          def supported_type?(predefined_values)
+            [::Array, ::Range].any? { |klass| predefined_values.is_a?(klass) }
+          end
+
+          def set_predefined_values(property_name, predefined_values)
+            @values_for_properties[property_name] = predefined_values
+          end
+        end
+
+        module InstanceMethods
+          def initialize(*)
+            super
+
+            assert_property_values!
+          end
+
+          private
+
+          def assert_property_values!
+            self.class.values_for_properties.each_key do |property|
+              value = send(property)
+
+              if value && !values_for_properties(property).include?(value)
+                fail_property_value_error!(property)
+              end
+            end
+          end
+
+          def fail_property_value_error!(property)
+            raise ArgumentError, "Invalid value for property '#{property}'"
+          end
+
+          def values_for_properties(property)
+            self.class.values_for_properties[property]
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/hashie/extensions/dash/predefined_values_spec.rb b/spec/hashie/extensions/dash/predefined_values_spec.rb
new file mode 100644
index 0000000..a84fe80
--- /dev/null
+++ b/spec/hashie/extensions/dash/predefined_values_spec.rb
@@ -0,0 +1,58 @@
+require 'spec_helper'
+
+describe Hashie::Extensions::Dash::PredefinedValues do
+  let(:extended_dash) do
+    Class.new(Hashie::Dash) do
+      include Hashie::Extensions::Dash::PredefinedValues
+
+      property :gender, values: %i[male female prefer_not_to_say]
+      property :age, values: (0..150)
+    end
+  end
+
+  it 'allows value within the predefined list' do
+    valid_dash = extended_dash.new(gender: :male)
+    expect(valid_dash.gender).to eq(:male)
+  end
+
+  it 'rejects value outside the predefined list' do
+    expect { extended_dash.new(gender: :unicorn) }
+      .to raise_error(ArgumentError, %(Invalid value for property 'gender'))
+  end
+
+  it 'accepts a range for predefined list' do
+    expect { extended_dash.new(age: -1) }
+      .to raise_error(ArgumentError, %(Invalid value for property 'age'))
+  end
+
+  it 'allows property to be nil' do
+    expect { extended_dash.new }
+      .not_to raise_error
+  end
+
+  it 'rejects non array or range for predefined list' do
+    expect do
+      class DashWithUnsupportedValueType < Hashie::Dash
+        include Hashie::Extensions::Dash::PredefinedValues
+
+        property :name, values: -> { :foo }
+      end
+    end.to raise_error(ArgumentError, %(`values` accepts an Array or a Range.))
+  end
+
+  let(:subclass) do
+    Class.new(extended_dash) do
+      property :language, values: %i[ruby javascript]
+    end
+  end
+
+  it 'passes property predefined list to subclasses' do
+    expect { subclass.new(gender: :unicorn) }
+      .to raise_error(ArgumentError, %(Invalid value for property 'gender'))
+  end
+
+  it 'allows subclass to define predefined list' do
+    expect { subclass.new(language: :ruby) }
+      .not_to raise_error
+  end
+end