Hashie::Extensions::IgnoreRequired mixin for ignoring required constraints

lib/hashie.rb

@@ -12,6 +12,7 @@ module Extensions
     autoload :Coercion,          'hashie/extensions/coercion'
     autoload :DeepMerge,         'hashie/extensions/deep_merge'
     autoload :IgnoreUndeclared,  'hashie/extensions/ignore_undeclared'
+    autoload :IgnoreRequired,    'hashie/extensions/ignore_required'
     autoload :IndifferentAccess, 'hashie/extensions/indifferent_access'
     autoload :MergeInitializer,  'hashie/extensions/merge_initializer'
     autoload :MethodAccess,      'hashie/extensions/method_access'

lib/hashie/extensions/ignore_required.rb

@@ -0,0 +1,42 @@
+module Hashie
+  module Extensions
+    # IgnoreRequired is a simple mixin that silently ignores
+    # required properties on initialization and assignment instead of
+    # raising an error. This is useful when using a building an object
+    # that will eventually be match a Dash but is temporarily incomplete.
+    #
+    # @example
+    #   class Person < Hashie::Dash
+    #
+    #     property :first_name, required: true
+    #     property :last_name, required: true
+    #     property :email
+    #   end
+    #
+    #   class PartialPerson < Person
+    #     include Hashie::Extensions::IgnoreRequired
+    #   end
+    #
+    #   user_data = {
+    #      :first_name => 'Freddy',
+    #   }
+    #
+    #   p = Person.new(user_data) # ArgumentError: The property 'last_name' is required for Person.
+    #
+    #   p = PartialPerson.new(user_data)
+    #   p.last_name = 'Nostrils'
+    #   p.first_name # => 'Freddy'
+    #   p.first_name # => 'Nostrils'
+    #   p.email      # => nil
+    #   p.foo        # => NoMethodError
+    module IgnoreRequired
+      def assert_property_required!(_property, _value)
+        # do nothing
+      end
+
+      def assert_property_set!(_property)
+        # do nothing
+      end
+    end
+  end
+end

spec/hashie/extensions/ignore_required_spec.rb

@@ -0,0 +1,65 @@
+require 'spec_helper'
+
+describe Hashie::Extensions::IgnoreRequired do
+  context 'included in Dash' do
+    class ForgivingDash < Hashie::Dash
+      include Hashie::Extensions::IgnoreRequired
+      property :city,     required: true
+      property :state,    required: true, from: :province
+      property :zip,      required: true
+    end
+
+    subject { ForgivingDash }
+
+    it 'silently ignores required properties on initialization' do
+      expect { subject.new(city: 'New York') }.to_not raise_error
+    end
+
+    it 'raises errors for undefined properties on initialization' do
+      expect { subject.new(city: 'Toronto', province: 'Ontario') }.to raise_error(NoMethodError, /property 'province' is not defined/)
+    end
+
+    it 'requires properties to be declared on assignment' do
+      hash = subject.new(city: 'Toronto')
+      expect { hash.country = 'Canada' }.to raise_error(NoMethodError)
+    end
+
+    it 'requires properties to be declared on access' do
+      hash = subject.new(city: 'Toronto')
+      expect { hash.country }.to raise_error(NoMethodError)
+    end
+  end
+
+  context 'combined with Coercion' do
+    class ForgivingDashWithCoercion < ForgivingDash
+      include Hashie::Extensions::Coercion
+      coerce_key :zip, ->(v) { format('%05d', v) }
+    end
+
+    subject { ForgivingDashWithCoercion }
+
+    it 'works with coerced properties' do
+      expect(subject.new(zip: 501).zip).to eq('00501')
+    end
+
+    context 'with nested, coerced Dashes' do
+      class Address < Hashie::Dash
+        property :number, required: true
+        property :street, required: true
+        property :apartment
+      end
+
+      class ForgivingDashWithAddress < ForgivingDashWithCoercion
+        property :address, required: true
+        coerce_key :address, Address
+      end
+
+      subject { ForgivingDashWithAddress }
+
+      it 'does not work propagate to nested, coercable properties' do
+        address = { street: 'Pennsylvania Avenue' }
+        expect { subject.new(address: address) }.to raise_error(ArgumentError, /property 'number' is required for Address/)
+      end
+    end
+  end
+end