Allow Trash to copy properties from others

Trash should be able to copy properties from other properties without
causing a problem. Trash should also, when doing this, not set any
properties that it doesn't define.

3 files changed, 50 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f04a249..365ecfc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,7 @@ scheme are considered to be bugs.
 * [#436](https://github.com/intridea/hashie/pull/436): Ensure that `Hashie::Extensions::IndifferentAccess` injects itself after a non-destructive merge - [@michaelherold](https://github.com/michaelherold).
 * [#437](https://github.com/intridea/hashie/pull/437): Allow codependent properties to be set on Dash - [@michaelherold](https://github.com/michaelherold).
 * [#438](https://github.com/intridea/hashie/pull/438): Fix: `NameError (uninitialized constant Hashie::Extensions::Parsers::YamlErbParser::Pathname)` in `Hashie::Mash.load` - [@onk](https://github.com/onk).
+* [#457](https://github.com/intridea/hashie/pull/457): Fix `Trash` to allow it to copy properties from other properties - [@michaelherold](https://github.com/michaelherold).
 * Your contribution here.
 
 ### Security
diff --git a/lib/hashie/extensions/dash/property_translation.rb b/lib/hashie/extensions/dash/property_translation.rb
index 25b6499..85bfb89 100644
--- a/lib/hashie/extensions/dash/property_translation.rb
+++ b/lib/hashie/extensions/dash/property_translation.rb
@@ -150,6 +150,7 @@ module Hashie
           def []=(property, value)
             if self.class.translation_exists? property
               send("#{property}=", value)
+              super(property, value) if self.class.properties.include?(property)
             elsif self.class.transformation_exists? property
               super property, self.class.transformed_property(property, value)
             elsif property_exists? property
diff --git a/spec/hashie/trash_spec.rb b/spec/hashie/trash_spec.rb
index 20b717c..a5e5d02 100644
--- a/spec/hashie/trash_spec.rb
+++ b/spec/hashie/trash_spec.rb
@@ -265,4 +265,52 @@ describe Hashie::Trash do
       expect(subject.first_name).to eq('Frodo')
     end
   end
+
+  context 'when copying properties from other properties' do
+    it 'retains the original and also sets the copy' do
+      simple = Class.new(Hashie::Trash) do
+        property :id
+        property :copy_of_id, from: :id
+      end
+
+      subject = simple.new(id: 1)
+
+      expect(subject.id).to eq(1)
+      expect(subject.copy_of_id).to eq(1)
+    end
+
+    it 'grabs the default for the original if it is not set' do
+      with_default = Class.new(Hashie::Trash) do
+        property :id, default: 0
+        property :copy_of_id, from: :id
+      end
+
+      subject = with_default.new
+
+      expect(subject.id).to eq(0)
+      expect(subject.copy_of_id).to eq(0)
+    end
+
+    it 'can be a required value' do
+      with_required = Class.new(Hashie::Trash) do
+        property :id
+        property :copy_of_id, from: :id, required: true, message: 'must be set'
+      end
+
+      expect { with_required.new }.to raise_error(ArgumentError, "The property 'copy_of_id' must be set")
+    end
+
+    it 'does not set properties that do not exist' do
+      from_non_property = Class.new(Hashie::Trash) do
+        property :copy_of_value, from: :value
+      end
+
+      subject = from_non_property.new(value: 0)
+
+      expect(subject).not_to respond_to(:value)
+      expect { subject[:value] }.to raise_error(NoMethodError, "The property 'value' is not defined for .")
+      expect(subject.to_h[:value]).to eq(nil)
+      expect(subject.copy_of_value).to eq(0)
+    end
+  end
 end