Bringing back the extends feature

Adding in my own merge key implementation that allows you to bring in
other keys and modfiy the data. Makes moving boxes around easier.

A quasi-revert of 00e8b59144
...but with something useful!

spec/data/easy-circular-extends.yml

@@ -0,0 +1,6 @@
+a: 
+  extends: b
+  x: 50
+b:
+  extends: a
+  x: 150

spec/data/hard-circular-extends.yml

@@ -0,0 +1,9 @@
+a: 
+  extends: c
+  x: 50
+b:
+  extends: a
+  x: 150
+c: 
+  extends: b
+  y: 250

spec/data/multi-extends-single-entry.yml

@@ -1,13 +1,14 @@
-aunt: &aunt
+aunt: 
   a: 101
   b: 102
   c: 103
-uncle: &uncle
+uncle: 
   x: 104
   y: 105
   b: 106
 child:
-  <<: *uncle
-  <<: *aunt
+  extends: 
+    - uncle
+    - aunt
   a: 107
   x: 108

spec/data/multi-level-extends.yml

@@ -1,10 +1,10 @@
-frame: &frame
+frame: 
   x: 38
   y: 38
-title: &title
-  <<: *frame
+title:
+  extends: frame
   y: 50
   width: 100
-subtitle: 
-  <<: *title
+subtitle:
+  extends: title
   y: 150

spec/data/pre-extends.yml

@@ -0,0 +1,7 @@
+title:
+  extends: frame
+  y: 50
+  width: 100
+frame: 
+  x: 38
+  y: 38

spec/data/self-circular-extends.yml

@@ -0,0 +1,3 @@
+a: 
+  extends: a
+  x: 50

spec/data/single-extends.yml

@@ -1,7 +1,7 @@
-frame: &frame
+frame: 
   x: 38
   y: 38
 title:
-  <<: *frame
+  extends: frame
   y: 50
   width: 100

spec/data/single-level-multi-extends.yml

@@ -1,12 +1,12 @@
-frame: &frame
+frame: 
   x: 38
   y: 38
 title:
-  <<: *frame
+  extends: frame
   y: 50
   width: 100
 title2:
-  <<: *frame
+  extends: frame
   x: 75
   y: 150
   width: 150

spec/deck_spec.rb

@@ -68,6 +68,24 @@ describe Squib::Deck do
               'y' => 38, 
               },
             'title' => {
+              'extends' => 'frame',
+              'x' => 38, 
+              'y' => 50, 
+              'width' => 100,
+              }
+            }
+          )
+    end
+
+    it "applies the extends regardless of order" do
+      d = Squib::Deck.new(layout: test_file('pre-extends.yml')) 
+      expect(d.layout).to \
+        eq({'frame' => {
+              'x' => 38, 
+              'y' => 38, 
+              },
+            'title' => {
+              'extends' => 'frame',
               'x' => 38, 
               'y' => 50, 
               'width' => 100,
@@ -84,11 +102,13 @@ describe Squib::Deck do
               'y' => 38, 
               },
             'title' => {
+              'extends' => 'frame',
               'x' => 38, 
               'y' => 50, 
               'width' => 100,
               },
             'title2' => {
+              'extends' => 'frame',
               'x' => 75, 
               'y' => 150, 
               'width' => 150,
@@ -111,6 +131,7 @@ describe Squib::Deck do
               'b' => 106, 
               },
             'child' => {
+              'extends' => ['uncle','aunt'],
               'a' => 107, # my own
               'b' => 102, # from the younger aunt
               'c' => 103, # from aunt
@@ -129,11 +150,13 @@ describe Squib::Deck do
               'y' => 38, 
               },
             'title' => {
+              'extends' => 'frame',
               'x' => 38, 
               'y' => 50, 
               'width' => 100,
               },
             'subtitle' => {
+              'extends' => 'title',
               'x' => 38,
               'y' => 150, 
               'width' => 100,
@@ -142,6 +165,24 @@ describe Squib::Deck do
           )
     end
 
+    it "fails on a self-circular extends" do
+      file = test_file('self-circular-extends.yml')
+      expect { Squib::Deck.new(layout: file) }.to \
+        raise_error(RuntimeError, "Invalid layout: circular extends with 'a'")
+    end
+
+    it "fails on a easy-circular extends" do
+      file = test_file('easy-circular-extends.yml')
+      expect { Squib::Deck.new(layout: file) }.to \
+        raise_error(RuntimeError, "Invalid layout: circular extends with 'a'")
+    end
+
+    it "hard on a easy-circular extends" do
+      file = test_file('hard-circular-extends.yml')
+      expect { Squib::Deck.new(layout: file) }.to \
+        raise_error(RuntimeError, "Invalid layout: circular extends with 'a'")
+    end
+
   end
 
 end