change x= to *=, add unit tests and improve existing tests

docs/layouts.rst

@@ -117,7 +117,7 @@ You can also **modify** data as they get passed through extends::
 The following operators are supported within evaluating ``extends``
   * ``+=`` will add the giuven number to the inherited number
   * ``-=`` will subtract the given number from the inherited number
-  * ``x=`` will multiply the inherited number by the given number
+  * ``*=`` will multiply the inherited number by the given number
   * ``/=`` will divide the inherited number by the given number
 
 ``+=`` and ``-=`` also support :doc:`/units`
@@ -154,7 +154,7 @@ As you might expect, ``extends`` can be composed multiple times::
     x: += 10    # evaluates to 110
   aristotle:
     extends: plato
-    x: x= 2     # evaluates to 220
+    x: "*= 2"     # evaluates to 220, note that YAML requires quotes here
 
 Yes, ``extends`` has Multiple Inheritance
 -----------------------------------------

lib/squib/layout_parser.rb

@@ -53,7 +53,7 @@ module Squib
             add_parent_child(parent_val, child_val)
           elsif child_val.to_s.strip.start_with?('-=')
             sub_parent_child(parent_val, child_val)
-          elsif child_val.to_s.strip.start_with?('x=')
+          elsif child_val.to_s.strip.start_with?('*=')
             mul_parent_child(parent_val, child_val)
           elsif child_val.to_s.strip.start_with?('/=')
             div_parent_child(parent_val, child_val)
@@ -82,7 +82,7 @@ module Squib
 
     def mul_parent_child(parent, child)
       parent_pixels = Args::UnitConversion.parse(parent, @dpi).to_f
-      child_float = child.sub('x=', '').to_f
+      child_float = child.sub('*=', '').to_f
       parent_pixels * child_float
     end
 

spec/data/layouts/extends-units-mixed.yml

@@ -1,8 +1,12 @@
 parent:
-  x: 0.5in
+  x: 100
   y: 1in
+  width: 200
+  height: 1cm
 
 child:
   extends: parent
   x: += 1in
-  y: -= 0.5in
+  y: -= 1cm
+  width: "*= 1.5"
+  height: /= 4

spec/layout_parser_spec.rb

@@ -206,8 +206,13 @@ describe Squib::LayoutParser do
   it 'does mixed unit conversion when extending' do
     layout = subject.load_layout(layout_file('extends-units-mixed.yml'))
     expect(layout).to eq({
-      'parent' => { 'x' => '0.5in', 'y' => '1in'},
-      'child'  => { 'x' => 450.0, 'y' => 150.0, 'extends' => 'parent' },
+      'parent' => {
+        'x' => 100, 'y' => '1in',
+        'width' => 200, 'height' => '1cm' },
+      'child'  => {
+        'x' => 400.0, 'y' => 181.8897639,
+        'width' => 300.0, 'height' => 29.527559025,
+        'extends' => 'parent' },
     })
   end