Add tests for custom __index and __newindex

spec/metamethods_spec.lua

@@ -204,6 +204,92 @@ describe('Metamethods', function()
     end)
   end)
 
+  describe('Custom __index and __newindex', function()
+    describe('Tables', function()
+      local Proxy, fallback, p
+      before_each(function()
+        Proxy = class('Proxy')
+        fallback = {foo = 'bar', common = 'fallback'}
+        Proxy.__index = fallback
+        Proxy.__newindex = fallback
+        Proxy.common = 'class'
+        p = Proxy()
+      end)
+
+      it('uses __index', function()
+        assert.equal(p.foo, 'bar')
+      end)
+
+      it('does not use __index when field exists in class', function()
+        assert.equal(p.common, 'class')
+      end)
+
+      it('uses __newindex', function()
+        p.key = 'value'
+        assert.equal(fallback.key, 'value')
+      end)
+
+      it('does not use __newindex when field exists in class', function()
+        p.common = 'value'
+        assert.equal(p.common, 'value')
+        assert.equal(Proxy.common, 'class')
+        assert.equal(fallback.common, 'fallback')
+      end)
+    end)
+
+    describe('Functions', function()
+      local Namespace, Rectangle, r
+      before_each(function()
+        Namespace = class('Namespace')
+        function Namespace:__index(name)
+          local getter = self.class[name.."Getter"]
+          if getter then return getter(self) end
+        end
+        function Namespace:__newindex(name, value)
+          local setter = self.class[name.."Setter"]
+          if setter then setter(self, value) else rawset(self, name, value) end
+        end
+        Rectangle = class('Rectangle', Namespace)
+        function Rectangle:initialize(x, y, scale)
+          self._scale, self.x, self.y = 1, x, y
+          self.scale = scale
+        end
+        function Rectangle:scaleGetter() return self._scale end
+        function Rectangle:scaleSetter(v)
+          self.x = self.x*v/self._scale
+          self.y = self.y*v/self._scale
+          self._scale = v
+        end
+        function Rectangle:areaGetter() return self.x * self.y end
+        r = Rectangle(3, 4, 2)
+      end)
+
+      it('uses setter', function()
+        assert.equal(r.x, 6)
+        assert.equal(r.y, 8)
+        r.scale = 3
+        assert.equal(r.x, 9)
+        assert.equal(r.y, 12)
+      end)
+
+      it('uses getters', function()
+        assert.equal(r.scale, 2)
+        assert.equal(r.area, 48)
+      end)
+
+      it('updates inherited __index', function()
+        function Namespace.__index() return 42 end
+        assert.equal(r.area, 42)
+        function Rectangle.__index() return 24 end
+        assert.equal(r.area, 24)
+        function Namespace.__index() return 96 end
+        assert.equal(r.area, 24)
+        Rectangle.__index = nil
+        assert.equal(r.area, 96)
+      end)
+    end)
+  end)
+
   describe('Default Metamethods', function()
 
     local Peter, peter