Throw away serialized state if its version doesn't match deserializer

spec/app/window-spec.coffee

@@ -130,3 +130,34 @@ describe "Window", ->
         window.installAtomCommand(commandPath)
         expect(fs.exists(commandPath)).toBeTruthy()
         expect(fs.read(commandPath).length).toBeGreaterThan 1
+
+  describe ".deserialize(state)", ->
+    class Foo
+      @deserialize: ({name}) -> new Foo(name)
+      constructor: (@name) ->
+
+    beforeEach ->
+      registerDeserializer(Foo)
+
+    afterEach ->
+      unregisterDeserializer(Foo)
+
+    it "calls deserialize on the deserializer for the given state object, or returns undefined if one can't be found", ->
+      object = deserialize({ deserializer: 'Foo', name: 'Bar' })
+      expect(object.name).toBe 'Bar'
+      expect(deserialize({ deserializer: 'Bogus' })).toBeUndefined()
+
+    describe "when the deserializer has a version", ->
+      beforeEach ->
+        Foo.version = 2
+
+      describe "when the deserialized state has a matching version", ->
+        it "attempts to deserialize the state", ->
+          object = deserialize({ deserializer: 'Foo', version: 2, name: 'Bar' })
+          expect(object.name).toBe 'Bar'
+
+      describe "when the deserialized state has a non-matching version", ->
+        it "returns undefined", ->
+          expect(deserialize({ deserializer: 'Foo', version: 3, name: 'Bar' })).toBeUndefined()
+          expect(deserialize({ deserializer: 'Foo', version: 1, name: 'Bar' })).toBeUndefined()
+          expect(deserialize({ deserializer: 'Foo', name: 'Bar' })).toBeUndefined()

src/app/window.coffee

@@ -155,7 +155,9 @@ window.unregisterDeserializer = (klass) ->
   delete deserializers[klass.name]
 
 window.deserialize = (state) ->
-  getDeserializer(state)?.deserialize(state)
+  if deserializer = getDeserializer(state)
+    return if deserializer.version? and deserializer.version isnt state.version
+    deserializer.deserialize(state)
 
 window.getDeserializer = (state) ->
   deserializers[state?.deserializer]