refactor: make computed property wrapping more clear

It wasn't previously clear that the `wrapComputedProperty` behavior is
only invoked for computed properties. This code functions the same, but
makes it easier to see that the computed property wrapping is only
sometimes performed

addon/-private/extensions/with-validation.js

@@ -1,6 +1,9 @@
 import Ember from 'ember';
 
-import wrapComputedProperty from '../wrap-computed-property';
+import {
+  isComputedProperty,
+  wrapComputedProperty
+} from '../wrap-computed-property';
 import { getValidationsFor } from '../validations-for';
 
 const HAS_VALIDATION = new WeakSet();
@@ -31,7 +34,9 @@ export function withExtension(klass) {
       for (let key in validations) {
         const validation = validations[key];
 
-        wrapComputedProperty(constructor, this, meta, validation, key);
+        if (isComputedProperty(meta, key)) {
+          wrapComputedProperty(constructor, this, meta, validation, key);
+        }
 
         validation.run(constructor, key, this[key], 'init');
       }

addon/-private/wrap-computed-property.js

@@ -44,34 +44,37 @@ class ComputedValidatedProperty {
   }
 }
 
-export default function wrapComputedProperty(
+export function isComputedProperty(meta, key) {
+  const possibleDesc = meta.peekDescriptors(key);
+
+  return possibleDesc && possibleDesc.isDescriptor;
+}
+
+export function wrapComputedProperty(
   klass,
   instance,
   meta,
   typeValidators,
   key
 ) {
-  const possibleDesc = meta.peekDescriptors(key);
+  const desc = meta.peekDescriptors(key);
 
-  // Handle the argument being overwritten by a computed property
-  if (possibleDesc && possibleDesc.isDescriptor) {
-    let originalValue = possibleDesc.get(instance, key);
-
-    let validatedProperty = new ComputedValidatedProperty(
-      possibleDesc,
-      klass,
-      originalValue,
-      typeValidators
-    );
-
-    Object.defineProperty(instance, key, {
-      configurable: true,
-      enumerable: true,
-      get() {
-        return validatedProperty.get(instance, key);
-      }
-    });
-
-    meta.writeDescriptors(key, validatedProperty);
-  }
+  let originalValue = desc.get(instance, key);
+
+  let validatedProperty = new ComputedValidatedProperty(
+    desc,
+    klass,
+    originalValue,
+    typeValidators
+  );
+
+  Object.defineProperty(instance, key, {
+    configurable: true,
+    enumerable: true,
+    get() {
+      return validatedProperty.get(instance, key);
+    }
+  });
+
+  meta.writeDescriptors(key, validatedProperty);
 }