chore: assign TS migration (#709)

* chore: assign TS migration

* Remove empty line

* Use correct types

* Add FlowFixMe comment

Author: radko93

packages/cli/src/tools/assign.js renamed to packages/cli/src/tools/assign.ts

@@ -4,14 +4,19 @@
  * Similar to Object.assign(), but it doesn't execute getters. This allows us to have
  * lazy properties on an object and still be able to merge them together
  *
- * @flow
  */
 export default function assign(target: Object, ...sources: Object[]) {
   sources.forEach(source => {
-    let descriptors = Object.keys(source).reduce((acc, key) => {
-      acc[key] = Object.getOwnPropertyDescriptor(source, key);
-      return acc;
-    }, {});
+    let descriptors = Object.keys(source).reduce(
+      (acc, key) => {
+        const propertyDescriptor = Object.getOwnPropertyDescriptor(source, key);
+        if (propertyDescriptor !== undefined) {
+          acc[key] = propertyDescriptor;
+        }
+        return acc;
+      },
+      {} as PropertyDescriptorMap,
+    );
     // by default, Object.assign copies enumerable Symbols too
     Object.getOwnPropertySymbols(source).forEach(sym => {
       let descriptor = Object.getOwnPropertyDescriptor(source, sym);

packages/cli/src/tools/config/index.js

@@ -19,6 +19,7 @@ import type {
   UserConfigT,
   DependencyConfigT,
 } from 'types';
+// $FlowFixMe - converted to TS
 import assign from '../assign';
 // $FlowFixMe - converted to TS
 import merge from '../merge';
@@ -46,7 +47,7 @@ function getDependencyConfig(
               : platformConfig.dependencyConfig(
                   root,
                   /* $FlowFixMe - can't figure out which platform's dependency
-                   config to choose */
+                 config to choose */
                   config.dependency.platforms[platform],
                 );
           return dependency;