Fix duplicate Platform.select key inlining

Author: OskarEichler

packages/react-native-babel-preset/src/__tests__/inline-platform-plugin-test.js

@@ -479,6 +479,10 @@ describe('Platform.select', () => {
     expect(select('{ios() { return 1; }}')).toContain('function');
   });
 
+  test('uses the last definition of a duplicate key', () => {
+    expect(select('{ios: 1, ios: 2}')).toContain('const value=2');
+  });
+
   test('does not inline computed keys', () => {
     expect(select('{[key]: 1, default: 2}')).toContain('Platform.select');
   });

packages/react-native-babel-preset/src/inline-platform-plugin.js

@@ -430,7 +430,9 @@ module.exports = function inlinePlatformPlugin(
     key /*: string */,
     fallback /*: () => Node */,
   ) /*: Node */ {
-    for (const property of objectExpression.properties) {
+    // Object literal evaluation keeps the last definition of a duplicate key.
+    for (let i = objectExpression.properties.length - 1; i >= 0; i--) {
+      const property = objectExpression.properties[i];
       if (!t.isObjectProperty(property) && !t.isObjectMethod(property)) {
         continue;
       }