Improves the logic to import objects in helpers

[ifsnow]

Q	A
Fixed Issues?	No
Patch: Bug Fix?	No
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link	N/A
Any Dependency Changes?	No
License	MIT

---

In the case of react-native,

import React, { PureComponent } from 'react';

Compiled as below.

var _react = _interopRequireWildcard(_$$_REQUIRE(_dependencyMap[7], "react"));

The below logic(looping) is performed whenever _interopRequireWildcard with react is called.

var newObj = {};

if (obj != null) {
  for (var key in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, key)) {
      var desc = Object.defineProperty && Object.getOwnPropertyDescriptor ? Object.getOwnPropertyDescriptor(obj, key) : {};

      if (desc.get || desc.set) {
        Object.defineProperty(newObj, key, desc);
      } else {
        newObj[key] = obj[key];
      }
    }
  }
}

Generally, We have a lot of components that imports react or react-native. I don't think it's good to check the same object repeatedly on every call. so, I thought it would be better to put cache logic in here.

I counted the number of how many loops are executed to start my production-level App. It may feel like, but it feels like my app is a little faster. :)

Version	Count
Current	11,032
New (Cache)	128

I don't fully understand Babel architecture. Please let me know if I have any mistakes.

I hope this helps.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/11288/

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/11044/

[nicolo-ribaudo]

This makes it more compliant to the node implementation:

// main.mjs

import * as a from "./a.js";
import { aFromB } from "./b.mjs";

console.log(a === aFromB);

// m.mjs

import * as a from "./a.js";

export { a as aFromB };

// a.js

module.exports = { foo: 1 };

[nicolo-ribaudo]

Note that this optimization would only work when using @babel/plugin-transform-runtime, otherwise the map is re-created in every file.

[ifsnow]

@nicolo-ribaudo Thanks for your feedback. I will try something better based on what you said.

[ifsnow]

@nicolo-ribaudo I've modified it to work well in the case you mentioned. Please let me know if there's anything else I need to consider.

[ifsnow]

@nicolo-ribaudo @Andarist @zloirock Thank you all for the feedback.

I realized that there might be no global object. https://github.com/webpack/webpack/blob/master/buildin/global.js#L16

In this case, I modified the cache to not work. I'm sure cache works well in modern development environments.

[ifsnow]

@ljharb Thank you for pointing out what I did not think of.

[ifsnow]

@nicolo-ribaudo @jridgewell @Andarist @zloirock @ljharb @cpojer Do you have plans to merge this PR?

I'm sure this cache feature makes React Native apps run faster. The following table shows the time spent running js bundle at startup.

Device + Engine	Current (ms)	Cache (ms)	Improving
Android 6.0 (32bit) + JSC	3,182	2,990	6%🔻
Android 7.0 (64bit) + JSC	1,118	1,089	2.6%🔻
Android 6.0 (32bit) + Hermes	1,230	964	21.7%🔻
Android 7.0 (64bit) + Hermes	403	367	9%🔻

The following cases are more effective.

• Use many components
• Use low performance devices
• Use Hermes engine

I think we can improve the performance of many React Native apps without any effort. Please review it positively.

[JLHwung]

@ifsnow On the CircleCI failure, please rebase on upstream master.

[ifsnow]

@JLHwung Thanks for your feedback. Rebased my changes on upstream master to clear CircleCI failure. I think Travis CI failure is due to a build system issue (Network timeout).

[nicolo-ribaudo]

Restarted

[ifsnow]

@nicolo-ribaudo Do you have any plans to release the new version? I'm wondering when this fix will be available :)