Fix: platform inline transformation

[IvanIhnatsiuk]

Summary

I noticed that when using esmodule named import of platform dead code elimination of Platform.OS did not work.

In this PR, I added logic to find to check that Platform.OS was used from require('react-native). That way, it doesn't matter what name the react-native import has.

Changelog:

Before:

import { Platform } from 'react-native';

if (Platform.OS === 'android') {
  // code
}

Transformed:

import { Platform } from 'react-native';

var _reactNative = _$$_REQUIRE(_dependencyMap[4]);

if (_reactNative.Platform.OS !== 'android') {
  // code
}

After:

import { Platform } from 'react-native';

if (Platform.OS === 'android') {
  // code
}

Transformed:

import { Platform } from 'react-native';

var _reactNative = _$$_REQUIRE(_dependencyMap[4]);

if ('android' !== 'android') {
  // code
}

Test plan

Added a test for the case similar to how code looks in the transformed bundle before being passed to the inline plugin. Also tested this in an app bundle and looked for instances of Platform.OS than should be inlined and made sure there was none.

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[IvanIhnatsiuk]

@robhogan Sorry for the tag, but I do not know who can I tag to ask about this PR 😄

Do you have any plans to merge/close this one?

[robhogan]

Hi @IvanIhnatsiuk - sorry this got dropped, I think #1641 might've superseded it? That was released in 0.83.4

[retyui]

@robhogan I've checked it on the latest ver. of react native (0.84.1)

and issue is still exist facebook/react-native#56344 (comment)

yarn why metro-transform-plugins                                             
├─ metro-transform-worker@npm:0.83.5
│  └─ metro-transform-plugins@npm:0.83.5 (via npm:0.83.5)
│
└─ metro@npm:0.83.5
   └─ metro-transform-plugins@npm:0.83.5 (via npm:0.83.5)