Preserve Platform.select initializer side effects (#1903) - #1929
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Summary:
Metro replaces `Platform.select({...})` with the selected property during production transforms. JavaScript evaluates every object property initializer before calling `Platform.select`, so this can silently remove side effects from non-selected properties.
For example:
```js
Platform.select({
ios: selected(),
android: discarded(),
});
```
OR
```js
Platform.select({
ios() {
selected()
},
android: discarded(),
});
```
JavaScript would run both side effects, `selected()` and `discarded()`. The plugin's current behavior removes `discarded` on iOS however.
This fix preserves both side effects by testing for purity. `findProperty` also clones the selected `ObjectMethod` before calling `t.toExpression`, since `toExpression` mutates the node in place and bailing out on an impure sibling would otherwise leave the original AST mutated (e.g. `ios() {}` becoming `function () {}`), producing invalid output.
Changelog:
```
- **[Fix]**: Preserve side effects from discarded `Platform.select` property initializers
```
Test Plan: Added regression tests, and ensured existing tests, linter and formatter pass. js1 test inline-plugin-test.js -- 64 passed. Verified the ObjectMethod bailout case emits the source unchanged instead of invalid JS.
Differential Revision: D119919582
Pulled By: vzaidman
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Summary:
Metro replaces
Platform.select({...})with the selected property during production transforms. JavaScript evaluates every object property initializer before callingPlatform.select, so this can silently remove side effects from non-selected properties.For example:
OR
JavaScript would run both side effects,
selected()anddiscarded(). The plugin's current behavior removesdiscardedon iOS however.This fix preserves both side effects by testing for purity.
findPropertyalso clones the selectedObjectMethodbefore callingt.toExpression, sincetoExpressionmutates the node in place and bailing out on an impure sibling would otherwise leave the original AST mutated (e.g.ios() {}becomingfunction () {}), producing invalid output.Changelog:
Test Plan: Added regression tests, and ensured existing tests, linter and formatter pass. js1 test inline-plugin-test.js -- 64 passed. Verified the ObjectMethod bailout case emits the source unchanged instead of invalid JS.
Differential Revision: D119919582
Pulled By: vzaidman