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George Zahariev
d992ae0448
Summary:
Codemod `Object.assign` with object literal first argument (e.g. `Object.assign({}, foo)`) to object spread.
This adds several suppressions for exposed errors. The codemod produces errors as `Object.assign` is more unsafe than object spread. For example, `Object.assign` doesn't handle indexers, nor does it handle inexact objects properly, and when the (currently unsealed) empty object is supplied as the first argument, it also leads to unsafe behaviour:
https://flow.org/try/#0FAehAIGJwSQOwCYFMAeSBOBnYyDGAbAQ3SXADdjwBbQgBwC5wBvAbUwBd0BLOAcwF1GHbnwC+AbmDAAFAHkARgCskudgDpCmTF15xpTQowCMogDTU6ASkbyA9rfxJCcS+PBhwAfm8ymwcAGG4Eam-gFqETS0oaKu7hAAyrQkhAjgGOi2WOCa6Si0KuxICFIe0PCohKo5AGZF6HlV7DgqRCTklDyVqowGQpw8vOYRahJSCsqqGlo6en3gAEQAFlwL5vLGZuBdKE1xHjtN4Li2AK74abZkGVzI4AAG8vfgUvphOYzLq6EB4BvBP3CEUOqhi+0SyScaQyWUwOThqAKqmKpQg0AAqnBME5HGkalwsOwcuheDIJoVptpdPotvMTNZmDV7Iw4KcqPIMLE3B5vN4gA
The codemod is safe to do, despite some Flow errors, as `Object.assign` and object spread are equivalent at runtime, with the exception that `Object.assign` triggers setters on the target object. However the codemod [does not run](https://github.com/eslint/eslint/blob/938dbdd6c310784cc8a7329efaeb0e34321b9e1f/lib/rules/prefer-object-spread.js#L283-L285) if the first argument (object literal) has getters/setters, so we are fine.
```
ag -l 'Object.assign\(' | xargs ag -l 'flow' | xargs js1 lint --rule '{"prefer-object-spread":2}' --fix
```
Some manual fixes
```
arc f
```
Reviewed By: SamChou19815
Differential Revision: D36023786
fbshipit-source-id: b682562e670410acf4175ba59ab285c7bdcfe052