Object.assign does not throw error when assign value to non-writable property.

[krave1986]

Environment

React Native Environment Info:
System:
OS: Windows 10
CPU: (4) x64 Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
Memory: 779.73 MB / 7.91 GB
Binaries:
npm: 6.4.1 - C:\Program Files\nodejs\npm.CMD
IDEs:
Android Studio: Version 3.2.0.0 AI-181.5540.7.32.5056338

Reproducible Demo

var target = Object.defineProperty({}, 'foo', {value: 1, writable: false});
Object.assign(target, {foo: 2});

Description

As illustrated on MDN doc and according to the behavior of latest version of chomr, when trying to assign a property which is non-writable in target from source to target, Object.assign should throw a TypeError like:

TypeError: Cannot assign to read only property 'foo' of object '#'

[lemiesz]

Hmm so I just tried this out, and although it does not throw an error in the React runtime.
It fails silently and the value of target.foo = 1.

What is interesting is that I would expect this to throw an error in the debugger regardless. Since all the debugger code is suppose to run in chrome

But maybe this is not a bug, as we are not using the chrome engine?

[Salakar]

@krave1986 thanks for raising this issue 🎉

I can confirm that since the new JSC landed on Android (RN v0.59.x) this now behaves correctly and throws a valid error.