Object spread incorrectly compiles getter

[dsehnal]

TypeScript Version: 2.9.1

Search Terms:
object spread getter

Code

const A = { a: 1 };
const X = { ...A, get x() { return this.a } };
const Y = { a: A.a, get x() { return this.a } };
console.log(X.x, Y.x)

Expected behavior:
1 1

Actual behavior:
undefined 1

The proposal says that get x() should not be called (section Getters on the Object Initializer).

Executing the code in Chrome (66) console produces the expected behavior.

Playground Link:
link

[Buslowicz]

Same issue happens with Babel. The solution would be to use Object.getOwnPropertyDescriptors() to get properties with their values and/or getters/setters, instead of just iterating over properties.

[SBhojani]

I just came across this one. Here's another piece of code to demonstrate the issue:

var x = {
 ...{}, 
 get r(){
 return Math.random();
 }
};
console.log(x.r);
console.log(x.r);
console.log(x.r);

In JS that logs 3 different random values. In TS, it logs a single random value thrice.

More at https://stackoverflow.com/questions/60861329/typescript-bug-this-difference-between-get-syntax-and-definepropertys-g .

[guitarino]

Just ran into this issue; it still exists in 4.9.4. Babel TypeScript works correctly.

[RyanCavanaugh]

Starting in 6.0 the minimum downlevel target will be ES6, which includes Object.assign, so there's no invocation of the spread helper anymore. Closing as moot.