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avoid to change when meet __proto__ #956
Description
Bug report or Feature request? Bug report
Version (complete output of terser -V or specific git commit) 5.6.0
Complete CLI command or minify() options used
terser input
// sample 1:
const o = {};
o.p = 1;
o.__proto__ = { set q (v) {} };
o.q = 2;
console.log(o);
// sample 2:
const x = { __proto__: { set p (v) {} } };
x.p = 1;
console.log(x);terser output or error
// sample 1:
const o = { p: 1, __proto__: { set q (v) {} }, q: 2 };
console.log(o);
// sample 2:
const x = { __proto__: { set p (v) {} }, p: 1 };
console.log(x);Expected result
// sample 1:
const o = { p: 1 };
o.__proto__ = { set q (v) {} };
o.q = 2;
console.log(o);
// sample 2:
const x = { __proto__: { set p (v) {} } };
x.p = 1;
console.log(x);
Activity
fabiosantoscode commentedon Apr 3, 2021
Hey there! I can't reproduce sample 1. What were the options you used?
LongTengDao commentedon Apr 4, 2021
I used default options, so I didn't write it in the issue.
It's strange, because when I test, the sample 1 happens... And now it not happen...
Let's ignore sample 1, until I figure out why...
evanw commentedon Apr 22, 2021
I'm currently working through this for esbuild in evanw/esbuild#1166. I believe you can set missing properties to
undefinedwhen__proto__: nullis present (so{__proto__: null}.ais alwaysundefined) but not with['__proto__']: null. You also need to be careful to preserve{__proto__: null}.__proto__ === undefined. JS is so messy.fabiosantoscode commentedon Apr 23, 2021
Thanks for the input @evanw. I've read through this esbuild issue (it mentioned #980) for more insight. I don't know how widespread
__proto__: nullis though, so I don't know if it's worth the extra complexity. Maybe it's more worth it to optimize Map and Set (maybe an unsafe_collections option), since their behaviour is way more linear!