Object spread is supported in Node >= 8.3 but polyfilled by esbuild

[tinovyatkin]

Object spread syntax is supported in Node starting 8.3 (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax#browser_compatibility) but esbuild currently outputs __spreadValues polyfill for anything higher than --target=node8.3.0 (I've checked with node16 also) - see repl

Compare the output with --target=es2018 that is what we should get for the Node target.

[evanw]

This is deliberate. V8's native implementation of object spread is being avoided because it has performance issues. See also: #951, #1365, #1583.

[tinovyatkin]

Wow. Number of times this issue was raised probably is the best indicator that this deliberate decision are confusing and misleading for users.

esbuild is a great tool (thank you!) that have 3 documented functions: transpiling, bundling and minifying. All of them are optional. But now it happens that there is a speed optimizer also, that even in case when user provides precise target can make deliberate decision to change syntax from supported by the target. And not for bug fixing, etc, but for a performance optimization?

I understand you don't want to create a lot of switches of that features, but can we, similar to mangle/minify, have an option to switch off performance optimizations?

There are lot of similar performance optimization exists (almost with every iterable), why object spread was chosen as the only optimization target? Or there are other language syntax constructions that are transforming for performance reasons?