target in tsconfig doesn't affect esbuild's runtime library

[mengxinssfd]

I found that after building the code, there is an extra __spreadValues function, which is written inside var prop in b ||= {}

var __spreadValues = (a, b) => {
  for (var prop in b ||= {})
    if (__hasOwnProp.call(b, prop))
      __defNormalProp(a, prop, b[prop]);
  if (__getOwnPropSymbols)
    for (var prop of __getOwnPropSymbols(b)) {
      if (__propIsEnum.call(b, prop))
        __defNormalProp(a, prop, b[prop]);
    }
  return a;
};

It's using the ECMAScript 2021 - (ES12) feature, when I set the target to a version before ES12, it doesn't work

[evanw]

Can you provide a self-contained code sample and esbuild configuration that will reproduce the problem?

[mengxinssfd]

Can you provide a self-contained code sample and esbuild configuration that will reproduce the problem?

You can look at this repository https://github.com/mengxinssfd/esbuild-isuue--2628.

Sorry, what I said earlier was not correct. esbuild.build({target:'ES2017'}) is useful.

It is accurate to use the target inside tsconfig.json without specifying target:'ES version'.

[nettybun]

@evanw I ran into this just now, the issue is that ||= is used despite the tsconfig target asking for ES6. Here's a repro:

$ echo 'var a = { a:1 }; export default { b:2, ...a }' | npx esbuild --loader=ts --tsconfig-raw='{"compilerOptions": { "target": "es6" }}'

var __defProp = Object.defineProperty;
var __getOwnPropSymbols = Object.getOwnPropertySymbols;
var __hasOwnProp = Object.prototype.hasOwnProperty;
var __propIsEnum = Object.prototype.propertyIsEnumerable;
var __defNormalProp = (obj, key, value) => key in obj ? __defProp(obj, key, { enumerable: true, configurable: true, writable: true, value }) : obj[key] = value;
var __spreadValues = (a2, b) => {
  for (var prop in b ||= {})
    if (__hasOwnProp.call(b, prop))
      __defNormalProp(a2, prop, b[prop]);
  if (__getOwnPropSymbols)
    for (var prop of __getOwnPropSymbols(b)) {
      if (__propIsEnum.call(b, prop))
        __defNormalProp(a2, prop, b[prop]);
    }
  return a2;
};
var a = { a: 1 };
export default __spreadValues({ b: 2 }, a);

Here's the docs that says tsconfig target will be respected: https://esbuild.github.io/content-types/#tsconfig-json

Using --target=es6 will correctly transform ||=

$ echo 'var a = { a:1 }; export default { b:2, ...a }' | npx esbuild --loader=ts --tsconfig-raw='{"compilerOptions": { "target": "es6" }}' --target=es6

...
for (var prop in b || (b = {}))
...

[evanw]

FYI I'm changing this so target in tsconfig.json doesn't affect any file, including esbuild's runtime library. You'll now have to use esbuild's --target=es2021 setting for this.