evanw/esbuild
### [`v0.18.8`](https://togithub.com/evanw/esbuild/blob/HEAD/CHANGELOG.md#0188)
[Compare Source](https://togithub.com/evanw/esbuild/compare/v0.18.7...v0.18.8)
- Implement transforming `async` generator functions ([#2780](https://togithub.com/evanw/esbuild/issues/2780))
With this release, esbuild will now transform `async` generator functions into normal generator functions when the configured target environment doesn't support them. These functions behave similar to normal generator functions except that they use the `Symbol.asyncIterator` interface instead of the `Symbol.iterator` interface and the iteration methods return promises. Here's an example (helper functions are omitted):
```js
// Original code
async function* foo() {
yield Promise.resolve(1)
await new Promise(r => setTimeout(r, 100))
yield *[Promise.resolve(2)]
}
async function bar() {
for await (const x of foo()) {
console.log(x)
}
}
bar()
// New output (with --target=es6)
function foo() {
return __asyncGenerator(this, null, function* () {
yield Promise.resolve(1);
yield new __await(new Promise((r) => setTimeout(r, 100)));
yield* __yieldStar([Promise.resolve(2)]);
});
}
function bar() {
return __async(this, null, function* () {
try {
for (var iter = __forAwait(foo()), more, temp, error; more = !(temp = yield iter.next()).done; more = false) {
const x = temp.value;
console.log(x);
}
} catch (temp) {
error = [temp];
} finally {
try {
more && (temp = iter.return) && (yield temp.call(iter));
} finally {
if (error)
throw error[0];
}
}
});
}
bar();
```
This is an older feature that was added to JavaScript in ES2018 but I didn't implement the transformation then because it's a rarely-used feature. Note that esbuild already added support for transforming `for await` loops (the other part of the [asynchronous iteration proposal](https://togithub.com/tc39/proposal-async-iteration)) a year ago, so support for asynchronous iteration should now be complete.
I have never used this feature myself and code that uses this feature is hard to come by, so this transformation has not yet been tested on real-world code. If you do write code that uses this feature, please let me know if esbuild's `async` generator transformation doesn't work with your code.
Configuration
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â™» Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.
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This PR contains the following updates:
^0.18.7->^0.18.8Release Notes
evanw/esbuild
### [`v0.18.8`](https://togithub.com/evanw/esbuild/blob/HEAD/CHANGELOG.md#0188) [Compare Source](https://togithub.com/evanw/esbuild/compare/v0.18.7...v0.18.8) - Implement transforming `async` generator functions ([#2780](https://togithub.com/evanw/esbuild/issues/2780)) With this release, esbuild will now transform `async` generator functions into normal generator functions when the configured target environment doesn't support them. These functions behave similar to normal generator functions except that they use the `Symbol.asyncIterator` interface instead of the `Symbol.iterator` interface and the iteration methods return promises. Here's an example (helper functions are omitted): ```js // Original code async function* foo() { yield Promise.resolve(1) await new Promise(r => setTimeout(r, 100)) yield *[Promise.resolve(2)] } async function bar() { for await (const x of foo()) { console.log(x) } } bar() // New output (with --target=es6) function foo() { return __asyncGenerator(this, null, function* () { yield Promise.resolve(1); yield new __await(new Promise((r) => setTimeout(r, 100))); yield* __yieldStar([Promise.resolve(2)]); }); } function bar() { return __async(this, null, function* () { try { for (var iter = __forAwait(foo()), more, temp, error; more = !(temp = yield iter.next()).done; more = false) { const x = temp.value; console.log(x); } } catch (temp) { error = [temp]; } finally { try { more && (temp = iter.return) && (yield temp.call(iter)); } finally { if (error) throw error[0]; } } }); } bar(); ``` This is an older feature that was added to JavaScript in ES2018 but I didn't implement the transformation then because it's a rarely-used feature. Note that esbuild already added support for transforming `for await` loops (the other part of the [asynchronous iteration proposal](https://togithub.com/tc39/proposal-async-iteration)) a year ago, so support for asynchronous iteration should now be complete. I have never used this feature myself and code that uses this feature is hard to come by, so this transformation has not yet been tested on real-world code. If you do write code that uses this feature, please let me know if esbuild's `async` generator transformation doesn't work with your code.Configuration
📅 Schedule: Branch creation - "before 12pm on Sunday" (UTC), Automerge - At any time (no schedule defined).
🚦 Automerge: Enabled.
â™» Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.
🔕 Ignore: Close this PR and you won't be reminded about this update again.
This PR has been generated by Mend Renovate. View repository job log here.