abortable-generator

Abortable AsyncGenerators using AbortControllers

Installation

``sh
npm i --save node-module-template
`

Usage

$3

`js
// esm
import abortable from 'abortable-generator
// commonjs
const abortable = require('abortable-generator').default
``

$3

There is a problem with AsyncGenerators where unsettled Promises can prevent them from finishing (and sometimes lead to memory leaks 😱)

`js
async function* getItems() {
try {
yield new Promise((resolve) => {})
} finally {
// this never happens
}
}

const items = getItems()

setTimeout(() => {
// some time later
items.return()
}, 100)
for await (let item of items) {
// this never happens
}
`

$3

Here's an example of how to abort "stuck" AsyncGenerators using abortable-generator

`js
import abortable from 'abortable-generators'

// wrap your AsyncGenerators with abortable and use raceAbort inside
const getItems = abortable(async function* (raceAbort) {
yield raceAbort(new Promise((resolve) => {}))
})
const items = getItems()

setTimeout(() => {
// some time later
// return will trigger an abort
items.return()
}, 100)
for await (let item of items) {
// generator didn't yield anything
}
`

$3

Here's an example of how to abort "stuck" AsyncGenerators using abortable-generator

`js
import abortable from 'abortable-generators'

// wrap your AsyncGenerators with abortable and use raceAbort inside
const getItems = abortable(async function* (raceAbort) {
try {
yield raceAbort(new Promise((resolve) => {}))
} catch (err) {
if (err.name === 'AbortError') {
// return will throw an AbortError, but it will be ignored even if rethrown here
return
}
throw err
} finally {
// done
}
})
const items = getItems()

setTimeout(() => {
// some time later
// return will throw an AbortError into the generator
items.return()
}, 100)
for await (let item of items) {
// generator didn't yield anything
}
`

$3

Here's an example of how to throw an error into a "stuck" AsyncGenerators using abortable-generator

`js
import abortable from 'abortable-generators'

// wrap your AsyncGenerators with abortable and use raceAbort inside
const getItems = abortable(async function* (raceAbort) {
try {
yield raceAbort(new Promise((resolve) => {}))
} catch (err) {
// [Error: boom]
throw err
} finally {
// done
}
})
const items = getItems()

setTimeout(() => {
// some time later
// return will throw this error into the generator
const err = new Error('boom')
items.throw(err)
}, 100)
for await (let item of items) {
// generator didn't yield anything
}
`

$3

Here's an example of how to abort "stuck" AsyncGenerators using abortable-generator

`js
import abortable from 'abortable-generators'

const controller = new AbortController()
const signal = controller.signal

// wrap your AsyncGenerators with abortable and use raceAbort inside
const getItems = abortable(async function* (raceAbort) {
try {
yield raceAbort(new Promise((resolve) => {}))
} catch (err) {
if (err.name === 'AbortError') {
// abort will throw an AbortError, but it will be ignored even if rethrown here
return
}
throw err
} finally {
// done
}
})

// abort-signal can also be used to abort abortable generators
const items = getItems(signal)

setTimeout(() => {
// some time later
controller.abort()
}, 100)
for await (let item of items) {
//
}
`

$3

Here's an example of how to abort AsyncGenerators that contain cancellable Promises (supporting AbortSignal)

`js
import abortable from 'abortable-generators'

const getItems = abortable(async function* (raceAbort) {
try {
yield raceAbort((signal) => fetch('https://codeshare.io', { signal }))
} catch (err) {
if (err.name === 'AbortError') {
// cancelled fetch will throw an AbortError, but it will be ignored even if rethrown here
return
}
throw err
} finally {
// done
}
})

const items = getItems()

setTimeout(() => {
// some time later
items.return()
}, 100)
for await (let item of items) {
//
}
`

$3

Here's an example of how to abort AsyncGenerators that contain cancellable Promises (supporting AbortSignal)

`js
import abortable from 'abortable-generators'

const controller = new AbortController()
const signal = controller.signal

const getMoreItems = abortable(async function* (raceAbort) {
try {
await raceAbort(timeoutPromise(100))
yield raceAbort((signal) => fetch('https://codeshare.io', { signal }))
} catch (err) {
if (err.name === 'AbortError') {
// aborted promises will throw an AbortError, but it will be ignored even if rethrown here
return
}
throw err
} finally {
// done
}
})
const getItems = abortable(async function* (raceAbort) {
let moreItems
try {
moreItems = await raceAbort(signal => getMoreItems(signal))
for await (let item in moreItems) {
yield item
}
await raceAbort(timeoutPromise(100))
yield raceAbort((signal) => fetch('https://codeshare.io', { signal }))
} catch (err) {
if (err.name === 'AbortError') {
// aborted promises will throw an AbortError, but it will be ignored even if rethrown here
return
}
// if you want to throw an error into a child generator you'll need to call throw manually
// if (err instanceof FooError) await moreItems.throw(err)
throw err
} finally {
// done
await moreItems?.return()
}
})
// this signal can also be used to abort the generator!
const items = getItems(signal)

setTimeout(() => {
// some time later
items.return()
}, 100)
for await (let item of items) {
//
}
``

License

MIT