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add defer/stream support for subscriptions (#7)
# Conflicts: # src/subscription/subscribe.ts
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src/subscription/__tests__/flattenAsyncIterator-test.ts
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import { expect } from 'chai'; | ||
import { describe, it } from 'mocha'; | ||
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import { flattenAsyncIterator } from '../flattenAsyncIterator'; | ||
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describe('flattenAsyncIterator', () => { | ||
it('does not modify an already flat async generator', async () => { | ||
async function* source() { | ||
yield await Promise.resolve(1); | ||
yield await Promise.resolve(2); | ||
yield await Promise.resolve(3); | ||
} | ||
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const result = flattenAsyncIterator(source()); | ||
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expect(await result.next()).to.deep.equal({ value: 1, done: false }); | ||
expect(await result.next()).to.deep.equal({ value: 2, done: false }); | ||
expect(await result.next()).to.deep.equal({ value: 3, done: false }); | ||
expect(await result.next()).to.deep.equal({ | ||
value: undefined, | ||
done: true, | ||
}); | ||
}); | ||
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it('does not modify an already flat async iterator', async () => { | ||
const items = [1, 2, 3]; | ||
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const iterator: any = { | ||
[Symbol.asyncIterator]() { | ||
return this; | ||
}, | ||
next() { | ||
return Promise.resolve({ | ||
done: items.length === 0, | ||
value: items.shift(), | ||
}); | ||
}, | ||
}; | ||
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const result = flattenAsyncIterator(iterator); | ||
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expect(await result.next()).to.deep.equal({ value: 1, done: false }); | ||
expect(await result.next()).to.deep.equal({ value: 2, done: false }); | ||
expect(await result.next()).to.deep.equal({ value: 3, done: false }); | ||
expect(await result.next()).to.deep.equal({ | ||
value: undefined, | ||
done: true, | ||
}); | ||
}); | ||
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it('flatten nested async generators', async () => { | ||
async function* source() { | ||
yield await Promise.resolve(1); | ||
yield await Promise.resolve(2); | ||
yield await Promise.resolve( | ||
(async function* nested(): AsyncGenerator<number, void, void> { | ||
yield await Promise.resolve(2.1); | ||
yield await Promise.resolve(2.2); | ||
})(), | ||
); | ||
yield await Promise.resolve(3); | ||
} | ||
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const doubles = flattenAsyncIterator(source()); | ||
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const result = []; | ||
for await (const x of doubles) { | ||
result.push(x); | ||
} | ||
expect(result).to.deep.equal([1, 2, 2.1, 2.2, 3]); | ||
}); | ||
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it('allows returning early from a nested async generator', async () => { | ||
async function* source() { | ||
yield await Promise.resolve(1); | ||
yield await Promise.resolve(2); | ||
yield await Promise.resolve( | ||
(async function* nested(): AsyncGenerator<number, void, void> { | ||
yield await Promise.resolve(2.1); | ||
// istanbul ignore next (Shouldn't be reached) | ||
yield await Promise.resolve(2.2); | ||
})(), | ||
); | ||
// istanbul ignore next (Shouldn't be reached) | ||
yield await Promise.resolve(3); | ||
} | ||
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const doubles = flattenAsyncIterator(source()); | ||
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expect(await doubles.next()).to.deep.equal({ value: 1, done: false }); | ||
expect(await doubles.next()).to.deep.equal({ value: 2, done: false }); | ||
expect(await doubles.next()).to.deep.equal({ value: 2.1, done: false }); | ||
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// Early return | ||
expect(await doubles.return()).to.deep.equal({ | ||
value: undefined, | ||
done: true, | ||
}); | ||
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// Subsequent next calls | ||
expect(await doubles.next()).to.deep.equal({ | ||
value: undefined, | ||
done: true, | ||
}); | ||
expect(await doubles.next()).to.deep.equal({ | ||
value: undefined, | ||
done: true, | ||
}); | ||
}); | ||
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it('allows throwing errors from a nested async generator', async () => { | ||
async function* source() { | ||
yield await Promise.resolve(1); | ||
yield await Promise.resolve(2); | ||
yield await Promise.resolve( | ||
(async function* nested(): AsyncGenerator<number, void, void> { | ||
yield await Promise.resolve(2.1); | ||
// istanbul ignore next (Shouldn't be reached) | ||
yield await Promise.resolve(2.2); | ||
})(), | ||
); | ||
// istanbul ignore next (Shouldn't be reached) | ||
yield await Promise.resolve(3); | ||
} | ||
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const doubles = flattenAsyncIterator(source()); | ||
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expect(await doubles.next()).to.deep.equal({ value: 1, done: false }); | ||
expect(await doubles.next()).to.deep.equal({ value: 2, done: false }); | ||
expect(await doubles.next()).to.deep.equal({ value: 2.1, done: false }); | ||
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// Throw error | ||
let caughtError; | ||
try { | ||
await doubles.throw('ouch'); | ||
} catch (e) { | ||
caughtError = e; | ||
} | ||
expect(caughtError).to.equal('ouch'); | ||
}); | ||
}); |
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import { isAsyncIterable } from '../jsutils/isAsyncIterable'; | ||
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type AsyncIterableOrGenerator<T> = | ||
| AsyncGenerator<T, void, void> | ||
| AsyncIterable<T>; | ||
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/** | ||
* Given an AsyncIterable that could potentially yield other async iterators, | ||
* flatten all yielded results into a single AsyncIterable | ||
*/ | ||
export function flattenAsyncIterator<T, AT>( | ||
iterable: AsyncIterableOrGenerator<T | AsyncIterableOrGenerator<AT>>, | ||
): AsyncGenerator<T | AT, void, void> { | ||
const iteratorMethod = iterable[Symbol.asyncIterator]; | ||
const iterator: any = iteratorMethod.call(iterable); | ||
let iteratorStack: Array<AsyncIterator<T>> = [iterator]; | ||
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async function next(): Promise<IteratorResult<T | AT, void>> { | ||
const currentIterator = iteratorStack[0]; | ||
if (!currentIterator) { | ||
return { value: undefined, done: true }; | ||
} | ||
const result = await currentIterator.next(); | ||
if (result.done) { | ||
iteratorStack.shift(); | ||
return next(); | ||
} else if (isAsyncIterable(result.value)) { | ||
const childIterator = result.value[ | ||
Symbol.asyncIterator | ||
]() as AsyncIterator<T>; | ||
iteratorStack.unshift(childIterator); | ||
return next(); | ||
} | ||
return result; | ||
} | ||
return { | ||
next, | ||
return() { | ||
iteratorStack = []; | ||
return iterator.return(); | ||
}, | ||
throw(error?: unknown): Promise<IteratorResult<T | AT>> { | ||
iteratorStack = []; | ||
return iterator.throw(error); | ||
}, | ||
[Symbol.asyncIterator]() { | ||
return this; | ||
}, | ||
}; | ||
} |
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