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Merge pull request #7818 from apollographql/catch-asyncMap-next-excep…
…tions Improvements to asyncMap Observable utility function.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,136 @@ | ||
import { itAsync } from "../../testing"; | ||
import { Observable } from "../Observable"; | ||
import { asyncMap } from "../asyncMap"; | ||
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const wait = (delayMs: number) => | ||
new Promise<void>(resolve => setTimeout(resolve, delayMs)); | ||
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function make1234Observable() { | ||
return new Observable<number>(observer => { | ||
observer.next(1); | ||
observer.next(2); | ||
setTimeout(() => { | ||
observer.next(3); | ||
setTimeout(() => { | ||
observer.next(4); | ||
observer.complete(); | ||
}, 10); | ||
}, 10); | ||
}); | ||
} | ||
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function rejectExceptions<Args extends any[], Ret>( | ||
reject: (reason: any) => any, | ||
fn: (...args: Args) => Ret, | ||
) { | ||
return function () { | ||
try { | ||
return fn.apply(this, arguments); | ||
} catch (error) { | ||
reject(error); | ||
} | ||
} as typeof fn; | ||
} | ||
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describe("asyncMap", () => { | ||
itAsync("keeps normal results in order", (resolve, reject) => { | ||
const values: number[] = []; | ||
const mapped: number[] = []; | ||
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asyncMap(make1234Observable(), value => { | ||
values.push(value); | ||
// Make earlier results take longer than later results. | ||
const delay = 100 - value * 10; | ||
return wait(delay).then(() => value * 2); | ||
}).subscribe({ | ||
next(mappedValue) { | ||
mapped.push(mappedValue); | ||
}, | ||
error: reject, | ||
complete: rejectExceptions(reject, () => { | ||
expect(values).toEqual([1, 2, 3, 4]); | ||
expect(mapped).toEqual([2, 4, 6, 8]); | ||
resolve(); | ||
}), | ||
}); | ||
}); | ||
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itAsync("handles exceptions from mapping functions", (resolve, reject) => { | ||
const triples: number[] = []; | ||
asyncMap(make1234Observable(), num => { | ||
if (num === 3) throw new Error("expected"); | ||
return num * 3; | ||
}).subscribe({ | ||
next: rejectExceptions(reject, triple => { | ||
expect(triple).toBeLessThan(9); | ||
triples.push(triple); | ||
}), | ||
error: rejectExceptions(reject, error => { | ||
expect(error.message).toBe("expected"); | ||
expect(triples).toEqual([3, 6]); | ||
resolve(); | ||
}), | ||
}); | ||
}); | ||
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itAsync("handles rejected promises from mapping functions", (resolve, reject) => { | ||
const triples: number[] = []; | ||
asyncMap(make1234Observable(), num => { | ||
if (num === 3) return Promise.reject(new Error("expected")); | ||
return num * 3; | ||
}).subscribe({ | ||
next: rejectExceptions(reject, triple => { | ||
expect(triple).toBeLessThan(9); | ||
triples.push(triple); | ||
}), | ||
error: rejectExceptions(reject, error => { | ||
expect(error.message).toBe("expected"); | ||
expect(triples).toEqual([3, 6]); | ||
resolve(); | ||
}), | ||
}); | ||
}); | ||
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itAsync("handles async exceptions from mapping functions", (resolve, reject) => { | ||
const triples: number[] = []; | ||
asyncMap(make1234Observable(), num => wait(10).then(() => { | ||
if (num === 3) throw new Error("expected"); | ||
return num * 3; | ||
})).subscribe({ | ||
next: rejectExceptions(reject, triple => { | ||
expect(triple).toBeLessThan(9); | ||
triples.push(triple); | ||
}), | ||
error: rejectExceptions(reject, error => { | ||
expect(error.message).toBe("expected"); | ||
expect(triples).toEqual([3, 6]); | ||
resolve(); | ||
}), | ||
}); | ||
}); | ||
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itAsync("handles exceptions from next functions", (resolve, reject) => { | ||
const triples: number[] = []; | ||
asyncMap(make1234Observable(), num => { | ||
return num * 3; | ||
}).subscribe({ | ||
next(triple) { | ||
triples.push(triple); | ||
// Unfortunately this exception won't be caught by asyncMap, because | ||
// the Observable implementation wraps this next function with its own | ||
// try-catch. Uncomment the remaining lines to make this test more | ||
// meaningful, in the event that this behavior ever changes. | ||
// if (triple === 9) throw new Error("expected"); | ||
}, | ||
// error: rejectExceptions(reject, error => { | ||
// expect(error.message).toBe("expected"); | ||
// expect(triples).toEqual([3, 6, 9]); | ||
// resolve(); | ||
// }), | ||
complete: rejectExceptions(reject, () => { | ||
expect(triples).toEqual([3, 6, 9, 12]); | ||
resolve(); | ||
}), | ||
}); | ||
}); | ||
}); |
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