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Test Info: Warnings
- This test has a WPT meta file that expects 7 subtest issues.
- This WPT test may be referenced by the following Test IDs:
- /dom/observable/tentative/observable-reduce.any.html - WPT Dashboard Interop Dashboard
- /dom/observable/tentative/observable-reduce.any.worker.html - WPT Dashboard Interop Dashboard
promise_test(async t => {
const source = new Observable(subscriber => {
subscriber.next(1);
subscriber.next(2);
subscriber.next(3);
t.step_timeout(() => subscriber.complete(), 0);
});
const reducerArguments = [];
const promiseToResult = source.reduce((acc, value, index) => {
reducerArguments.push([acc, value, index]);
return acc + value;
}, 0);
// The reducer should be called immediately when the source emits a value.
assert_equals(reducerArguments.length, 3);
assert_array_equals(reducerArguments[0], [0, 1, 0]);
assert_array_equals(reducerArguments[1], [1, 2, 1]);
assert_array_equals(reducerArguments[2], [3, 3, 2]);
const result = await promiseToResult;
assert_equals(result, 6);
}, "reduce(): Reduces the values of the Observable, starting with the " +
"initial seed value");
promise_test(async () => {
let error = new Error('from the source');
const source = new Observable(subscriber => {
subscriber.next(1);
subscriber.error(error);
});
let thrownError = null;
try {
await source.reduce((acc, value) => acc + value, 0);
} catch (error) {
thrownError = error;
}
assert_equals(thrownError, error);
}, "reduce(): Rejects if the source observable emits an error");
promise_test(async t => {
const source = new Observable(subscriber => {
subscriber.next(1);
subscriber.next(2);
subscriber.next(3);
t.step_timeout(() => subscriber.complete(), 0);
});
const reducerArguments = [];
const promiseToResult = source.reduce((acc, value, index) => {
reducerArguments.push([acc, value, index]);
return acc + value;
});
// The reducer should be called immediately when the source emits a value.
assert_equals(reducerArguments.length, 2);
assert_array_equals(reducerArguments[0], [1, 2, 1]);
assert_array_equals(reducerArguments[1], [3, 3, 2]);
const result = await promiseToResult;
assert_equals(result, 6);
}, "reduce(): Seeds with the first value of the source, if no initial value " +
"is provided");
promise_test(async () => {
const logs = [];
const source = new Observable(subscriber => {
subscriber.addTeardown(() => logs.push('teardown'));
logs.push('next 1');
subscriber.next(1);
logs.push('next 2');
subscriber.next(2);
logs.push('try to next 3');
subscriber.next(3);
logs.push('try to complete');
subscriber.complete();
});
const error = new Error('from the reducer');
let thrownError = null;
try {
await source.reduce((acc, value) => {
if (value === 2) {
logs.push('throw error');
throw error;
}
return acc + value;
}, 0);
} catch (error) {
thrownError = error;
}
assert_equals(thrownError, error);
assert_array_equals(logs, [
'next 1',
'next 2',
'throw error',
'teardown',
'try to next 3',
'try to complete',
]);
}, "reduce(): Errors thrown in reducer reject the promise and abort the source");
promise_test(async () => {
const source = new Observable(subscriber => {
subscriber.complete();
});
const result = await source.reduce(() => 'reduced', 'seed');
assert_equals(result, 'seed');
}, "reduce(): When source is empty, promise resolves with initial value");
promise_test(async () => {
// This tests behavior that is analogous to `[].reduce(() => 'reduced')`,
// which throws a TypeError.
const source = new Observable(subscriber => {
subscriber.complete();
});
let thrownError = null;
try {
await source.reduce(() => 'reduced');
} catch (error) {
thrownError = error;
}
assert_true(thrownError instanceof TypeError);
}, "reduce(): When source is empty, AND no seed value is provided, the " +
"promise rejects with a TypeError");
promise_test(async t => {
let tornDown = false;
const source = new Observable((subscriber) => {
subscriber.addTeardown(() => {
tornDown = true;
});
// Waits forever.
});
const abortController = new AbortController();
t.step_timeout(() => {
abortController.abort();
assert_true(tornDown);
}, 0);
let thrownError = null;
try {
await source.reduce(() => 'reduced', 'seed', { signal: abortController.signal });
} catch (error) {
thrownError = error;
}
assert_true(thrownError instanceof DOMException);
assert_equals(thrownError.name, 'AbortError');
}, "reduce(): Reject with an AbortError if the subscription is aborted " +
"before the source completes");