38 lines
1.2 KiB
TypeScript
38 lines
1.2 KiB
TypeScript
/*
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Copyright 2023 New Vector Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { Observable, defer, finalize, tap } from "rxjs";
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const nothing = Symbol("nothing");
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/**
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* RxJS operator that invokes a callback when the Observable is finalized,
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* passing the most recently emitted value. If no value was emitted, the
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* callback will not be invoked.
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*/
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export function finalizeValue<T>(callback: (finalValue: T) => void) {
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return (source: Observable<T>): Observable<T> =>
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defer(() => {
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let finalValue: T | typeof nothing = nothing;
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return source.pipe(
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tap((value) => (finalValue = value)),
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finalize(() => {
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if (finalValue !== nothing) callback(finalValue);
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}),
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);
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});
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}
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