monaco-editor
Version:
A browser based code editor
47 lines (44 loc) • 1.99 kB
JavaScript
import { BugIndicatingError } from '../../errors.js';
import { strictEquals } from '../../equals.js';
import '../../event.js';
import '../../lifecycle.js';
import { subtransaction } from '../transaction.js';
import { DebugNameData } from '../debugName.js';
import { DerivedWithSetter } from '../observables/derivedImpl.js';
import { DebugLocation } from '../debugLocation.js';
/*---------------------------------------------------------------------------------------------
* Copyright (c) Microsoft Corporation. All rights reserved.
* Licensed under the MIT License. See License.txt in the project root for license information.
*--------------------------------------------------------------------------------------------*/
/**
* Creates an observable value that is based on values and changes from other observables.
* Additionally, a reducer can report how that state changed.
*/
function observableReducerSettable(owner, options) {
let prevValue = undefined;
let hasValue = false;
const d = new DerivedWithSetter(new DebugNameData(owner, undefined, options.update), (reader, changeSummary) => {
if (!hasValue) {
prevValue = options.initial instanceof Function ? options.initial() : options.initial;
hasValue = true;
}
const newValue = options.update(reader, prevValue, changeSummary);
prevValue = newValue;
return newValue;
}, options.changeTracker, () => {
if (hasValue) {
options.disposeFinal?.(prevValue);
hasValue = false;
}
}, options.equalityComparer ?? strictEquals, (value, tx, change) => {
if (!hasValue) {
throw new BugIndicatingError('Can only set when there is a listener! This is to prevent leaks.');
}
subtransaction(tx, tx => {
prevValue = value;
d.setValue(value, tx, change);
});
}, DebugLocation.ofCaller());
return d;
}
export { observableReducerSettable };