src/vs/base/common/observableImpl/utils.ts/FromEventObservable/handleEvent
class FromEventObservable:	private readonly handleEvent = (args: TArgs | undefined) => {
		const newValue = this.getValue(args);

		const didChange = this.value !== newValue;

		getLogger()?.handleFromEventObservableTriggered(this, { oldValue: this.value, newValue, change: undefined, didChange });

		if (didChange) {
			this.value = newValue;

			if (this.hasValue) {
				transaction(
					(tx) => {
						for (const o of this.observers) {
							tx.updateObserver(o, this);
							o.handleChange(this, undefined);
						}
					},
					() => {
						const name = this.getDebugName();
						return 'Event fired' + (name ? `: ${name}` : '');
					}
				);
			}
			this.hasValue = true;
		}
	};