add throwIfAborted and rejectIfAborted utilities to simplify AbortSignal handling

packages/backend/src/misc/throw-if-aborted.ts

@@ -0,0 +1,20 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { AbortedError } from '@/misc/errors/AbortedError.js';
+
+export function throwIfAborted(signal: AbortSignal): void {
+	if (signal.aborted) {
+		throw new AbortedError(signal);
+	}
+}
+
+export function rejectIfAborted(signal: AbortSignal): Promise<void> {
+	if (signal.aborted) {
+		return Promise.reject(new AbortedError(signal));
+	} else {
+		return Promise.resolve();
+	}
+}