implement error types for disposal patterns

packages/backend/src/misc/errors/DisposeError.ts

@@ -0,0 +1,40 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+/**
+ * Common base class for DisposedError and DisposingError - please use only for catch() blocks.
+ */
+export abstract class DisposeError extends Error {
+	public readonly source: string | undefined;
+
+	protected constructor(opts?: { source?: string, message?: string }) {
+		super();
+		this.source = opts?.source;
+	}
+}
+
+/**
+ * Thrown when an attempt is made to use an object that has been disposed.
+ */
+export class DisposedError extends DisposeError {
+	constructor(opts?: { source?: string, message?: string }) {
+		super({
+			source: opts?.source,
+			message: opts?.message ?? `${opts?.source ?? 'Object'} has been disposed`,
+		});
+	}
+}
+
+/**
+ * Thrown when an object is use begins disposing.
+ */
+export class DisposingError extends DisposeError {
+	constructor(opts?: { source?: string, message?: string }) {
+		super({
+			source: opts?.source,
+			message: opts?.message ?? `${opts?.source ?? 'Object'} is being disposed`,
+		});
+	}
+}