add renderInlineError to serialize errors in a consistent way

packages/backend/src/misc/render-inline-error.ts

@@ -0,0 +1,35 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { IdentifiableError } from '@/misc/identifiable-error.js';
+import { StatusError } from '@/misc/status-error.js';
+
+export function renderInlineError(err: unknown): string {
+	if (err instanceof IdentifiableError) {
+		if (err.message) {
+			return `${err.name} ${err.id}: ${err.message}`;
+		} else {
+			return `${err.name} ${err.id}`;
+		}
+	}
+
+	if (err instanceof StatusError) {
+		if (err.message) {
+			return `${err.name} ${err.statusCode}: ${err.message}`;
+		} else {
+			return `${err.name} ${err.statusCode}`;
+		}
+	}
+
+	if (err instanceof Error) {
+		if (err.message) {
+			return `${err.name}: ${err.message}`;
+		} else {
+			return err.name;
+		}
+	}
+
+	return String(err);
+}