feat: map 422 field errors for playground forms

surfsense_web/lib/playground/field-errors.test.ts

@@ -0,0 +1,34 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { AppError } from "@/lib/error";
+import { fieldErrorsFromError } from "./field-errors";
+
+// Run with: pnpm exec tsx --test lib/playground/field-errors.test.ts
+
+function validationError(fields: { loc: string[]; msg: string }[]): AppError {
+	const error = new AppError("Validation failed", 422, "Unprocessable Entity", "VALIDATION_ERROR");
+	error.fields = fields;
+	return error;
+}
+
+test("maps a body field failure to its top-level field name", () => {
+	const error = validationError([
+		{ loc: ["body", "startUrls", "0"], msg: "must be a valid http(s) URL" },
+	]);
+	assert.deepEqual(fieldErrorsFromError(error), {
+		startUrls: "must be a valid http(s) URL",
+	});
+});
+
+test("keeps the first failure per field", () => {
+	const error = validationError([
+		{ loc: ["body", "urls", "0"], msg: "first" },
+		{ loc: ["body", "urls", "3"], msg: "second" },
+	]);
+	assert.deepEqual(fieldErrorsFromError(error), { urls: "first" });
+});
+
+test("returns nothing for non-AppError or errors without fields", () => {
+	assert.deepEqual(fieldErrorsFromError(new Error("boom")), {});
+	assert.deepEqual(fieldErrorsFromError(new AppError("no fields", 500)), {});
+});

surfsense_web/lib/playground/field-errors.ts

@@ -0,0 +1,18 @@
+import { AppError } from "@/lib/error";
+
+/** Map a 422 response's field failures to ``{ fieldName: message }`` for the form. */
+export function fieldErrorsFromError(error: unknown): Record<string, string> {
+	if (!(error instanceof AppError) || !error.fields) return {};
+	const errors: Record<string, string> = {};
+	for (const { loc, msg } of error.fields) {
+		const name = topLevelField(loc);
+		if (name && !errors[name]) errors[name] = msg;
+	}
+	return errors;
+}
+
+/** The input field a location path points at, dropping the ``body`` request root. */
+function topLevelField(loc: string[]): string | undefined {
+	const path = loc[0] === "body" ? loc.slice(1) : loc;
+	return path[0];
+}