admin: associate inline field errors with their inputs

network assignment rows, activity filters, and the settings password pair now mark the offending input with aria-invalid and point it at the error text with aria-describedby. the prefix validator returns the row and field it is about, and any row mutation clears a message that named a position. settings numeric fields carry aria-invalid on an unparseable value.

admin/src/features/clients/ClientsPage.test.tsx

@@ -2,6 +2,20 @@ import { fireEvent, render, screen, waitFor, within } from "@testing-library/rea
 import { ClientName, type ClientNames } from "./clientNames";
 import { BASE, MANAGED_FILE, NEVER, renderClientsPage, setConfigStatus } from "./testFixtures";
 
+/** The text of the elements an input points at with `aria-describedby`. */
+function describedText(input: HTMLElement): string {
+	const ids = input.getAttribute("aria-describedby");
+	if (ids === null) throw new Error("input has no aria-describedby");
+	return ids
+		.split(/\s+/)
+		.map((id) => {
+			const node = document.getElementById(id);
+			if (node === null) throw new Error(`aria-describedby names missing element ${id}`);
+			return node.textContent ?? "";
+		})
+		.join(" ");
+}
+
 function clientRow(ip: string): HTMLElement {
 	const row = screen.getByText(ip).closest("tr");
 	if (row === null) throw new Error(`no client row for ${ip}`);
@@ -315,7 +329,9 @@ describe.each([
 		fireEvent.click(confirm);
 		await waitFor(() =>
 			expect(
-				fetchMock.mock.calls.filter(([input, init]) => init?.method === "DELETE" && String(input).endsWith("/1")),
+				fetchMock.mock.calls.filter(
+					([input, init]) => init?.method === "DELETE" && String(input).endsWith("/1"),
+				),
 			).toHaveLength(1),
 		);
 	});
@@ -357,3 +373,66 @@ test("a pending config status holds the same line as a failed one (R3-4)", async
 	const observed = clientRow("192.168.1.11");
 	expect((within(observed).getByRole("button", { name: "Delete" }) as HTMLButtonElement).disabled).toBe(false);
 });
+
+test("a save-time problem marks the input it is about and describes it", async () => {
+	await renderClientsPage();
+
+	const range = (await screen.findByLabelText("Range 1")) as HTMLInputElement;
+	fireEvent.change(range, { target: { value: "" } });
+	fireEvent.click(screen.getByRole("button", { name: "Save assignments" }));
+
+	expect(range.getAttribute("aria-invalid")).toBe("true");
+	expect(describedText(range)).toBe("Row 1: prefix is required.");
+
+	// Only the offending input is marked; the priority beside it is untouched.
+	const priority = screen.getByLabelText("Priority for range 1");
+	expect(priority.getAttribute("aria-invalid")).toBeNull();
+	expect(priority.getAttribute("aria-describedby")).toBeNull();
+
+	fireEvent.change(range, { target: { value: "10.0.0.0/8" } });
+	fireEvent.change(screen.getByLabelText("Priority for range 1"), { target: { value: "abc" } });
+	fireEvent.click(screen.getByRole("button", { name: "Save assignments" }));
+
+	expect(range.getAttribute("aria-invalid")).toBeNull();
+	expect(describedText(screen.getByLabelText("Priority for range 1"))).toBe(
+		"Row 1: priority must be a whole number.",
+	);
+});
+
+test("removing a row drops the message rather than moving it to another input", async () => {
+	await renderClientsPage();
+
+	// Row 1 is the offending one, so removing it is what would slide the stale
+	// index onto row 2 — an input that validated cleanly.
+	const range = (await screen.findByLabelText("Range 1")) as HTMLInputElement;
+	fireEvent.change(range, { target: { value: "" } });
+	fireEvent.click(screen.getByRole("button", { name: "Add range" }));
+	fireEvent.change(screen.getByLabelText("Range 2"), { target: { value: "10.0.0.0/8" } });
+	fireEvent.click(screen.getByRole("button", { name: "Save assignments" }));
+
+	expect(range.getAttribute("aria-invalid")).toBe("true");
+	expect(describedText(range)).toBe("Row 1: prefix is required.");
+
+	const section = assignmentsSection();
+	fireEvent.click(within(section).getAllByRole("button", { name: "Remove" })[0] as HTMLButtonElement);
+
+	const survivor = screen.getByLabelText("Range 1") as HTMLInputElement;
+	expect(survivor.value).toBe("10.0.0.0/8");
+	expect(survivor.getAttribute("aria-invalid")).toBeNull();
+	expect(survivor.getAttribute("aria-describedby")).toBeNull();
+	expect(within(section).queryByRole("alert")).toBeNull();
+	expect(screen.queryByLabelText("Range 2")).toBeNull();
+});
+
+test("editing a row clears the message it was about", async () => {
+	await renderClientsPage();
+
+	const range = (await screen.findByLabelText("Range 1")) as HTMLInputElement;
+	fireEvent.change(range, { target: { value: "" } });
+	fireEvent.click(screen.getByRole("button", { name: "Save assignments" }));
+	expect(range.getAttribute("aria-invalid")).toBe("true");
+
+	fireEvent.change(range, { target: { value: "10.0.0.0/8" } });
+	expect(range.getAttribute("aria-invalid")).toBeNull();
+	expect(within(assignmentsSection()).queryByRole("alert")).toBeNull();
+});