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fix(frontend): harden modal focus management #594

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fix(frontend): harden modal focus management #594

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29 changes: 23 additions & 6 deletions frontend/components/ui/Modal.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,9 @@ export interface ModalProps {
*/
title?: React.ReactNode;

/** Accessible name used when the dialog has no visible title. */
ariaLabel?: string;

/**
* Optional description text displayed under the title.
*/
Expand Down Expand Up @@ -52,6 +55,7 @@ export function Modal({
isOpen,
onClose,
title,
ariaLabel,
description,
children,
footer,
Expand All @@ -74,14 +78,26 @@ export function Modal({

// Accessible Focus Trap
if (e.key === "Tab" && modalRef.current) {
const focusableElements = modalRef.current.querySelectorAll<HTMLElement>(
'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
);
if (!focusableElements.length) return;

const focusableElements = Array.from(
modalRef.current.querySelectorAll<HTMLElement>(
'button:not([disabled]), [href]:not([aria-disabled="true"]), input:not([type="hidden"]):not([disabled]), select:not([disabled]), textarea:not([disabled]), [tabindex]:not([tabindex="-1"]):not([aria-disabled="true"])'
)
).filter((element) => !element.closest('[hidden], [aria-hidden="true"]'));
const firstElement = focusableElements[0];
const lastElement = focusableElements[focusableElements.length - 1];

if (!firstElement || !lastElement) {
e.preventDefault();
modalRef.current.focus();
return;
}

if (!modalRef.current.contains(document.activeElement)) {
e.preventDefault();
(e.shiftKey ? lastElement : firstElement).focus();
return;
}

if (e.shiftKey) {
if (document.activeElement === firstElement) {
e.preventDefault();
Expand All @@ -108,7 +124,7 @@ export function Modal({
requestAnimationFrame(() => {
if (modalRef.current) {
const focusable = modalRef.current.querySelector<HTMLElement>(
'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
'button:not([disabled]), [href]:not([aria-disabled="true"]), input:not([type="hidden"]):not([disabled]), select:not([disabled]), textarea:not([disabled]), [tabindex]:not([tabindex="-1"]):not([aria-disabled="true"])'
);
focusable ? focusable.focus() : modalRef.current.focus();
}
Expand Down Expand Up @@ -146,6 +162,7 @@ export function Modal({
role="dialog"
aria-modal="true"
aria-labelledby={title ? titleId : undefined}
aria-label={!title ? ariaLabel ?? "Dialog" : undefined}
aria-describedby={description ? descId : undefined}
tabIndex={-1}
className={`relative z-10 w-full ${maxWidth} rounded-2xl border border-gray-100 bg-white p-6 shadow-2xl transition-all outline-none dark:border-gray-700 dark:bg-gray-800`}
Expand Down
26 changes: 26 additions & 0 deletions frontend/components/ui/ui.test.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,32 @@ describe("UI Primitives", () => {
});

describe("Modal", () => {
it("names an untitled dialog and keeps keyboard focus inside", async () => {
render(
<>
<button type="button">Outside action</button>
<Modal isOpen onClose={jest.fn()} ariaLabel="Authentication dialog">
<button type="button">Continue</button>
</Modal>
</>
);

const dialog = screen.getByRole("dialog", { name: "Authentication dialog" });
const closeButton = screen.getByRole("button", { name: "Close dialog" });
const continueButton = screen.getByRole("button", { name: "Continue" });
expect(dialog).toHaveAttribute("aria-modal", "true");
await waitFor(() => expect(closeButton).toHaveFocus());

fireEvent.keyDown(closeButton, { key: "Tab", shiftKey: true });
expect(continueButton).toHaveFocus();
fireEvent.keyDown(continueButton, { key: "Tab" });
expect(closeButton).toHaveFocus();

screen.getByRole("button", { name: "Outside action" }).focus();
fireEvent.keyDown(screen.getByRole("button", { name: "Outside action" }), { key: "Tab" });
expect(closeButton).toHaveFocus();
});

it("restores focus to the trigger after closing", () => {
function ModalHarness() {
const [open, setOpen] = React.useState(false);
Expand Down