test(e2e): cover configurable destinations; stop assuming a nav item

The assertions are about the navigation, not about the setting: "the
config was saved" is the plumbing, and #69 and #72 both shipped green
under specs that measured exactly that.

Four existing specs reached a view by clicking its nav item, which since
this change is not guaranteed to exist -- Autotag is hidden by default
and Downloads is absent without a download client -- so they timed out
waiting for a locator that will never resolve. `navigateTo` dispatches
the app's own `navigate` event, which is what every nav item, card and
detail view dispatches, so it is the mechanism rather than a test-only
door. Click the item when the nav is the subject.

Closes #25

e2e/specs/view-visibility.spec.ts

@@ -0,0 +1,116 @@
+import { test, expect, navigateTo } from '../support/fixtures.js';
+
+/**
+ * Which destinations the navigation offers (#25).
+ *
+ * Eleven sidebar entries is more than most libraries need, so they are
+ * individually toggleable from Settings, Autotag is off until asked for
+ * and Downloads is absent until there is a client to download with.
+ *
+ * **The assertions are about the navigation, not about the setting.**
+ * "The config was saved" is the plumbing, and the two most recent bugs
+ * in this area — #69 and #72 — both shipped green under specs that
+ * measured exactly that. What a person sees is whether the item is in
+ * the accessibility tree, and whether the view is still reachable when
+ * it is not.
+ *
+ * This runs against the seeded app, whose config is defaults and whose
+ * download client list is empty, so the initial state below is what a
+ * fresh install looks like.
+ */
+type Page = import('@playwright/test').Page;
+
+const navItem = (page: Page, label: string) =>
+  page.getByRole('button', { name: label, exact: true });
+
+/** The Navigation section's checkbox for a destination. */
+const viewToggle = (page: Page, label: string) =>
+  page.getByRole('checkbox', { name: `Show ${label} in the navigation` });
+
+async function openNavigationSettings(page: Page): Promise<void> {
+  await page.getByTestId('nav-settings').click();
+
+  const section = page.locator(
+    'config-page config-section[heading="Navigation"] .header',
+  );
+
+  await expect(section).toBeVisible();
+
+  if ((await section.getAttribute('aria-expanded')) === 'false') {
+    await section.click();
+  }
+
+  await expect(section).toHaveAttribute('aria-expanded', 'true');
+}
+
+test.describe('configurable destinations', () => {
+  test('Autotag is off by default and Downloads needs a client', async ({
+    app,
+  }) => {
+    await expect(app.getByTestId('nav-home')).toBeVisible();
+
+    await expect(app.getByTestId('nav-autotag')).toHaveCount(0);
+    await expect(app.getByTestId('nav-downloads')).toHaveCount(0);
+  });
+
+  /**
+   * Hiding takes the item away and nothing else. Detail views navigate
+   * into these and the launch page is one of them, so a destination
+   * with no nav item still has to open.
+   */
+  test('a hidden destination is still reachable', async ({ app }) => {
+    await navigateTo(app, 'autotag');
+
+    await expect(app.getByTestId('main-content')).toHaveAttribute(
+      'data-active-view',
+      'autotag',
+    );
+
+    // And nothing is falsely lit while standing on it -- the same rule
+    // a detail view follows, with no special case for either.
+    await expect(navItem(app, 'Home')).toHaveAttribute('aria-current', 'false');
+  });
+
+  test('switching Autotag on adds it to the sidebar', async ({ app }) => {
+    await openNavigationSettings(app);
+
+    await viewToggle(app, 'Autotag').check();
+
+    await expect(app.getByTestId('nav-autotag')).toBeVisible();
+
+    // Clicking it is the point of having it.
+    await app.getByTestId('nav-autotag').click();
+    await expect(app.getByTestId('main-content')).toHaveAttribute(
+      'data-active-view',
+      'autotag',
+    );
+
+    // Put it back, or the next spec against this app sees a library
+    // this one changed.
+    await openNavigationSettings(app);
+    await viewToggle(app, 'Autotag').uncheck();
+    await expect(app.getByTestId('nav-autotag')).toHaveCount(0);
+  });
+
+  /**
+   * Settings has no toggle at all, rather than a toggle that refuses:
+   * a user who hides it cannot get back to unhide it. The backend
+   * refuses it too, because `config.toml` is hand-editable.
+   */
+  test('Settings cannot be switched off', async ({ app }) => {
+    await openNavigationSettings(app);
+
+    await expect(viewToggle(app, 'Settings')).toBeDisabled();
+    await expect(app.getByTestId('nav-settings')).toBeVisible();
+  });
+
+  /**
+   * The launch page is refused while it is the launch page, which is a
+   * state the user can leave by changing the launch page above it.
+   */
+  test('the launch page cannot be switched off', async ({ app }) => {
+    await openNavigationSettings(app);
+
+    await expect(viewToggle(app, 'Home')).toBeDisabled();
+  });
+});