[bugfix]: distinguish dataset loading errors from empty lists

apps/fastvideo_studio/src/app/datasets/page.test.tsx

@@ -0,0 +1,64 @@
+import { act, fireEvent, render, screen } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+
+import { HeaderActionsProvider } from '@/components/shell/HeaderActionsContext';
+import { getDatasets, type Dataset } from '@/lib/api';
+
+import DatasetsPage from './page';
+
+vi.mock('@/lib/api', () => ({
+  getDatasets: vi.fn(),
+}));
+
+vi.mock('@/components/datasets/AddDatasetButton', () => ({
+  default: () => null,
+}));
+
+vi.mock('@/components/datasets/CreateDatasetModal', () => ({
+  default: () => null,
+}));
+
+vi.mock('@/components/datasets/DatasetCard', () => ({
+  default: ({ dataset }: { dataset: Dataset }) => <div>{dataset.name}</div>,
+}));
+
+function renderPage() {
+  return render(
+    <HeaderActionsProvider>
+      <DatasetsPage />
+    </HeaderActionsProvider>,
+  );
+}
+
+describe('DatasetsPage', () => {
+  it('shows loading content before the initial request settles', async () => {
+    let resolveDatasets: (datasets: Dataset[]) => void = () => {};
+    vi.mocked(getDatasets).mockReturnValue(
+      new Promise<Dataset[]>((resolve) => {
+        resolveDatasets = resolve;
+      }),
+    );
+
+    renderPage();
+    expect(screen.getByLabelText('Loading datasets')).toBeInTheDocument();
+    expect(screen.queryByText('No datasets yet.')).not.toBeInTheDocument();
+
+    act(() => resolveDatasets([]));
+    expect(await screen.findByText('No datasets yet.')).toBeInTheDocument();
+  });
+
+  it('shows API failures separately from an empty list and retries', async () => {
+    vi.spyOn(console, 'error').mockImplementation(() => {});
+    vi.mocked(getDatasets).mockRejectedValueOnce(new Error('network down'));
+
+    renderPage();
+    expect(
+      await screen.findByText(/Could not load datasets from the Studio API/),
+    ).toBeInTheDocument();
+    expect(screen.queryByText('No datasets yet.')).not.toBeInTheDocument();
+
+    vi.mocked(getDatasets).mockResolvedValueOnce([]);
+    fireEvent.click(screen.getByRole('button', { name: 'Try Again' }));
+    expect(await screen.findByText('No datasets yet.')).toBeInTheDocument();
+  });
+});

apps/fastvideo_studio/src/app/datasets/page.tsx

@@ -1,12 +1,14 @@
 'use client';
 
 import * as React from 'react';
+import { AlertTriangle } from 'lucide-react';
 
 import AddDatasetButton from '@/components/datasets/AddDatasetButton';
 import CreateDatasetModal from '@/components/datasets/CreateDatasetModal';
 import DatasetCard from '@/components/datasets/DatasetCard';
 import { HeaderActions } from '@/components/shell/HeaderActionsContext';
 import { Card } from '@/components/ui/card';
+import { Button } from '@/components/ui/button';
 import { useStore } from '@/hooks/useStore';
 import { getDatasets } from '@/lib/api';
 import type { Dataset } from '@/lib/api';
@@ -21,18 +23,28 @@ import {
 
 export default function DatasetsPage() {
   const [datasets, setDatasets] = React.useState<Dataset[]>([]);
+  const [isInitialLoading, setIsInitialLoading] = React.useState(true);
   const [error, setError] = React.useState<string | null>(null);
   const { open } = useStore(createDatasetModalStore);
+  const fetchSequence = React.useRef(0);
 
   const fetchDatasets = React.useCallback(async () => {
+    const sequence = ++fetchSequence.current;
     try {
-      setDatasets(await getDatasets());
-      setError(null);
+      const next = await getDatasets();
+      if (sequence === fetchSequence.current) {
+        setDatasets(next);
+        setError(null);
+      }
     } catch (err) {
       console.error('Failed to fetch datasets:', err);
-      // Distinguish an API outage from a genuinely empty list, so the user
-      // isn't told they have no datasets when the server is unreachable.
-      setError(err instanceof Error ? err.message : 'Failed to load datasets');
+      if (sequence === fetchSequence.current) {
+        setError(
+          'Could not load datasets from the Studio API. Check the server and try again.',
+        );
+      }
+    } finally {
+      if (sequence === fetchSequence.current) setIsInitialLoading(false);
     }
   }, []);
 
@@ -52,22 +64,61 @@ export default function DatasetsPage() {
       </HeaderActions>
       <main className="mx-auto flex w-full max-w-[850px] flex-col gap-6 px-4 pb-12">
         <Card className="p-6">
-          <div>
-            {error ? (
-              <p className="py-8 text-center text-destructive">{error}</p>
-            ) : datasets.length === 0 ? (
-              <p className="py-8 text-center text-muted-foreground">
-                No datasets yet.
-              </p>
-            ) : (
-              datasets.map((ds) => (
-                <DatasetCard
-                  key={ds.id}
-                  dataset={ds}
-                  onUpdated={fetchDatasets}
-                  onSelect={() => handleSelectDataset(ds)}
+          <div aria-busy={isInitialLoading}>
+            {isInitialLoading ? (
+              <div
+                aria-label="Loading datasets"
+                className="flex flex-col gap-3 py-2"
+              >
+                {[0, 1, 2].map((item) => (
+                  <div
+                    key={item}
+                    className="h-24 animate-pulse rounded-lg border border-border bg-muted/50"
+                  />
+                ))}
+              </div>
+            ) : error && datasets.length === 0 ? (
+              <div
+                role="alert"
+                className="flex flex-col items-center gap-3 py-8 text-center"
+              >
+                <AlertTriangle
+                  className="size-6 text-destructive"
+                  aria-hidden
                 />
-              ))
+                <p className="max-w-md text-sm text-muted-foreground">
+                  {error}
+                </p>
+                <Button type="button" variant="outline" onClick={fetchDatasets}>
+                  Try Again
+                </Button>
+              </div>
+            ) : (
+              <>
+                {error && (
+                  <p
+                    role="status"
+                    className="mb-3 rounded-lg border border-amber-500/50 bg-amber-500/10 px-3 py-2 text-sm text-foreground"
+                  >
+                    Dataset updates are temporarily unavailable. Showing the
+                    most recent results.
+                  </p>
+                )}
+                {datasets.length === 0 ? (
+                  <p className="py-8 text-center text-muted-foreground">
+                    No datasets yet.
+                  </p>
+                ) : (
+                  datasets.map((ds) => (
+                    <DatasetCard
+                      key={ds.id}
+                      dataset={ds}
+                      onUpdated={fetchDatasets}
+                      onSelect={() => handleSelectDataset(ds)}
+                    />
+                  ))
+                )}
+              </>
             )}
           </div>
         </Card>