Deprecate "Most Views" download order

YouTube's new listing layout means yt-dlp no longer returns `view_count`
in flat channel/playlist entries, so sorting by views raised KeyError and
the download failed and retried forever.

Sorting by views now requires per-video extraction (hundreds of requests
per channel), so the feature is deprecated rather than degraded:

- downloader: the 'views' branch raises UnrecoverableDownloadError so the
  download fails cleanly (no retry loop) with a message to switch to
  Newest/Oldest. May be revisited via the YouTube Data API.
- schema: download_order validation drops 'views' (newest/oldest/null only).
- UI: removed "Most Views" from the download-order dropdown.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/components/Vars.js

@@ -101,7 +101,7 @@ export const validUrlRegex = /^(http|https):\/\/[^ "]+$/;
 export const downloadOrderOptions = [
     {key: 'newest', text: 'Newest', value: 'newest'},
     {key: 'oldest', text: 'Oldest', value: 'oldest'},
-    {key: 'views', text: 'Most Views', value: 'views'},
+    // 'views'/'Most Views' was removed: YouTube no longer provides view counts in channel/playlist listings.
 ];
 
 export const downloadResolutionOptions = [

modules/videos/downloader.py

@@ -720,9 +720,12 @@ class ChannelDownloader(Downloader, ABC):
             logger.debug(f'Downloading oldest videos from {download.url}')
             downloads = downloads.reverse()
         elif sort_key == 'views':
-            # Download videos with most views.
-            logger.debug(f'Downloading most viewed videos from {download.url}')
-            downloads = sorted(downloads, key=lambda i: i['view_count'], reverse=True)
+            # YouTube no longer exposes `view_count` in flat channel/playlist listings, so we can no longer
+            # sort by views without fetching every video individually.  This may become possible again if we
+            # integrate the YouTube Data API.
+            raise UnrecoverableDownloadError(
+                'Downloading by "Most Views" is no longer supported because YouTube no longer provides view '
+                'counts in channel/playlist listings.  Please change this download to "Newest" or "Oldest".')
 
         # Limit the videos that will be downloads (this allows the user to download the "top 100" videos of a Channel)
         if video_count_limit := settings.get('video_count_limit'):

modules/videos/test/test_downloader.py

@@ -706,6 +706,27 @@ async def test_download_playlist(test_session, test_directory, mock_video_extrac
     }
 
 
+def test_get_missing_videos_views_order_deprecated(test_session):
+    """The 'views' download order was deprecated.  YouTube no longer provides `view_count` in flat
+    channel/playlist listings, so a download configured for 'views' raises an unrecoverable error rather
+    than crashing with a KeyError or silently downloading in the wrong order."""
+    from modules.videos.downloader import channel_downloader
+    # Flat entries no longer contain a `view_count` key (matches current yt-dlp behavior).
+    download = Download(
+        url='https://www.youtube.com/@example/videos',
+        settings={'download_order': 'views'},
+        info_json={'entries': [
+            {'_type': 'url', 'id': 'a', 'title': 'a', 'url': 'https://youtube.com/watch?v=a'},
+            {'_type': 'url', 'id': 'b', 'title': 'b', 'url': 'https://youtube.com/watch?v=b'},
+        ]},
+    )
+    test_session.add(download)
+    test_session.commit()
+
+    with pytest.raises(UnrecoverableDownloadError):
+        channel_downloader.get_missing_videos(test_session, download)
+
+
 @pytest.mark.asyncio
 async def test_channel_download_crud(test_session, async_client, assert_downloads, tag_factory):
     """Test creating more complex Channel Download."""

wrolpi/schema.py

@@ -301,8 +301,9 @@ class DownloadSettings:
         if not self.download_metadata_only:
             del self.download_metadata_only
 
-        if self.download_order not in (None, 'newest', 'oldest', 'views'):
-            raise ValidationError(f'Download order must be one of newest, oldest, views, or null.')
+        # 'views' was deprecated: YouTube no longer provides view counts in channel/playlist listings.
+        if self.download_order not in (None, 'newest', 'oldest'):
+            raise ValidationError(f'Download order must be one of newest, oldest, or null.')
 
         if self.video_format not in (None, 'mp4', 'mkv', 'ogg', 'webm'):
             raise ValidationError(f'Video format must be one of mp4, mkv, ogg, webm, or null.')

wrolpi/test/test_downloader.py

@@ -914,6 +914,20 @@ def test_download_settings_coerces_numeric_strings():
     assert 'max_pages' not in req.settings
 
 
+@pytest.mark.parametrize('order', ['newest', 'oldest', None])
+def test_download_settings_accepts_valid_download_order(order):
+    from wrolpi.schema import DownloadSettings
+    DownloadSettings(download_order=order)
+
+
+def test_download_settings_rejects_deprecated_views_order():
+    """'views' download order was deprecated; YouTube no longer provides view counts in listings."""
+    from wrolpi.schema import DownloadSettings
+    from wrolpi.errors import ValidationError
+    with pytest.raises(ValidationError):
+        DownloadSettings(download_order='views')
+
+
 @pytest.mark.asyncio
 async def test_downloads_config(test_session, test_download_manager, test_download_manager_config,
                                 test_downloader, assert_downloads, tag_factory, await_switches):