fix: honor maxPlaylistRetries for single-media HLS playlists

[cpruijsen]

Description

Single HLS media playlists (no master) stop retrying once playlistErrors_ exceeds maxPlaylistRetries. Fixes #1596.

maxPlaylistRetries did not stop playlist reloads when the source was a single HLS media playlist (no master). excludePlaylist retried the only playlist whenever playlistExclusionDuration was finite, and never reached the existing playlistErrors_ > maxPlaylistRetries check that indefinitely excludes a variant on a multi-rendition master.

A single media playlist is still retried while playlistErrors_ is within the cap (default remains Infinity). Once the cap is exceeded, the playlist is excluded forever and playback errors, same as the existing "exclude the only playlist only if excluded forever" path.

The reporter reproduced infinite retries on a single media .m3u8 and confirmed the cap already works with a master that has multiple variants. README documents that retry attempts must exceed maxPlaylistRetries before indefinite exclusion.

The change skips the single-playlist early return when playlistErrors_ exceeds maxPlaylistRetries. The other option was to set playlistExclusionDuration to Infinity when retries are exhausted, and leave the early-return condition unchanged. Skipping the early return matches the later playlistErrors_ check in the same function and the existing "only playlist / excluded forever" behavior. Smallest reversible change. Happy to switch to the duration-to-Infinity approach if that is preferred.

Specific Changes proposed

• src/playlist-controller.js: do not retry the only playlist once playlistErrors_ exceeds maxPlaylistRetries.
• test/playlist-controller.test.js: cover a media-only source (manifest/media.m3u8) with maxPlaylistRetries: 1. First error retries, second error excludes forever and errors.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

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