A full rescan wiped cover_image_path for every PDF/EPUB living in a
metadata.json (or metadata.opf-less) folder with no cover.jpg next to
the book: the sidecar branches returned early after findSidecarCover
missed, and mergeMetadata has no PDF/EPUB cover logic of its own. Four
books lost their thumbnails while their {file}.cover.jpg files still sat
on disk - most visibly the Audiobookshelf-managed No Starch titles.
Both sidecar branches now fall through to an embedded-cover fallback
(PDF via extractPDFCover, EPUB/KEPUB via extractEPUBCover) whenever no
sidecar cover file exists. Comics are untouched: mergeMetadata already
extracts their covers from the archive.
Adds TestSidecarCoverFallback with a hand-built one-page PDF carrying a
JPEG XObject plus a metadata.json sidecar, asserting the sidecar title
wins while the cover still comes from the file. Verified live: rescans
restored all four dereferenced covers with no leftover rows.
John O'Keefe
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