Poll the adapter's preview index until the adapter has exited, handing each
newly listed document to onPreview after verifying it. The index is read
once more after the adapter settles, so a tree published just before exit
is never missed. Any malformed index or tree rejects the watch: a preview
that cannot be verified is an import failure, not a skipped preview.
Poll the adapter's preview index until the adapter has exited, handing each newly listed document to
onPreviewafter verifying it. The index is read once more after the adapter settles, so a tree published just before exit is never missed. Any malformed index or tree rejects the watch: a preview that cannot be verified is an import failure, not a skipped preview.