Every emitted frame must carry the source byte offset of the packet it
came from. That held only for video for as long as it existed, and
nothing asserted it, so nothing caught it: ten parsers built frames with
`source: None` and a multi-clip title could not place audio or subtitles
by byte at all.
Finding them took a brace-balanced scan of the tree by hand — a regex
cannot do it, because a Frame literal contains nested braces and a
non-greedy match stops at the first `}`, which is how five sites survived
the first pass. This is that scan, as a test.
A second test fails if a codec module is added and not listed, since an
unchecked parser is exactly how the gap persists. Modules that emit no
Frame are named explicitly rather than skipped silently.
The guard tripped on itself twice while being written — first on its own
doc comment, then on its own string literals — so it strips line comments
and excludes its own module. A check that matches prose about the defect
rather than the defect is the same mistake in a different place.
Matthew Jackson
282651186c