We move some of the data setup to the top of the file.
We also remove some get_sub() calls that aren't really
necessary now that peer_data and stream_data are more
independent.
The maybe_clear_subscribers() function was an artifact of
when we used to attach subscribers to the "sub" records in
stream_data.js. I think it was basically a refactoring
shim, and due to some other recent cleanup, it was only
used in test code.
We also change how we validate stream ids.
Going forward, peer_data just looks up stream_ids with the
normal stream_data API when it's trying to warn about
rogue stream_ids coming in. As I alluded to in an earlier
commit, some of the warning code here might be overly
defensive, but at least it's pretty self-contained.
We now use the same code in all places to
get the bucket of user_ids that correspond
to a stream, and we consistently treat
a stream as having zero subscribers, not
an undefined number of subscribers, in
the hypothetical case of us asking about
a stream that we're not tracking.
The behavior for untracked streams has
always been problematic, since if a
stream is untracked, all bets are off.
So now if we don't "track" the stream,
the subscriber count is zero. None of
our callers distinguish between undefined
and zero.
And we just consider the stream to be subscribed
by a user when add_subscriber is called,
even if we haven't been told by stream_data
to track the stream. (We also stop
returning true/false from add_subscriber,
since only test code was looking at it.)
We protect against the most likely source
of internal-to-the-frontend bugs by adding
the assert_number() call.
We generally have to assume that the server
is sending us sensible data at page load
time, or all bets are off.
And we have good protections in place
for unknown ids in our dispatch code
for peer_add/peer_remove events.
Steve Howell