Add signal reservations

[ahopkins]

It occurred to me while writing documentation for #1630/#2042 that there were certain patterns of names that we probably do not want people to start declaring on their own. We do not know exactly what those patterns are yet, but I thought it might make sense to lock in some reserved names so people do not start implementing them now, and then end up with weird behaviors down the road.

Basically, that means we are adding some code right now that will be temporary. Or, at the very least will change.

Perhaps I am being overly cautious. Thoughts? Do we need this? Is the list complete enough for now?

Current reservations:

• Anything starting server.
• Anything starting http.
• Anything starting sanic. that is not sanic.notice. or sanic.log.

[codecov]

Codecov Report

Merging #2060 (2a0fe66) into master (d4660d0) will increase coverage by 0.014%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master     #2060       +/-   ##
=============================================
+ Coverage   92.176%   92.190%   +0.014%     
=============================================
  Files           38        38               
  Lines         3451      3457        +6     
  Branches       580       581        +1     
=============================================
+ Hits          3181      3187        +6     
  Misses         184       184               
  Partials        86        86               

Impacted Files	Coverage Δ
sanic/signals.py	93.056% <100.000%> (+0.631%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d4660d0...2a0fe66. Read the comment docs.

[ashleysommer]

that is not sanic.notice. or sanic.log.

Is the thought that the user might want to handle potential future sanic.notice.* and sanic.log.* events themselves?

[ashleysommer]

reservation.reference cannot be None here. We call reservation.reference.split(",") above, so it must be a string. It it was None, Line 158 would throw and exception.
Do we need to move if reservation.reference is None: continue to above line 155?

[ahopkins]

Good catch. Again, maybe I am overcomplicating and the whole thing should just be:

parts = event.split(",")
if parts[0] in ("server", "http", "sanic"):
    raise InvalidSignal

And then worry about any more complicated logic when we get to it.

[ashleysommer]

Yep. I'd go with the simpler solution for now. We can think about reservation rules and how they are matched against signals, in the future.

[ahopkins]

Okay, I updated it to only be reserved namespaces http and server.

I want to push people (via the docs) to get used to using sanic.notice.something when they have a simple use case and a full blown namespaced event doesn't make sense.

[ahopkins]

that is not sanic.notice. or sanic.log.

Is the thought that the user might want to handle potential future sanic.notice.* and sanic.log.* events themselves?

I think these might be names we want to control. Probably also sanic.exception.*. But, perhaps this is too much limitation. Maybe we just disallow them from defining anything that is server, http , or sanic and leave it at that.