Add opentracing-types to dev dependencies

[H-Shay]

As the title states, pulls in types for opentracing from opentracing-types. Has the added bonus of bumping the mypy precision rate to above 80%.

[DMRobertson]

LGTM!

[DMRobertson]

But having said that, any idea why this is necessary?

[H-Shay]

Honestly not entirely! I know in a previous conversation, there was discussion about jaeger.Tracer inheriting from Tracer: #275 (comment) but mypy doesn't seem to be picking that up and in a fit of pique I figured this was a pretty safe cast to make while fully expecting someone to call me on it.

[reivilibre]

sygnal/sygnal.py:156: error: Incompatible types in assignment (expression has type "Optional[jaeger_client.tracer.Tracer]", variable has type "opentracing.tracer.Tracer")  [assignment]

I think the problem is that it's Optional.

Clicking through to the function, I see:

    def initialize_tracer(self, io_loop: Optional[Any] = None) -> Optional[Tracer]:
        """
        Initialize Jaeger Tracer based on the passed `jaeger_client.Config`.
        Save it to `opentracing.tracer` global variable.
        Only the first call to this method has any effect.
        """

        with Config._initialized_lock:
            if Config._initialized:
                logger.warning('Jaeger tracer already initialized, skipping')
                return None
            Config._initialized = True

        tracer = self.new_tracer(io_loop)

        self._initialize_global_tracer(tracer=tracer)
        return tracer

I think my preferred approach would be to assert that it's not None. (I guess you have to do that before assigning it to the field so it's a little clunky, but I think less evil than a full on cast)

[H-Shay]

I thought that at first but when I added this code:

tracer = jaeger_cfg.initialize_tracer()
assert tracer is not None
self.tracer = tracer

the error persisted, which is why I thought it might be an issue with the inheritance not being clear to mypy.

[reivilibre]

I think that's because tracer already exists as a var with a different type annotation.

                    tr = jaeger_cfg.initialize_tracer()
                    assert tr is not None
                    self.tracer = tr

seems to work locally, though probably give it a nicer name :D

[H-Shay]

Yes indeed, I have fixed it.

[reivilibre]

thank you! :)