Add type hints

[kasium]

Requirement - what kind of business use case are you trying to solve?

As you might know many python3 only packages already have type hints present based on the typing module. Afterwards the types can be checked e.g. with mypy. It would be great if you could add type hints and mark the package as types (aka add a py.typed file)

Problem - what in Jaeger blocks you from solving the requirement?

Missing type hints in the code base

Proposal - what do you suggest to solve the problem or improve the existing situation?

Add type hints 😄

[kasium]

@yurishkuro I'm happy to give a contribution a try. However, I guess with the current support python versions it will get hard. I would recommend to drop at least python 3.5 support if not even 3.6. What do you think?

[yurishkuro]

yes, it's fine to raise min supported version (in separate PR)

[kasium]

So, should I just change the setup.py file or also other stuff?

[yurishkuro]

Also GitHub actions

[kasium]

@yurishkuro so I see the following needed types

• reporter ( Add types to reporter #333 )
• config ( Add types to config #334 )
• util ( Add basic typing support #326 )
• tracer ( Add typing to tracer.py #328 )
• span ( Add types for span, metrics, throttler #336 )
• metircs ( Add types for span, metrics, throttler #336 )
• throttler ( Add types for span, metrics, throttler #336 )
• sampler ( Add sampler types and py.typed file #338 )
• py.typed file ( Add sampler types and py.typed file #338 )

Can you please check if something is missing or is too much

[yurishkuro]

yep, looks just right

[kasium]

@yurishkuro I currently hit an issue with my latest types (local change)

ImportError while loading conftest '/root/git/jaeger-client-python/tests/conftest.py'.
tests/conftest.py:17: in <module>
    from jaeger_client import ConstSampler, Tracer
jaeger_client/__init__.py:18: in <module>
    from .tracer import Tracer  # noqa
jaeger_client/tracer.py:35: in <module>
    from .span import Span, SAMPLED_FLAG, DEBUG_FLAG
jaeger_client/span.py:26: in <module>
    from .tracer import Tracer
E   ImportError: cannot import name 'Tracer' from 'jaeger_client.tracer' (/root/git/jaeger-client-python/jaeger_client/tracer.py)

This happens because tracer.py imports span.py, but span.py needs tracer.py to type the constructor. So I would need the if TYPE_CHECKING construct which will decrease the coverage

[yurishkuro]

Does mypy have any means of adding types without explicit imports?

If no other solution, we'd have to take a hit on the coverage.