👌 IMPROVE: Add full typing, type checking and test coverage

[chrisjsewell]

Hey guys, as the title suggests!

I've also dropped python 3.5 support (as we have also done in aiida-core), added a tox testing configuration, added codecov reporting, and updated the documentation build/ci.

All the tests should pass, except I have left some # TODOs regarding some type clarifications and possible errors detected:

plumpy/communications.py:29:2: W0511: TODO identifier type? (fixme)
plumpy/communications.py:146:2: W0511: TODO type of task and msg; dict? (fixme)
plumpy/ports.py:306:2: W0511: TODO this was set to None, but that would fail if you tried to compute breadcrumbs (fixme)
plumpy/utils.py:72:2: W0511: TODO I deleted ListenContext and ThreadSafeCounter, (fixme)
plumpy/__init__.py:22:2: W0511: TODO I deleted stack.py, because is not used or tested any where in this code base, or in aiida-core (fixme)
plumpy/process_comms.py:31:2: W0511: TODO process result/status type? (fixme)
plumpy/workchains.py:387:2: W0511: TODO this was added (fixme)
plumpy/process_states.py:253:2: W0511: TODO error: "Kill" has no attribute "result"/"successful" (fixme)
plumpy/base/state_machine.py:250:2: W0511: TODO should class initialise sealed = False? (fixme)
plumpy/base/state_machine.py:257:2: W0511: TODO this appears to never be used? (fixme)
plumpy/persistence.py:646:2: W0511: TODO according to types self._callbacks should first be called, i.e. self._callbacks() (fixme)

over to you 😬

[muhrin]

Thanks Chris! Looks good to me, let see if the others are happy before merging.

[codecov-io]

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[chrisjsewell]

plumpy/process_states.py:253:2: W0511: TODO error: "Kill" has no attribute "result"/"successful" (fixme)

This is not covered by testing, so is likely to be a legitimate bug (potentially related to aiidateam/aiida-core#3888)

[unkcpz]

Thanks @chrisjsewell, this really a helpful feature to have type hint. Just some minor request.

Out of curious, when we calling methods with the wrong type, what information will be given to the user? Is type hint only a hint or it really do the type check?

[chrisjsewell]

Thanks @chrisjsewell, this really a helpful feature to have type hint. Just some minor request.

right this all works now, and requests have been addressed, so I will be merging very shortly; so speak now or for ever hold your peace 😉

Out of curious, when we calling methods with the wrong type, what information will be given to the user? Is type hint only a hint or it really do the type check?

type hinting is not used at all at runtime, it is effectively stripped from the code.
But it allows for better auto-completion in editors and for dependant packages to type check against classes/functions used from this package.

Once this is released, I can add proper type hinting/checking to the aiida-core engine code, which I think will be very useful for users/plugin developers writing workflows etc

[unkcpz]

Thanks! all looks good to me.