Deprecate clock_tick context manager

[multigl]

• backwards compatible deprecation of clock_tick context manager
• ensure activity set when changing temporal properties and model clocked with activity_cls
• session and mapper event life cycle tests

[multigl]

Resolves #28

[dargueta-work]

You might want to use return self here, because otherwise any attempt to access reset_activity or activity_required from an instance of a class using it will crash with an AttributeError:

A minimal example:

import types

ns = types.SimpleNamespace(activity=1)

# This works
ActivityState.reset_activity(ns, None)

class B:
    astate = ActivityState()

# This crashes
B.astate.reset_activity(ns, None)

[dargueta-work]

Same idea here about returning self.

[multigl]

@NicoleZuckerman this the expire for the activity descriptor

[multigl]

@NicoleZuckerman this is the expire for the current_clock descriptor

[multigl]

relevant sqlalchemy documentation on instance events: http://docs.sqlalchemy.org/en/rel_1_1/orm/events.html#instance-events

[dargueta-work]

Using getattr with a string constant like this is equivalent to instance.vclock. This will still crash with an AttributeError unless you pass a default value as the third argument. Did you mean to do that?

vclock = getattr(instance, 'vclock', 0)

[dargueta-work]

Same note here about using getattr without a default argument.

However, be warned: attributes starting with double underscores may not behave as you expect. Python has a concept of "private variables" that may result in an AttributeError getting thrown.

From the docs:

Any identifier of the form __spam (at least two leading underscores, at most one trailing underscore) is textually replaced with _classname__spam, where classname is the current class name with leading underscore(s) stripped. This mangling is done without regard to the syntactic position of the identifier, as long as it occurs within the definition of a class.

Because it's required to occur inside the class definition I think this will be okay, but I thought I'd point it out.

[multigl]

yeah, I think in this case it's okay, but it's a good call out

[dargueta-work]

Can we put an error message here please? It'll make debugging easier. I think the original error message might suffice.

[multigl]

👍 should probably be:

raise ValueError("activity is missing on edit") from None

[dargueta-work]

return isn't necessary at the end of a function. You can remove this.

[multigl]

I left it in so it looks less confusing to me, but I'm strange that way 😆

[multigl]

looking good, looking real good

[multigl]

this is pretty neat, might also want to refetch the model from the first session and see that the vclock is two there

[multigl]

I wonder if we want to assert that it's an instance of ClockTick (or whatever it actually is) and has properties we expect?

[multigl]

yesssss

[dargueta-work]

Can we change this error message to something a bit more helpful? 🙂 Perhaps:

if instance.temporal_options.activity_cls:
    raise RuntimeError(
        "Can't set activity state on instance of %r because the activity class is None."
        % type(instance).__name__)

(That's assuming that my interpretation of this assertion is correct.)