Cannot record values in sub-scenarios of a modular scenario

[abol-karimi]

The simulation result of a modular scenario does not contain the records dictionary of the records statements in the setup sections of its sub-scenarios.

[Eric-Vin]

Can reproduce this behavior with the following example:

param map = localPath('assets/maps/CARLA/Town05.xodr')
param carla_map = 'Town05'
param time_step = 1.0/10

model scenic.domains.driving.model

scenario Sub():
    setup:
        record "FOO" as "foo"

scenario Main():
    setup:
        ego = new Car
        record "BAR" as "bar"
    compose:
        do Sub()

[dfremont]

The root issue is that I didn't expect record to be used anywhere except at the top level. We could extend it to support sub-scenarios, but the best semantics isn't totally clear to me. The difficulty is that if multiple copies of the sub-scenario are invoked, the records will conflict: for example if the compose block above were do Sub(), Sub() (two copies of Sub in parallel) or do Sub(); do Sub() (two copies in sequence). I think the least surprising behavior for plain record would be for Scenic to raise an error in the parallel case and concatenate the time series in the sequential case. @abol-karimi would that work for your use case?

For record initial and record final, I can't see any way to make those work in a backwards-compatible way when the scenario is invoked multiple times, so I think we should just raise an error. I could see potential applications for saving a value each time a sub-scenario is invoked, but since the result would still be a time series, it wouldn't fit with the documented behavior of record initial/final as producing a single value in the records dictionary. (I suppose we could have the value be a time series if and only if the sub-scenario runs multiple times, but all user code reading the record would have to check for both cases, so I'm not sure if it's worth the complexity.)

[abol-karimi]

It works perfectly fine for me (i.e. runtime error for parallel, concatenation for serial.) My use case for modular scenarios is mainly re-usability and managing the complexity, and I don't invoke multiple instances of a scenario.