WIP: Flow decorator

[davidwaroquiers]

Summary

This is a WIP PR trying to develop the flow decorator (see idea #416, also linked to #450). Seems like we could have another option to do what we want. Currently in a (very) proof-of-concept phase (previous attempt with abstract syntax trees failed).

Currently works for "simple" flows (i.e. flows of jobs), and only if the script creates only one flow. I think it should be generalizable, but before spending more time, I'd like to get some feedback from @utf, @Andrew-S-Rosen, @janosh, and maybe others. Basically, it works by adding a reference to the created jobs and flows into a "global" variable (I used the singleton from monty, not a standard python global variable, not exactly sure if it is needed and/or if it helps and/or what it adds in this specific case).

Using what @Andrew-S-Rosen did for having something more user friendly (see #450).

Currently breaks @janosh magic methods.

Another addition should be that the flow output is stored in the database somehow ? (some things to be made sure here though, we don't want to duplicate outputs both in jobs and flows).

Example in test_flows.py:test_flow_decorator

TODO (if any)

If this is a work-in-progress, write something about what else needs to be done.

• Generalize to complex flows
• Flow outputs in the results database ?
• Tests

Checklist

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