Set AttrW After Put

[shihab-dls]

It was found that setting an AttrRW would update the AttrR, but not the AttrW. This was because we must now do:

op.done()
pv.post(value)

However, it seems that the value you get for an Enum in value = op.value() is in the form ntenum(3, TTLIN4.VAL) (for example), which is correctly converted to the FastCS value <Labels.TTLIN4.VAL: 4> (for example), but a value in the form of:

{
                "index": attribute.datatype.index_of(value),
                "choices": attribute.datatype.names,
            }

must be passed in the pv.post(). This has led to this addition:

        if isinstance(self._attr_w.datatype, Enum):
            pv.post(cast_to_p4p_value(self._attr_w, cast_value))
        else:
            pv.post(value)

in order to cast the value to the write form.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.56%. Comparing base (a2a7808) to head (eceea0e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #292      +/-   ##
==========================================
+ Coverage   90.55%   90.56%   +0.01%     
==========================================
  Files          69       69              
  Lines        2414     2417       +3     
==========================================
+ Hits         2186     2189       +3     
  Misses        228      228              

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[GDYendell]

What happens on the client if put raises an exception and op.done() is not called? I am wondering if what we are supposed to do when a put fails is call op.done() but not pv.post. Is there any guidance on this? Any thoughts @coretl?

[coretl]

op.done(error=msg)
https://epics-base.github.io/p4p/server.html#p4p.server.ServerOperation.done