Modifying var specs (related to time-varying)

[tclune]

(See also #3057)

As currently implemented in MAPL3, VarSpecs are created in SetServices and then used to create corresponding StateItemSpec's at the beginning of the first init phase (initialize_advertise). For time-varying specs (including delayed specs for ExtData), we must decide where the modification will go. E.g., if a user modifies a var spec after it has been converted to a StateItemSpec, it will have no affect. And if the StateItemSpec is modified after an ESMF FIeld has been allocated, it will also have no affect on(as things are currently implemented.)

First we need a sensible convention, and then ideally a mechanism to enforce it.

The simplest approach to my understanding would be to have any modifications happen to the StateItemSpec. I.e., MAPL_GridcompSetItemAspect(<state>, short_name, aspect) would only be permitted after initialize_advertise() (or really after that variable has been "advertised".

The behavior of this call will then depend on whether it is before or after the field has been allocated. (Note: allocation happens after connections have been processed.) Here is my proposal:

1. Introduce a StateItemStatus_Flag analogous to ESMF_Field_StatusFlag. The supported states:

   • STATEITEMSTATUS_INVALID (pre creation)
   • STATEITEMSTATUS_CREATED
   • STATEITEMSTATUS_GEOMSET (possibly not needed)
   • STATEITEMSTATUS_COMPLETE

2. Behavior of SetAspect depends on the status as follows:

   • DNE - short name not found: error

   • INVALID - StateItemExists

   • CREATED

     • Allow modification - even for "time-dependent" aspects.
     • Alternative: only allow Set for aspects that have not been specified yet
     • Do not deallocate/reallocate

   • COMPLETE - depends on aspect

     • not time dependent: error
       • always applies to CLASS, ATTRIBUTES, UNGRIDDED, FREQUENCY
     • GEOM, VGRID, TYPEKIND
       a. set aspect
       b. reallocate
       c. signal couplers (signal terminaton at couplers that addresses given aspect)
     • Units (no need to reallocate)
       a. signal couplers

     @atrayano @bena-nasa @pchakraborty @darianboggs