AssertionError when expliciting the scale when mapping a variable to another of the same scale

[Samuel-amap]

Trying to map a variable to the previous timestep of another variable at the same scale yields the following error :

ERROR: AssertionError: Variable `in_day_summed_prev_timestep` is mapped to its own scale in organ Default. This is not allowed.

Here's a minimal example to reproduce the error, with a model that simply increments, and the other that passes the result without changing it :

PlantSimEngine.@process "ToyAdd1" verbose = false

struct MyToyAdd1Model <: AbstractToyadd1Model end

PlantSimEngine.inputs_(m::MyToyAdd1Model) = (in_summed_prev_timestep=-Inf,)
PlantSimEngine.outputs_(m::MyToyAdd1Model) = (out_summed=-Inf,)

function PlantSimEngine.run!(m::MyToyAdd1Model, models, status, meteo, constants=nothing, extra=nothing)
    status.out_summed = meteo.data + status.in_summed_prev_timestep
end

PlantSimEngine.@process "ToyNoop" verbose = false

struct MyToyNoopModel <: AbstractToynoopModel end

PlantSimEngine.inputs_(m::MyToyNoopModel) = (out_summed=-Inf,)
PlantSimEngine.outputs_(m::MyToyNoopModel) = (out_summed_2= -Inf,)

function PlantSimEngine.run!(m::MyToyNoopModel, models, status, meteo, constants=nothing, extra=nothing)
    status.out_summed_2 = status.out_summed
end

mapping = Dict(
  "Default"=> (
    MultiScaleModel(
        model=MyToyAdd1Model(),
        mapped_variables=[
            PlantSimEngine.PreviousTimeStep(:in_summed_prev_timestep) => "Default" => :out_summed_2,
            ]),               
            MyToyNoopModel(),
   
        Status(in_summed_prev_timestep=0,out_summed_2=0,)
  ),
)

mtg = Node(MultiScaleTreeGraph.NodeMTG("/", "Default", 1, 1))
df = DataFrame(:data => [1 for i in 1:365], )
out = run!(mtg, mapping, df)

If one replaces

PlantSimEngine.PreviousTimeStep(:in_summed_prev_timestep) => "Default" => :out_summed_2,

with

PlantSimEngine.PreviousTimeStep(:in_summed_prev_timestep) => :out_summed_2,

Then there are no issues.

Reasonable choices that come to mind : we can keep the behaviour as is, but change the error message to indicate the expected API usage (and warn 'are you sure you intended to map to the same scale ?'), or change the behaviour to fully allow that syntax.

In any case, there is a problem with the error message.