@extend does not work with parameters

[baggepinnen]

When using @mtkmodel and @extend, the constructor does not know about the parameters of the extended system. MWE:

@mtkmodel Inner begin
    @parameters begin
        color[1:4] = [1.0, 0.0, 0.0, 1.0], [description = "Color of the body in animations"]
        render = true, [description = "Render the joint in animations"]
    end
end

@mtkmodel Outer begin
    @extend () = v = Inner()
    @parameters begin
        radius = 0.1, [description = "Radius of the sphere in animations"]
    end
end

@named test = Outer(color=[1,1,1,1])

julia> @named test = Outer(color=[1,1,1,1])
ERROR: MethodError: no method matching __Outer__(; name::Symbol, color::Vector{Int64})

Closest candidates are:
  __Outer__(; name, radius) got unsupported keyword argument "color"
   @ Main ~/.julia/packages/ModelingToolkit/UXr3S/src/systems/model_parsing.jl:138

[ven-k]

One must list all the args (parameter or variable), of a sub-component or a base-system, that should be added to the arglist of the main-component.

This will fix the issue:

@mtkmodel Outer begin
     @extend () = v = Inner(; color, render)
     @parameters begin
         radius = 0.1, [description = "Radius of the sphere in animations"]
     end
 end

[baggepinnen]

The component that is extended may have 10s-100s of parameters and variables, if we have to type them all out it kind-of defeats the purpose of extending something in the first place?

[ven-k]

It was mainly to keep the syntax same in both cases. If it is more convenient, I can modify the case for extend to automatically add all args.

[baggepinnen]

I can modify the case for extend to automatically add all args.

That sounds good to me, and aligns with what I would expect from inheritance