Macro to display model struct the way Flux does

[ericphanson]

Semi-related to #2043 😄. Custom model structs use

@functor MyModel

to define Functors.children etc. It would be nice if there was also

@define_layer_show MyModel

to generate a method for Base.show, like

using Flux
function Base.show(io::IO, m::MIME"text/plain", x::MyModel)
    if get(io, :typeinfo, nothing) === nothing  # e.g. top level in REPL
      Flux._big_show(io, x)
    elseif !get(io, :compact, false)  # e.g. printed inside a Vector, but not a Matrix
      Flux._layer_show(io, x)
    else
      show(io, x)
    end
  end
end

Alternatives:

• I guess this could also be built into @functor but I suspect it might be better to keep it separate/ opt-in so you can define your own show method if you want. Also, adding it to @functor would also presumably be breaking since folks may have custom show methods already and that would generate method overwrite warnings and possibly break precompilation.
• This could be done with an abstact type, but I think it's nice if folks are free to have their model partipicate in their own type hierarchy. But an abstract type seems OK too.

[mcabbott]

I had a go in #1932 .

But right now I think a supertype like #2028 might be cleaner than having an ever-expanding the zoo of things you ought to invoke for good behaviour. Do you know of examples in the wild where the type hierarchy would clash?

[ericphanson]

Do you know of examples in the wild where the type hierarchy would clash?

No, I don't.

But right now I think a supertype like https://github.com/FluxML/Flux.jl/pull/2028 might be cleaner than having an ever-expanding the zoo of things you ought to invoke for good behaviour.

Yeah, that makes sense. I actually do like the idea of a supertype to opt into nice fallbacks for common features; I think it's most problematic when it's a required part of the interface and you can't use Flux otherwise (rather than opting into some features). There's also always the wrapper thing of

struct MyModel{M<:FluxSuperType} <: MyCustomSuperType
    flux_model::M
end

folks can use if they need to.