add NoShow as an (orthogonalised) alternative

src/Fluxperimental.jl

@@ -13,6 +13,9 @@ include("chain.jl")
 
 include("compact.jl")
 
+include("noshow.jl")
+export NoShow
+
 include("new_recur.jl")
 
 end # module Fluxperimental

src/compact.jl

@@ -156,7 +156,7 @@ function Flux._big_show(io::IO, obj::CompactLayer, indent::Int=0, name=nothing)
   setup_strings = obj.setup_strings
     layer, input, block = obj.strings
     pre, post = ("(", ")")
-    println(io, " "^indent, "@compact", pre)
+    println(io, " "^indent, isnothing(name) ? "" : "$name = ", layer, pre)
     for k in keys(obj.variables)
       v = obj.variables[k]
       if Flux._show_leaflike(v)

src/noshow.jl

@@ -0,0 +1,60 @@
+
+"""
+    NoShow(layer)
+    NoShow(string, layer)
+
+This alters printing (for instance at the REPL prompt) to let you hide the complexity
+of some part of a Flux model. It has no effect on the actual running of the model.
+
+By default it prints `NoShow(...)` instead of the given layer.
+If you provide a string, it prints that instead -- it can be anything,
+but it may make sense to print the name of a function which will
+re-create the same structure.
+
+# Examples
+
+```jldoctest
+julia> Chain(Dense(2 => 3), NoShow(Parallel(vcat, Dense(3 => 4), Dense(3 => 5))), Dense(9 => 10))
+Chain(
+  Dense(2 => 3),                        # 9 parameters
+  NoShow(...),                          # 36 parameters
+  Dense(9 => 10),                       # 100 parameters
+)                   # Total: 8 arrays, 145 parameters, 1.191 KiB.
+
+julia> PseudoLayer((i,o)::Pair) = Parallel(+, Dense(i => o, relu), Dense(i => o, tanh));
+
+julia> mid = PseudoLayer(3 => 10);
+
+julia> Chain(Dense(2 => 3), NoShow("PseudoLayer(3 => 10)", mid), Dense(9 => 10))
+Chain(
+  Dense(2 => 3),                        # 9 parameters
+  PseudoLayer(3 => 10),                 # 80 parameters
+  Dense(9 => 10),                       # 100 parameters
+)                   # Total: 8 arrays, 189 parameters, 1.379 KiB.
+```
+"""
+struct NoShow{T}
+    str::String
+    layer::T
+end
+
+NoShow(layer) = NoShow("", layer)
+
+Flux.@functor NoShow
+
+(no::NoShow)(x...) = no.layer(x...)
+
+Base.show(io::IO, no::NoShow) = print(io, isempty(no.str) ? "NoShow(...)" : no.str)
+
+Flux._show_leaflike(::NoShow) = true  # I think this is right
+Flux._show_children(::NoShow) = (;)   # Seems to be needed?
+
+function Base.show(io::IO, ::MIME"text/plain", m::NoShow)
+  if get(io, :typeinfo, nothing) === nothing  # e.g., top level of REPL
+    Flux._big_show(io, m)
+  elseif !get(io, :compact, false)  # e.g., printed inside a Vector, but not a matrix
+    Flux._layer_show(io, m)
+  else
+    show(io, m)
+  end
+end