Julia 1.5 breaks @bind

[fonsp]

Posted by @cormullion on zulip:

[fonsp]

Can you do Pkg.status() in the terminal where you launched Pluto and send a screenshot?

[fonsp]

And can you create a cell with this content:

methods(Base.peek)

and send me the result?

[cormullion]

Closing Pluto... Restart Julia for a fresh session. 

Have a nice day! 🎈

(@v1.5) pkg> st
Status `~/.julia/environments/v1.5/Project.toml`
  [537997a7] AbstractPlotting v0.11.2
  [c52e3926] Atom v0.12.15
  [336ed68f] CSV v0.7.1
  [159f3aea] Cairo v1.0.3
  [d3e213a1] ColorSchemeTools v0.2.0
  [35d6a980] ColorSchemes v3.9.0
  [5ae59095] Colors v0.12.2
  [a93c6f00] DataFrames v0.21.3
  [e30172f5] Documenter v0.25.0
  [186bb1d3] Fontconfig v0.4.0
  [916415d5] Images v0.22.3
  [682c06a0] JSON v0.21.0
  [e5e0dc1b] Juno v0.8.2
  [ae8d54c2] Luxor v2.2.0 `~/.julia/dev/Luxor`
  [ee78f7c6] Makie v0.11.0
  [91a5bcdd] Plots v1.4.4
  [c3e4b0f8] Pluto v0.9.11
  [7f904dfe] PlutoUI v0.3.0
  [c46f51b8] ProfileView v0.6.5
  [d330b81b] PyPlot v2.9.0
  [8b424ff8] Thebes v0.0.0 `~/.julia/dev/Thebes`



julia> methods(Base.peek)
# 11 methods for generic function "peek":
[1] peek(s::Base.Iterators.Stateful) in Base.Iterators at iterators.jl:1274
[2] peek(s::Base.Iterators.Stateful, sentinel) in Base.Iterators at iterators.jl:1274
[3] peek(t::REPL.Terminals.TTYTerminal, ::Type{T}) where T in REPL.Terminals at /Applications/Julia-1.5.app/Contents/Resources/julia/share/julia/stdlib/v1.5/REPL/src/Terminals.jl:163
[4] peek(io::Base.AbstractPipe, ::Type{T}) where T in Base at io.jl:358
[5] peek(from::Base.GenericIOBuffer, T::Union{Type{Float16}, Type{Float32}, Type{Float64}, Type{Int128}, Type{Int16}, Type{Int32}, Type{Int64}, Type{UInt128}, Type{UInt16}, Type{UInt32}, Type{UInt64}}) in Base at iobuffer.jl:175
[6] peek(from::Base.GenericIOBuffer, ::Type{UInt8}) in Base at iobuffer.jl:224
[7] peek(s::IOStream, ::Type{UInt8}) in Base at iostream.jl:528
[8] peek(s::Base.LibuvStream, ::Type{T}) where T in Base at stream.jl:1196
[9] peek(io::Base.SecretBuffer, ::Type{UInt8}) in Base at secretbuffer.jl:157
[10] peek(s::IO, ::Type{T}) where T in Base at io.jl:254
[11] peek(s) in Base at io.jl:262

[cormullion]

Same output in a Plutonian cell...

[fonsp]

well this was a rollercoaster!

it looks like we have to pick a different function to abuse than Base.peek, since this one was changed and got added to the Julia spec. It made me realise that we should use a function that is already part of the Julia spec. My shortlist is:
Base.yield, Base.readlink, Base.get, Base.download, Base.zero. I'll sleep on it 😴

---

In the future, I'd like to add the possibility for bonds to transform the JavaScript-returned object before it is made available in the Julia scope. (See JuliaPluto/PlutoUI.jl#3 for motivation.) So you could overload:

Base.peek(x::MyBondType) = default_value

for the default value, and

Base.peek(x::MyBondType, received::Dict) = ...

is a 'preprocessor', the result of which is assigned to the bound variable.

If no overload exists for the first function, then Base.peek(x) = missing is used. For the second function, Base.peek(x, received) = received is the default. (These fallback methods are not added to the global scope)

[fonsp]

I think Base.get is best - it is closest to being semantically correct, and it is a commonly overloaded method.

I see use cases where package creators overload Base.get for their custom types for other reasons than the default-value-for-Pluto-bonds feature, (a Table type, for example, where the interaction is the clicked column), but:

1. Normal use of Base.get always takes 3 arguments, ours takes 1 or 2.
2. Overloading Base.get is not necessary for @bond support, they can ignore it if there's a conflict.
3. In the hard-to-imagine case that there is a conflict, the package creator can make JS return an object, and dispatch on Dict for the second argument. Or a singleton array and dispatch on Array{Dict} if Dict is the conflict. Or nested combinations even!

Let this be the only time that this API needs to change!

[fonsp]

The other option is to register a public AbstractPlutoBonds.jl package, but it's something I hope to avoid: We would be forcing a dependency upon other packages. Just like with the display system, I think that Julia's built-in features are good enough! Library packages should not depend on IDEs, and in Julia's case: packages should support rich output without depending/specializing on an IDE. Overloading a Base methods extends this concept to rich interactivity.

[cormullion]

I use get in my packages too - it seems nicely general... But I use 2 and 3 arguments... ¯\_(ツ)_/¯

[fonsp]

Alright lets do get!