Automatically disable older cells to solve multiple defs

[fonsp]

This PR adds some extra code into update_save_run! that checks, by comparing the old and new Topologys:

1. Did any of the cells (i.e. cells that the user wants to run) define a variable that was defined a fewer number of times in the old Topology?
2. For each such cell:
   a. Does cell define exactly one variable?
   b. Are all definers of that variable not in cells? i.e. did the other definitions appear in a previous run?
   c. Are no function definitions involved?
   d. Are there no macro calls? (TODO)
   e. Does cell not reference itself? (e.g. x = x+1)
   f. Then: disable all other definers of the variable.

This is done fully in backend, which makes it accurate!

Demo

This video demonstrates the basic functionality, and then a series of situations where we purposefully do not use this new feature.

Schermopname.2022-10-07.om.17.07.27.mov

Previous/related work

• Include set of disabled cells in NotebookTopology #2270
• 📎 Dynamic code hints: warn when creating a multiple definition #1859
• Allow solving multiple definitions by disabling one #2268
• Allow solving multiple definitions by disabling one, attempt 2 #2303

TODO

• Include set of disabled cells in NotebookTopology #2270
• Allow solving multiple definitions by disabling one, attempt 2 #2303
• Check if this is not too aggressive
• Add GUI to explain (what will happen and) what just happened
• Maybe make the criterea even more strict
• What about x = x + 1?
• Macro calls

[github-actions]

Try this Pull Request!

Open Julia and type:

julia> import Pkg
julia> Pkg.activate(temp=true)
julia> Pkg.add(url="https://github.com/fonsp/Pluto.jl", rev="auto-disable-multiple-definitions")
julia> using Pluto

[fonsp]

Now with GUI!

Schermopname.2022-10-14.om.19.39.58.mov