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REPL tips at startup.jl

This is my current (as of November 2023) .julia/config/startup.jl file:

using Revise
using BenchmarkTools
import OhMyREPL
OhMyREPL.colorscheme!("TomorrowNightBright")
import Pkg
Pkg.UPDATED_REGISTRY_THIS_SESSION[] = true
if occursin("v"*string(VERSION)[1:4],Base.active_project())
    Pkg.activate(temp=true)
end
  • Revise and BenchmarkTools are important development tools.
  • OhMyREPL is responsible for syntax highlighting in the REPL, and that is my preferred color scheme.

Install first these packages with:

julia> import Pkg; Pkg.add(["Revise", "BenchmarkTools", "OhMyREPL"])

With Pkg.UPDATE_REGISTRY_THIS_SESSION[] = true Julia will not try to download the latest version of every package all the time when installing a package in a new environment. This is nice to avoid many unnecessary downloading and recompilation runs.

The code

if occursin("v"*string(VERSION)[1:4],Base.active_project())
    Pkg.activate(temp=true)
end

will check if the active environment is the main one ("v1.10", or similar) and, in this case, activate a temporary environment instead. With that adding new packages does not bloat the Main environment. This is very convenient for testing new packages. Now (as of Julia 1.9) that precompiled cache files are saved, installing packages that are already locally available is quick, and thus having a default temporary environment is quite convenient.

A few time ago I used, instead of Pkg.activate(temp=true), 

insert!(LOAD_PATH, 2, mktempdir())

with which a temporary environment is added to the list of default environments. This is useful because, when installing a package automatically after a using Package command, one is prompted (by chossing the o) in which environment the package is to be installed. Choosing the tempororary one (which will be selected by default) will avoid clutering the global environment. In combination with the above update-registry option, this avoids may recompilation runs. But currently I prefer just always starting in a temporary environment.